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Seq	Timestamp	Type	Name	Duration
0/0	2026/10/26 02:25	flow	patch-triage	6m Args: null Results: { "EnableConfigs": [ "LIVEUPDATE", "KEXEC_HANDOVER", "LIVEUPDATE_MEMFD", "KEXEC_HANDOVER_ENABLE_DEFAULT" ], "FocusSymbols": [ "luo_session_freeze", "luo_file_freeze", "luo_file_unfreeze", "luo_session_preserve_fd", "luo_session_serialize" ], "KMSANReasoning": "The patch introduces the `LIVEUPDATE_SESSION_FREEZE` ioctl, allowing userspace to explicitly freeze a live-update session before kexec reboot.\n\nFrom a memory initialization and info-leak standpoint:\n1. User-kernel interface: The new ioctl parameter structure `struct liveupdate_session_freeze` consists of two `__u32` fields (`size` and `reserved`) with no structure padding (8 bytes total). In `luo_session_ioctl()`, input is copied and validated using `copy_struct_from_user()`, which zeroes any uncopied bytes within the kernel size. The ioctl response via `luo_ucmd_respond()` copies back the struct without exposing uninitialized stack or heap bytes.\n2. Internal state and structures: `struct luo_session` is allocated via `kzalloc_obj()`, ensuring the newly added `bool user_frozen` field is initialized to false. KHO serialization buffers are allocated using `kho_alloc_preserve()`, which zeroes allocated memory.\n3. Bug surface: The primary risks associated with this patch involve session state transitions, lifecycle management (freeze/unfreeze on error/release), concurrency (guarded by mutex and rwsem), or error handling logic. Such bugs (e.g. use-after-free, double free, locking anomalies) are fully covered by KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nBecause no uninitialized memory reads or information leak hazards are introduced, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false, "Reasoning": "The patch introduces the LIVEUPDATE_SESSION_FREEZE ioctl to the Live Update Orchestrator (LUO) subsystem. This allows userspace to explicitly freeze session files and serialize metadata before kexec reboot. The changes modify session state handling, error recovery/rollback paths, file handler freezing/unfreezing, and session release logic. The code is exposed via the /dev/liveupdate character device and session file descriptors, making it fully reachable and testable in virtualized environments without requiring specialized physical hardware.", "WorthFuzzing": true }
1/1	2026/10/26 02:25	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 0756a3f342510e16a8b645b5dd51139b212e6a81\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Mon Oct 26 02:25:46 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h\nindex 6051abc0612ce..851692571e130 100644\n--- a/include/linux/liveupdate.h\n+++ b/include/linux/liveupdate.h\n@@ -59,7 +59,8 @@ struct liveupdate_file_op_args {\n * compatible with the given file.\n * @preserve: Required. Performs state-saving for the file.\n * @unpreserve: Required. Cleans up any resources allocated by @preserve.\n- * @freeze: Optional. Final actions just before kernel transition.\n+ * @freeze: Optional. Prepares final state before kexec (via\n+ * LIVEUPDATE_SESSION_FREEZE or during reboot).\n * @unfreeze: Optional. Undo freeze operations.\n * @retrieve: Required. Restores the file in the new kernel.\n * @can_finish: Optional. Check if this FD can finish, i.e. all restoration\ndiff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h\nindex 4043d40387125..3fb0cae0f7112 100644\n--- a/include/uapi/linux/liveupdate.h\n+++ b/include/uapi/linux/liveupdate.h\n@@ -60,6 +60,7 @@ enum {\n \tLIVEUPDATE_CMD_SESSION_RETRIEVE_FD = 0x41,\n \tLIVEUPDATE_CMD_SESSION_FINISH = 0x42,\n \tLIVEUPDATE_CMD_SESSION_GET_NAME = 0x43,\n+\tLIVEUPDATE_CMD_SESSION_FREEZE = 0x44,\n };\n \n /\n@@ -236,4 +237,28 @@ struct liveupdate_session_get_name {\n #define LIVEUPDATE_SESSION_GET_NAME\t\t\t\t\t\\\n \t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_NAME)\n \n+/\n+ * struct liveupdate_session_freeze - ioctl(LIVEUPDATE_SESSION_FREEZE)\n+ * @size: Input; sizeof(struct liveupdate_session_freeze)\n+ * @reserved: Input; Must be zero. Reserved for future use.\n+ \n+ Freezes the session from userspace before the kexec reboot phase.\n+ \n+ When this ioctl is called, the kernel executes the .freeze() callback on all\n+ * preserved files in the session and serializes their metadata. Once frozen,\n+ * no further files can be preserved in the session.\n+ \n+ During the subsequent kexec reboot, this session is recognized as already\n+ * frozen and is skipped from the late auto freeze.\n+ \n+ Return: 0 on success, negative error code on failure.\n+ /\n+struct liveupdate_session_freeze {\n+\t__u32\t\tsize;\n+\t__u32\t\treserved;\n+};\n+\n+#define LIVEUPDATE_SESSION_FREEZE\t\t\t\t\t\\\n+\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_FREEZE)\n+\n #endif / _UAPI_LIVEUPDATE_H /\ndiff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c\nindex a39992da504fb..fac2e5a6bdc06 100644\n--- a/kernel/liveupdate/luo_file.c\n+++ b/kernel/liveupdate/luo_file.c\n@@ -31,9 +31,9 @@\n - unpreserve(): Cleans up any resources allocated by .preserve(), called\n * if the preservation process is aborted before the reboot (i.e. session is\n * closed).\n- * - freeze(): A final pre-reboot opportunity to prepare the state for kexec.\n- * We are already in reboot syscall, and therefore userspace cannot mutate\n- * the file anymore.\n+ * - freeze(): Prepares the final state for kexec. Invoked either via\n+ * the LIVEUPDATE_SESSION_FREEZE ioctl once userspace is done modifying\n+ * the session's files, or during the reboot() syscall.\n * - unfreeze(): Undoes the actions of .freeze(), called if the live update\n * is aborted after the freeze phase.\n * - retrieve(): Reconstructs the file in the new kernel from the preserved\n@@ -48,7 +48,8 @@\n * handler, calls its .preserve() operation, and creates an internal \u0026struct\n * luo_file to track the live state.\n \n- 2. Freeze (Pre-Reboot): Just before the kexec, luo_file_freeze() is called.\n+ * 2. Freeze (Pre-Reboot): Either explicitly via LIVEUPDATE_SESSION_FREEZE or\n+ * just before the kexec during reboot(), luo_file_freeze() is called.\n * It iterates through all preserved files, calls their respective .freeze()\n * operation, and serializes their final metadata (compatible string, token,\n * and data handle) into a contiguous memory block for KHO.\n@@ -74,15 +75,16 @@\n \n 1. Abort Before Reboot: If the userspace agent aborts the live update\n * process before calling reboot (e.g., by closing the session file\n- * descriptor), the session's release handler calls\n- * luo_file_unpreserve_files(). This invokes the .unpreserve() callback on\n- * all preserved files, ensuring all allocated resources are cleaned up and\n- * returning the system to a clean state.\n+ * descriptor), the session's release handler unfreezes the files if the\n+ * session was already frozen and calls luo_file_unpreserve_files(). This\n+ * invokes the .unpreserve() callback on all preserved files, ensuring all\n+ * allocated resources are cleaned up and returning the system to a clean\n+ * state.\n \n- 2. Freeze Failure: During the reboot() syscall, if any handler's .freeze()\n- * op fails, the .unfreeze() op is invoked on all previously successful\n- * freezes to roll back their state. The reboot() syscall then returns an\n- * error to userspace, canceling the live update.\n+ * 2. Freeze Failure: During LIVEUPDATE_SESSION_FREEZE or the reboot() syscall,\n+ * if any handler's .freeze() op fails, the .unfreeze() op is invoked on all\n+ * previously successful freezes to roll back their state, and an error is\n+ * returned to userspace, canceling the live update if called from reboot().\n \n 3. Finish Failure: In the new kernel, if a handler's .finish() op fails,\n * the luo_file_finish() operation is aborted. LUO retains ownership of\n@@ -440,12 +442,11 @@ static void __luo_file_unfreeze(struct luo_file_set file_set,\n \n /\n luo_file_freeze - Freezes all preserved files and serializes their metadata.\n- * @file_set: The file_set whose files are to be frozen.\n- * @file_set_ser: Where to put the serialized file_set.\n+ * @file_set: The file_set whose files are to be frozen.\n \n- This function is called from the reboot() syscall path, just before the\n- * kernel transitions to the new image via kexec. Its purpose is to perform the\n- * final preparation and serialization of all preserved files in the file_set.\n+ * This function is called from LIVEUPDATE_SESSION_FREEZE or from the reboot()\n+ * syscall path. Its purpose is to perform the final preparation and\n+ * serialization of all preserved files in the file_set.\n \n It iterates through each preserved file in FIFO order (the order of\n * preservation) and performs two main actions:\n@@ -457,22 +458,20 @@ static void __luo_file_unfreeze(struct luo_file_set file_set,\n \n * 2. Serializes Metadata: After a successful freeze, it copies the final file\n * metadata—the handler's compatible string, the user token, and the final\n- * private data handle—into the pre-allocated contiguous memory buffer\n- * (file_set-\u003efiles) that will be handed over to the next kernel via KHO.\n+ * private data handle—into the pre-allocated serialization blocks\n+ * (file_set-\u003eblock_set) that will be handed over to the next kernel via KHO.\n \n Error Handling (Rollback):\n * This function is atomic. If any handler's .freeze() operation fails, the\n- * entire live update is aborted. The __luo_file_unfreeze() helper is\n- * immediately called to invoke the .unfreeze() op on all files that were\n- * successfully frozen before the point of failure, rolling them back to a\n- * running state. The function then returns an error, causing the reboot()\n- * syscall to fail.\n+ * __luo_file_unfreeze() helper is immediately called to invoke the .unfreeze()\n+ * op on all files that were successfully frozen before the point of failure,\n+ * rolling them back to an unfrozen state, and an error is returned to the\n+ * caller, canceling the live update if called from the reboot() path.\n \n- Context: Called only from the liveupdate_reboot() path.\n+ * Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path.\n * Return: 0 on success, or a negative errno on failure.\n /\n-int luo_file_freeze(struct luo_file_set file_set,\n-\t\t struct luo_file_set_ser file_set_ser)\n+int luo_file_freeze(struct luo_file_set file_set)\n {\n \tstruct luo_file luo_file;\n \tstruct kho_block_set_it it;\n@@ -506,9 +505,6 @@ int luo_file_freeze(struct luo_file_set file_set,\n \t\tfile_ser-\u003etoken = luo_file-\u003etoken;\n \t}\n \n-\tfile_set_ser-\u003ecount = file_set-\u003ecount;\n-\tfile_set_ser-\u003efiles = kho_block_set_head_pa(\u0026file_set-\u003eblock_set);\n-\n \treturn 0;\n \n err_unfreeze:\n@@ -519,28 +515,25 @@ int luo_file_freeze(struct luo_file_set file_set,\n \n /\n luo_file_unfreeze - Unfreezes all files in a file_set and clear serialization\n- * @file_set: The file_set whose files are to be unfrozen.\n- * @file_set_ser: Serialized file_set.\n+ * @file_set: The file_set whose files are to be unfrozen.\n \n This function rolls back the state of all files in a file_set after the\n- * freeze phase has begun but must be aborted. It is the counterpart to\n- * luo_file_freeze().\n+ * freeze phase has begun. It is the counterpart to luo_file_freeze().\n \n It invokes the __luo_file_unfreeze() helper with a NULL argument, which\n- * signals the helper to iterate through all files in the file_set and call\n- * their respective .unfreeze() handler callbacks.\n+ * signals the helper to iterate through all files in the file_set, call their\n+ * respective .unfreeze() handler callbacks, and clear the serialized blocks.\n \n Context: This is called when the live update is aborted during\n- * the reboot() syscall, after luo_file_freeze() has been called.\n+ * the reboot() syscall, after luo_file_freeze() has been called,\n+ * or when an explicitly frozen session is released before kexec.\n /\n-void luo_file_unfreeze(struct luo_file_set file_set,\n-\t\t struct luo_file_set_ser file_set_ser)\n+void luo_file_unfreeze(struct luo_file_set file_set)\n {\n \tif (!file_set-\u003ecount)\n \t\treturn;\n \n \t__luo_file_unfreeze(file_set, NULL);\n-\tmemset(file_set_ser, 0, sizeof(file_set_ser));\n }\n \n /\ndiff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h\nindex dac6644bfb18a..381499e73d2ac 100644\n--- a/kernel/liveupdate/luo_internal.h\n+++ b/kernel/liveupdate/luo_internal.h\n@@ -64,6 +64,8 @@ struct luo_file_set {\n previous kernel) sessions.\n * @retrieved: A boolean flag indicating whether this session has been\n * retrieved by a consumer in the new kernel.\n+ * @user_frozen: A boolean flag indicating whether this session has been\n+ * frozen explicitly from userspace.\n * @file_set: A set of files that belong to this session.\n * @mutex: protects fields in the luo_session.\n /\n@@ -71,6 +73,7 @@ struct luo_session {\n \tchar name[LIVEUPDATE_SESSION_NAME_LENGTH];\n \tstruct list_head list;\n \tbool retrieved;\n+\tbool user_frozen;\n \tstruct luo_file_set file_set;\n \tstruct mutex mutex;\n };\n@@ -103,10 +106,8 @@ int luo_session_deserialize(void);\n \n int luo_preserve_file(struct luo_file_set file_set, u64 token, int fd);\n void luo_file_unpreserve_files(struct luo_file_set file_set);\n-int luo_file_freeze(struct luo_file_set file_set,\n-\t\t struct luo_file_set_ser file_set_ser);\n-void luo_file_unfreeze(struct luo_file_set file_set,\n-\t\t struct luo_file_set_ser file_set_ser);\n+int luo_file_freeze(struct luo_file_set file_set);\n+void luo_file_unfreeze(struct luo_file_set file_set);\n int luo_retrieve_file(struct luo_file_set file_set, u64 token,\n \t\t struct file *filep);\n int luo_file_finish(struct luo_file_set file_set);\ndiff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c\nindex f48e9a4185f97..cce6d09280b3e 100644\n--- a/kernel/liveupdate/luo_session.c\n+++ b/kernel/liveupdate/luo_session.c\n@@ -34,10 +34,11 @@\n * 1. Creation: A userspace agent calls `luo_session_create()` to create a\n * new, empty session and receives a file descriptor for it.\n \n- 2. Serialization: When the `reboot(LINUX_REBOOT_CMD_KEXEC)` syscall is\n- * made, `luo_session_serialize()` is called. It iterates through all\n- * active sessions and writes their metadata into a memory area preserved\n- * by KHO.\n+ * 2. Freeze / Serialization: Sessions may be frozen explicitly from userspace\n+ * via `LIVEUPDATE_SESSION_FREEZE`. When the `reboot(LINUX_REBOOT_CMD_KEXEC)`\n+ * syscall is made, `luo_session_serialize()` is called to freeze any\n+ * remaining active sessions and write all session metadata into a memory\n+ * area preserved by KHO.\n \n 3. Deserialization (in new kernel): After kexec, `luo_session_deserialize()`\n * runs, reading the serialized data and creating a list of `struct\n@@ -218,18 +219,38 @@ static int luo_session_finish_one(struct luo_session session)\n \treturn luo_file_finish(\u0026session-\u003efile_set);\n }\n \n-static void luo_session_unfreeze_one(struct luo_session session,\n-\t\t\t\t struct luo_session_ser ser)\n+static void luo_session_unserialize_one(struct luo_session session,\n+\t\t\t\t\tstruct luo_session_ser ser)\n {\n \tguard(mutex)(\u0026session-\u003emutex);\n-\tluo_file_unfreeze(\u0026session-\u003efile_set, \u0026ser-\u003efile_set_ser);\n+\t/\n+\t * Only unfreeze sessions that were auto-frozen by\n+\t * luo_session_serialize_one(); sessions frozen explicitly by\n+\t * userspace stay frozen until the session FD is closed.\n+\t /\n+\tif (!session-\u003euser_frozen)\n+\t\tluo_file_unfreeze(\u0026session-\u003efile_set);\n+\tmemset(ser, 0, sizeof(ser));\n }\n \n-static int luo_session_freeze_one(struct luo_session session,\n-\t\t\t\t struct luo_session_ser ser)\n+static int luo_session_serialize_one(struct luo_session session,\n+\t\t\t\t struct luo_session_ser ser)\n {\n+\tint err;\n+\n \tguard(mutex)(\u0026session-\u003emutex);\n-\treturn luo_file_freeze(\u0026session-\u003efile_set, \u0026ser-\u003efile_set_ser);\n+\tif (!session-\u003euser_frozen) {\n+\t\terr = luo_file_freeze(\u0026session-\u003efile_set);\n+\t\tif (err)\n+\t\t\treturn err;\n+\t}\n+\n+\tstrscpy(ser-\u003ename, session-\u003ename, sizeof(ser-\u003ename));\n+\tser-\u003efile_set_ser.count = session-\u003efile_set.count;\n+\tser-\u003efile_set_ser.files =\n+\t\tkho_block_set_head_pa(\u0026session-\u003efile_set.block_set);\n+\n+\treturn 0;\n }\n \n static int luo_session_release(struct inode inodep, struct file filep)\n@@ -249,8 +270,11 @@ static int luo_session_release(struct inode inodep, struct file filep)\n \t\t}\n \t\tsh = \u0026luo_session_global.incoming;\n \t} else {\n-\t\tscoped_guard(mutex, \u0026session-\u003emutex)\n+\t\tscoped_guard(mutex, \u0026session-\u003emutex) {\n+\t\t\tif (session-\u003euser_frozen)\n+\t\t\t\tluo_file_unfreeze(\u0026session-\u003efile_set);\n \t\t\tluo_file_unpreserve_files(\u0026session-\u003efile_set);\n+\t\t}\n \t\tsh = \u0026luo_session_global.outgoing;\n \t}\n \n@@ -267,6 +291,9 @@ static int luo_session_preserve_fd(struct luo_session session,\n \tint err;\n \n \tguard(mutex)(\u0026session-\u003emutex);\n+\tif (session-\u003euser_frozen)\n+\t\treturn -EBUSY;\n+\n \terr = luo_preserve_file(\u0026session-\u003efile_set, argp-\u003etoken, argp-\u003efd);\n \tif (err)\n \t\treturn err;\n@@ -340,11 +367,40 @@ static int luo_session_get_name(struct luo_session session,\n \treturn luo_ucmd_respond(ucmd, sizeof(argp));\n }\n \n+static int luo_session_freeze(struct luo_session session,\n+\t\t\t struct luo_ucmd ucmd)\n+{\n+\tstruct liveupdate_session_freeze argp = ucmd-\u003ecmd;\n+\tint err;\n+\n+\tif (argp-\u003ereserved)\n+\t\treturn -EINVAL;\n+\n+\tguard(mutex)(\u0026session-\u003emutex);\n+\tif (session-\u003euser_frozen)\n+\t\treturn -EBUSY;\n+\n+\terr = luo_file_freeze(\u0026session-\u003efile_set);\n+\tif (err)\n+\t\treturn err;\n+\n+\terr = luo_ucmd_respond(ucmd, sizeof(argp));\n+\tif (err) {\n+\t\tluo_file_unfreeze(\u0026session-\u003efile_set);\n+\t\treturn err;\n+\t}\n+\n+\tsession-\u003euser_frozen = true;\n+\n+\treturn 0;\n+}\n+\n union ucmd_buffer {\n \tstruct liveupdate_session_finish finish;\n \tstruct liveupdate_session_preserve_fd preserve;\n \tstruct liveupdate_session_retrieve_fd retrieve;\n \tstruct liveupdate_session_get_name get_name;\n+\tstruct liveupdate_session_freeze freeze;\n };\n \n / Type of sessions the ioctl applies to. /\n@@ -382,6 +438,8 @@ static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\n \t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),\n \tIOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,\n \t\t struct liveupdate_session_get_name, name, LUO_IOCTL_ALL),\n+\tIOCTL_OP(LIVEUPDATE_SESSION_FREEZE, luo_session_freeze,\n+\t\t struct liveupdate_session_freeze, reserved, LUO_IOCTL_OUTGOING),\n };\n \n static bool luo_ioctl_type_valid(struct luo_session session,\n@@ -656,13 +714,11 @@ int luo_session_serialize(void)\n \t\t\tgoto err_undo;\n \t\t}\n \n-\t\terr = luo_session_freeze_one(session, ser);\n+\t\terr = luo_session_serialize_one(session, ser);\n \t\tif (err) {\n \t\t\tkho_block_set_it_prev(\u0026it);\n \t\t\tgoto err_undo;\n \t\t}\n-\n-\t\tstrscpy(ser-\u003ename, session-\u003ename, sizeof(ser-\u003ename));\n \t}\n \n \tif (sh-\u003ecount \u003e 0)\n@@ -675,8 +731,7 @@ int luo_session_serialize(void)\n \tlist_for_each_entry_continue_reverse(session, \u0026sh-\u003elist, list) {\n \t\tstruct luo_session_ser ser = kho_block_set_it_prev(\u0026it);\n \n-\t\tluo_session_unfreeze_one(session, ser);\n-\t\tmemset(ser-\u003ename, 0, sizeof(ser-\u003ename));\n+\t\tluo_session_unserialize_one(session, ser);\n \t}\n \tup_write(\u0026sh-\u003erwsem);\n \tup_write(\u0026luo_session_serialize_rwsem);\ndiff --git a/mm/memfd_luo.c b/mm/memfd_luo.c\nindex 6b68220275ebe..a3bf872b3a03f 100644\n--- a/mm/memfd_luo.c\n+++ b/mm/memfd_luo.c\n@@ -43,8 +43,9 @@\n allocating pages for them during preservation.\n \n File Position\n- * The current file position is preserved, allowing applications to continue\n- * reading/writing from their last position.\n+ * The file position at the time the session is frozen is preserved,\n+ * allowing applications to continue reading/writing from their last\n+ * position.\n \n File Status Flags\n * memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property\ndiff --git a/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h b/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h\nindex fa07fed083646..15a7db3a6b3e8 100644\n--- a/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h\n+++ b/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h\n@@ -26,6 +26,7 @@ int luo_create_session(int luo_fd, const char name);\n int luo_retrieve_session(int luo_fd, const char name);\n int luo_session_finish(int session_fd);\n int luo_get_session_name(int session_fd, char name, size_t name_len);\n+int luo_session_freeze(int session_fd);\n \n int luo_ensure_nofile_limit(long min_limit);\n int luo_session_preserve_fd(int session_fd, int fd, __u64 token);\ndiff --git a/tools/testing/selftests/liveupdate/lib/lu_utils.c b/tools/testing/selftests/liveupdate/lib/lu_utils.c\nindex 74d41115c2815..6315746ff08f8 100644\n--- a/tools/testing/selftests/liveupdate/lib/lu_utils.c\n+++ b/tools/testing/selftests/liveupdate/lib/lu_utils.c\n@@ -198,6 +198,16 @@ int luo_session_finish(int session_fd)\n \treturn 0;\n }\n \n+int luo_session_freeze(int session_fd)\n+{\n+\tstruct liveupdate_session_freeze arg = { .size = sizeof(arg) };\n+\n+\tif (ioctl(session_fd, LIVEUPDATE_SESSION_FREEZE, \u0026arg) \u003c 0)\n+\t\treturn -errno;\n+\n+\treturn 0;\n+}\n+\n void create_state_file(int luo_fd, const char session_name, int token,\n \t\t int next_stage)\n {\ndiff --git a/tools/testing/selftests/liveupdate/liveupdate.c b/tools/testing/selftests/liveupdate/liveupdate.c\nindex 2dedd5fc2534f..c27f57eab8707 100644\n--- a/tools/testing/selftests/liveupdate/liveupdate.c\n+++ b/tools/testing/selftests/liveupdate/liveupdate.c\n@@ -530,4 +530,49 @@ TEST_F(liveupdate_device, preserve_many_files)\n \tASSERT_EQ(close(session_fd), 0);\n }\n \n+/\n+ Test Case: Session Freeze\n+ \n+ Verifies the LIVEUPDATE_SESSION_FREEZE ioctl on an outgoing session.\n+ /\n+TEST_F(liveupdate_device, session_freeze)\n+{\n+\tstruct liveupdate_session_freeze bad_arg = {\n+\t\t.size = sizeof(bad_arg),\n+\t\t.reserved = 1,\n+\t};\n+\tint session_fd, mem_fd1, mem_fd2;\n+\n+\tself-\u003efd1 = open(LIVEUPDATE_DEV, O_RDWR);\n+\tif (self-\u003efd1 \u003c 0 \u0026\u0026 errno == ENOENT)\n+\t\tSKIP(return, \"%s does not exist\", LIVEUPDATE_DEV);\n+\tASSERT_GE(self-\u003efd1, 0);\n+\n+\tsession_fd = luo_create_session(self-\u003efd1, \"session-freeze-test\");\n+\tASSERT_GE(session_fd, 0);\n+\n+\tmem_fd1 = memfd_create(\"freeze-memfd-1\", 0);\n+\tASSERT_GE(mem_fd1, 0);\n+\tASSERT_EQ(luo_session_preserve_fd(session_fd, mem_fd1, 0x1111), 0);\n+\n+\t/ Non-zero reserved field must fail with -EINVAL /\n+\tEXPECT_EQ(ioctl(session_fd, LIVEUPDATE_SESSION_FREEZE, \u0026bad_arg), -1);\n+\tEXPECT_EQ(errno, EINVAL);\n+\n+\t/ Freeze the session early /\n+\tASSERT_EQ(luo_session_freeze(session_fd), 0);\n+\n+\t/ Subsequent freeze attempt on an already frozen session must fail with -EBUSY /\n+\tEXPECT_EQ(luo_session_freeze(session_fd), -EBUSY);\n+\n+\t/ Preserving a file after freeze must fail with -EBUSY */\n+\tmem_fd2 = memfd_create(\"freeze-memfd-2\", 0);\n+\tASSERT_GE(mem_fd2, 0);\n+\tEXPECT_EQ(luo_session_preserve_fd(session_fd, mem_fd2, 0x2222), -EBUSY);\n+\n+\tASSERT_EQ(close(session_fd), 0);\n+\tASSERT_EQ(close(mem_fd1), 0);\n+\tASSERT_EQ(close(mem_fd2), 0);\n+}\n+\n TEST_HARNESS_MAIN\ndiff --git a/tools/testing/selftests/liveupdate/luo_kexec_simple.c b/tools/testing/selftests/liveupdate/luo_kexec_simple.c\nindex 786ac93b9ae38..9bc8dab2e074c 100644\n--- a/tools/testing/selftests/liveupdate/luo_kexec_simple.c\n+++ b/tools/testing/selftests/liveupdate/luo_kexec_simple.c\n@@ -40,6 +40,11 @@ static void run_stage_1(int luo_fd)\n \t\t\t TEST_MEMFD_TOKEN);\n \t}\n \n+\tksft_print_msg(\"[STAGE 1] Freezing session '%s' early...\\n\",\n+\t\t TEST_SESSION_NAME);\n+\tif (luo_session_freeze(session_fd) \u003c 0)\n+\t\tfail_exit(\"luo_session_freeze for '%s'\", TEST_SESSION_NAME);\n+\n \tclose(luo_fd);\n \tdaemonize_and_wait();\n }\n@@ -60,6 +65,9 @@ static void run_stage_2(int luo_fd, int state_session_fd)\n \tif (session_fd \u003c 0)\n \t\tfail_exit(\"luo_retrieve_session for '%s'\", TEST_SESSION_NAME);\n \n+\tif (luo_session_freeze(session_fd) != -EINVAL)\n+\t\tfail_exit(\"luo_session_freeze on incoming session did not return -EINVAL\");\n+\n \tksft_print_msg(\"[STAGE 2] Restoring and verifying memfd (token %#x)...\\n\",\n \t\t TEST_MEMFD_TOKEN);\n \tmfd = restore_and_verify_memfd(session_fd, TEST_MEMFD_TOKEN,\n" }
2/1	2026/10/26 02:25	agent	patch-evaluator	3m Model: core Args: null Results: { "EnableConfigs": [ "LIVEUPDATE", "KEXEC_HANDOVER", "LIVEUPDATE_MEMFD", "KEXEC_HANDOVER_ENABLE_DEFAULT" ], "FocusSymbols": [ "luo_session_freeze", "luo_file_freeze", "luo_file_unfreeze", "luo_session_preserve_fd", "luo_session_serialize" ], "Reasoning": "The patch introduces the LIVEUPDATE_SESSION_FREEZE ioctl to the Live Update Orchestrator (LUO) subsystem. This allows userspace to explicitly freeze session files and serialize metadata before kexec reboot. The changes modify session state handling, error recovery/rollback paths, file handler freezing/unfreezing, and session release logic. The code is exposed via the /dev/liveupdate character device and session file descriptors, making it fully reachable and testable in virtualized environments without requiring specialized physical hardware.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer and security engineer. Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on internal assumptions. You must actively use your code access tools to inspect the actual source code, callers, and surrounding context. ================================================================================ 1. CORE TRIAGE PHILOSOPHY ================================================================================ The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions introduced by the patch series. - REACHABILITY IS THE PRIMARY GATE: Fuzzing can only discover bugs in code that can actually execute in standard virtualized environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap). If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed, regardless of whether it adds assertions or complex logic. - DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS: Patch authors routinely label changes as "cleanups", "refactorings", or state "No functional change intended". Do NOT take these claims at face value. Code refactorings that rearrange logic, introduce helper functions, or alter state management in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs. If reachable executable code is modified or refactored, it MUST be fuzzed. - NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED: When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON, VM_WARN_ON, BUG_ON, lockdep_assert) in reachable code paths, it enforces new or stricter invariants. Even if the author believes the invariant always holds, fuzzing is essential to verify whether an unusual sequence of operations can violate it. ================================================================================ 2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA) ================================================================================ Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories: - Non-kernel and non-executable changes: * Modifications to Documentation/, comments, or spelling fixes. * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/) that do not affect the compiled kernel image (vmlinux) or kernel modules. * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints that do not alter control flow or data structures. * Build system or Kconfig changes that do not alter compiled C logic. - Structurally unreachable hardware: * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU. - Unreachable execution paths: * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during physical PCI hot-unplug or manual sysfs driver unbinding. * Code paths exclusive to architectures other than the target architecture. ================================================================================ 3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA) ================================================================================ Return WorthFuzzing=true whenever the patch touches reachable executable code, including: - Core Subsystems: * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/), BPF, scheduler, core networking, VFS, or syscall handling. - Refactorings and Code Cleanups: * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. - Runtime Assertions and Defensive Checks: * Any introduction or alteration of assertions (WARN_ON, VM_WARN_ON, BUG_ON, etc.) in reachable paths. - Reachable Drivers and Protocols: Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.). ================================================================================ 4. EXTRACTING FocusSymbols (PREVENTING DILUTION) ================================================================================ When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer: - AVOID UBIQUITOUS LIFECYCLE HOT-PATHS: Do NOT list generic, ubiquitous functions called by almost every program in the corpus (including, but not limited to: general memory allocators and deallocators, page fault and trap handlers, or core synchronization primitives; this is not an exhaustive list). Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused", which severely dilutes fuzzing effort away from the actual changes. - TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS: List functions that specifically implement the logic being added or altered, or direct API entrypoints for the subsystem feature under review. - HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h): Compiler-inlined static functions (such as static inlines in mm/.h or include/linux/.h) lack distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters. If the changes are primarily in static inline helpers, identify non-static, feature-specific caller functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers). ================================================================================ 5. IDENTIFYING EnableConfigs ================================================================================ Identify any specific CONFIG_ options required to properly compile and reach the modified code: - Inspect Kconfig files and #ifdef guards; do not make assumptions. - Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed. - Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 0756a3f342510e16a8b645b5dd51139b212e6a81 Author: syz-cluster <triage@syzkaller.com> Date: Mon Oct 26 02:25:46 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h index 6051abc0612ce..851692571e130 100644 --- a/include/linux/liveupdate.h +++ b/include/linux/liveupdate.h @@ -59,7 +59,8 @@ struct liveupdate_file_op_args { * compatible with the given file. * @preserve: Required. Performs state-saving for the file. * @unpreserve: Required. Cleans up any resources allocated by @preserve. - * @freeze: Optional. Final actions just before kernel transition. + * @freeze: Optional. Prepares final state before kexec (via + * LIVEUPDATE_SESSION_FREEZE or during reboot). * @unfreeze: Optional. Undo freeze operations. * @retrieve: Required. Restores the file in the new kernel. * @can_finish: Optional. Check if this FD can finish, i.e. all restoration diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h index 4043d40387125..3fb0cae0f7112 100644 --- a/include/uapi/linux/liveupdate.h +++ b/include/uapi/linux/liveupdate.h @@ -60,6 +60,7 @@ enum { LIVEUPDATE_CMD_SESSION_RETRIEVE_FD = 0x41, LIVEUPDATE_CMD_SESSION_FINISH = 0x42, LIVEUPDATE_CMD_SESSION_GET_NAME = 0x43, + LIVEUPDATE_CMD_SESSION_FREEZE = 0x44, }; / @@ -236,4 +237,28 @@ struct liveupdate_session_get_name { #define LIVEUPDATE_SESSION_GET_NAME \ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_NAME) +/ + * struct liveupdate_session_freeze - ioctl(LIVEUPDATE_SESSION_FREEZE) + * @size: Input; sizeof(struct liveupdate_session_freeze) + * @reserved: Input; Must be zero. Reserved for future use. + * + * Freezes the session from userspace before the kexec reboot phase. + * + * When this ioctl is called, the kernel executes the .freeze() callback on all + * preserved files in the session and serializes their metadata. Once frozen, + * no further files can be preserved in the session. + * + * During the subsequent kexec reboot, this session is recognized as already + * frozen and is skipped from the late auto freeze. + * + * Return: 0 on success, negative error code on failure. + / +struct liveupdate_session_freeze { + __u32 size; + __u32 reserved; +}; + +#define LIVEUPDATE_SESSION_FREEZE \ + _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_FREEZE) + #endif / _UAPI_LIVEUPDATE_H / diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c index a39992da504fb..fac2e5a6bdc06 100644 --- a/kernel/liveupdate/luo_file.c +++ b/kernel/liveupdate/luo_file.c @@ -31,9 +31,9 @@ - unpreserve(): Cleans up any resources allocated by .preserve(), called * if the preservation process is aborted before the reboot (i.e. session is * closed). - * - freeze(): A final pre-reboot opportunity to prepare the state for kexec. - * We are already in reboot syscall, and therefore userspace cannot mutate - * the file anymore. + * - freeze(): Prepares the final state for kexec. Invoked either via + * the LIVEUPDATE_SESSION_FREEZE ioctl once userspace is done modifying + * the session's files, or during the reboot() syscall. * - unfreeze(): Undoes the actions of .freeze(), called if the live update * is aborted after the freeze phase. * - retrieve(): Reconstructs the file in the new kernel from the preserved @@ -48,7 +48,8 @@ * handler, calls its .preserve() operation, and creates an internal &struct * luo_file to track the live state. * - * 2. Freeze (Pre-Reboot): Just before the kexec, luo_file_freeze() is called. + * 2. Freeze (Pre-Reboot): Either explicitly via LIVEUPDATE_SESSION_FREEZE or + * just before the kexec during reboot(), luo_file_freeze() is called. * It iterates through all preserved files, calls their respective .freeze() * operation, and serializes their final metadata (compatible string, token, * and data handle) into a contiguous memory block for KHO. @@ -74,15 +75,16 @@ * * 1. Abort Before Reboot: If the userspace agent aborts the live update * process before calling reboot (e.g., by closing the session file - * descriptor), the session's release handler calls - * luo_file_unpreserve_files(). This invokes the .unpreserve() callback on - * all preserved files, ensuring all allocated resources are cleaned up and - * returning the system to a clean state. + * descriptor), the session's release handler unfreezes the files if the + * session was already frozen and calls luo_file_unpreserve_files(). This + * invokes the .unpreserve() callback on all preserved files, ensuring all + * allocated resources are cleaned up and returning the system to a clean + * state. * - * 2. Freeze Failure: During the reboot() syscall, if any handler's .freeze() - * op fails, the .unfreeze() op is invoked on all previously successful - * freezes to roll back their state. The reboot() syscall then returns an - * error to userspace, canceling the live update. + * 2. Freeze Failure: During LIVEUPDATE_SESSION_FREEZE or the reboot() syscall, + * if any handler's .freeze() op fails, the .unfreeze() op is invoked on all + * previously successful freezes to roll back their state, and an error is + * returned to userspace, canceling the live update if called from reboot(). * * 3. Finish Failure: In the new kernel, if a handler's .finish() op fails, * the luo_file_finish() operation is aborted. LUO retains ownership of @@ -440,12 +442,11 @@ static void __luo_file_unfreeze(struct luo_file_set file_set, /* * luo_file_freeze - Freezes all preserved files and serializes their metadata. - * @file_set: The file_set whose files are to be frozen. - * @file_set_ser: Where to put the serialized file_set. + * @file_set: The file_set whose files are to be frozen. * - * This function is called from the reboot() syscall path, just before the - * kernel transitions to the new image via kexec. Its purpose is to perform the - * final preparation and serialization of all preserved files in the file_set. + * This function is called from LIVEUPDATE_SESSION_FREEZE or from the reboot() + * syscall path. Its purpose is to perform the final preparation and + * serialization of all preserved files in the file_set. * * It iterates through each preserved file in FIFO order (the order of * preservation) and performs two main actions: @@ -457,22 +458,20 @@ static void __luo_file_unfreeze(struct luo_file_set file_set, * 2. Serializes Metadata: After a successful freeze, it copies the final file * metadata—the handler's compatible string, the user token, and the final - * private data handle—into the pre-allocated contiguous memory buffer - * (file_set->files) that will be handed over to the next kernel via KHO. + * private data handle—into the pre-allocated serialization blocks + * (file_set->block_set) that will be handed over to the next kernel via KHO. * * Error Handling (Rollback): * This function is atomic. If any handler's .freeze() operation fails, the - * entire live update is aborted. The __luo_file_unfreeze() helper is - * immediately called to invoke the .unfreeze() op on all files that were - * successfully frozen before the point of failure, rolling them back to a - * running state. The function then returns an error, causing the reboot() - * syscall to fail. + * __luo_file_unfreeze() helper is immediately called to invoke the .unfreeze() + * op on all files that were successfully frozen before the point of failure, + * rolling them back to an unfrozen state, and an error is returned to the + * caller, canceling the live update if called from the reboot() path. * - * Context: Called only from the liveupdate_reboot() path. + * Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path. * Return: 0 on success, or a negative errno on failure. / -int luo_file_freeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser) +int luo_file_freeze(struct luo_file_set file_set) { struct luo_file luo_file; struct kho_block_set_it it; @@ -506,9 +505,6 @@ int luo_file_freeze(struct luo_file_set file_set, file_ser->token = luo_file->token; } - file_set_ser->count = file_set->count; - file_set_ser->files = kho_block_set_head_pa(&file_set->block_set); - return 0; err_unfreeze: @@ -519,28 +515,25 @@ int luo_file_freeze(struct luo_file_set file_set, /* * luo_file_unfreeze - Unfreezes all files in a file_set and clear serialization - * @file_set: The file_set whose files are to be unfrozen. - * @file_set_ser: Serialized file_set. + * @file_set: The file_set whose files are to be unfrozen. * * This function rolls back the state of all files in a file_set after the - * freeze phase has begun but must be aborted. It is the counterpart to - * luo_file_freeze(). + * freeze phase has begun. It is the counterpart to luo_file_freeze(). * * It invokes the __luo_file_unfreeze() helper with a NULL argument, which - * signals the helper to iterate through all files in the file_set and call - * their respective .unfreeze() handler callbacks. + * signals the helper to iterate through all files in the file_set, call their + * respective .unfreeze() handler callbacks, and clear the serialized blocks. * * Context: This is called when the live update is aborted during - * the reboot() syscall, after luo_file_freeze() has been called. + * the reboot() syscall, after luo_file_freeze() has been called, + * or when an explicitly frozen session is released before kexec. / -void luo_file_unfreeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser) +void luo_file_unfreeze(struct luo_file_set file_set) { if (!file_set->count) return; __luo_file_unfreeze(file_set, NULL); - memset(file_set_ser, 0, sizeof(file_set_ser)); } /* diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h index dac6644bfb18a..381499e73d2ac 100644 --- a/kernel/liveupdate/luo_internal.h +++ b/kernel/liveupdate/luo_internal.h @@ -64,6 +64,8 @@ struct luo_file_set { * previous kernel) sessions. * @retrieved: A boolean flag indicating whether this session has been * retrieved by a consumer in the new kernel. + * @user_frozen: A boolean flag indicating whether this session has been + * frozen explicitly from userspace. * @file_set: A set of files that belong to this session. * @mutex: protects fields in the luo_session. / @@ -71,6 +73,7 @@ struct luo_session { char name[LIVEUPDATE_SESSION_NAME_LENGTH]; struct list_head list; bool retrieved; + bool user_frozen; struct luo_file_set file_set; struct mutex mutex; }; @@ -103,10 +106,8 @@ int luo_session_deserialize(void); int luo_preserve_file(struct luo_file_set file_set, u64 token, int fd); void luo_file_unpreserve_files(struct luo_file_set file_set); -int luo_file_freeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser); -void luo_file_unfreeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser); +int luo_file_freeze(struct luo_file_set file_set); +void luo_file_unfreeze(struct luo_file_set file_set); int luo_retrieve_file(struct luo_file_set file_set, u64 token, struct file *filep); int luo_file_finish(struct luo_file_set file_set); diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c index f48e9a4185f97..cce6d09280b3e 100644 --- a/kernel/liveupdate/luo_session.c +++ b/kernel/liveupdate/luo_session.c @@ -34,10 +34,11 @@ * 1. Creation: A userspace agent calls `luo_session_create()` to create a * new, empty session and receives a file descriptor for it. * - * 2. Serialization: When the `reboot(LINUX_REBOOT_CMD_KEXEC)` syscall is - * made, `luo_session_serialize()` is called. It iterates through all - * active sessions and writes their metadata into a memory area preserved - * by KHO. + * 2. Freeze / Serialization: Sessions may be frozen explicitly from userspace + * via `LIVEUPDATE_SESSION_FREEZE`. When the `reboot(LINUX_REBOOT_CMD_KEXEC)` + * syscall is made, `luo_session_serialize()` is called to freeze any + * remaining active sessions and write all session metadata into a memory + * area preserved by KHO. * * 3. Deserialization (in new kernel): After kexec, `luo_session_deserialize()` * runs, reading the serialized data and creating a list of `struct @@ -218,18 +219,38 @@ static int luo_session_finish_one(struct luo_session session) return luo_file_finish(&session->file_set); } -static void luo_session_unfreeze_one(struct luo_session session, - struct luo_session_ser ser) +static void luo_session_unserialize_one(struct luo_session session, + struct luo_session_ser ser) { guard(mutex)(&session->mutex); - luo_file_unfreeze(&session->file_set, &ser->file_set_ser); + / + * Only unfreeze sessions that were auto-frozen by + * luo_session_serialize_one(); sessions frozen explicitly by + * userspace stay frozen until the session FD is closed. + / + if (!session->user_frozen) + luo_file_unfreeze(&session->file_set); + memset(ser, 0, sizeof(ser)); } -static int luo_session_freeze_one(struct luo_session session, - struct luo_session_ser ser) +static int luo_session_serialize_one(struct luo_session session, + struct luo_session_ser ser) { + int err; + guard(mutex)(&session->mutex); - return luo_file_freeze(&session->file_set, &ser->file_set_ser); + if (!session->user_frozen) { + err = luo_file_freeze(&session->file_set); + if (err) + return err; + } + + strscpy(ser->name, session->name, sizeof(ser->name)); + ser->file_set_ser.count = session->file_set.count; + ser->file_set_ser.files = + kho_block_set_head_pa(&session->file_set.block_set); + + return 0; } static int luo_session_release(struct inode inodep, struct file filep) @@ -249,8 +270,11 @@ static int luo_session_release(struct inode inodep, struct file filep) } sh = &luo_session_global.incoming; } else { - scoped_guard(mutex, &session->mutex) + scoped_guard(mutex, &session->mutex) { + if (session->user_frozen) + luo_file_unfreeze(&session->file_set); luo_file_unpreserve_files(&session->file_set); + } sh = &luo_session_global.outgoing; } @@ -267,6 +291,9 @@ static int luo_session_preserve_fd(struct luo_session session, int err; guard(mutex)(&session->mutex); + if (session->user_frozen) + return -EBUSY; + err = luo_preserve_file(&session->file_set, argp->token, argp->fd); if (err) return err; @@ -340,11 +367,40 @@ static int luo_session_get_name(struct luo_session session, return luo_ucmd_respond(ucmd, sizeof(argp)); } +static int luo_session_freeze(struct luo_session session, + struct luo_ucmd ucmd) +{ + struct liveupdate_session_freeze argp = ucmd->cmd; + int err; + + if (argp->reserved) + return -EINVAL; + + guard(mutex)(&session->mutex); + if (session->user_frozen) + return -EBUSY; + + err = luo_file_freeze(&session->file_set); + if (err) + return err; + + err = luo_ucmd_respond(ucmd, sizeof(argp)); + if (err) { + luo_file_unfreeze(&session->file_set); + return err; + } + + session->user_frozen = true; + + return 0; +} + union ucmd_buffer { struct liveupdate_session_finish finish; struct liveupdate_session_preserve_fd preserve; struct liveupdate_session_retrieve_fd retrieve; struct liveupdate_session_get_name get_name; + struct liveupdate_session_freeze freeze; }; / Type of sessions the ioctl applies to. / @@ -382,6 +438,8 @@ static const struct luo_ioctl_op luo_session_ioctl_ops[] = { struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING), IOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name, struct liveupdate_session_get_name, name, LUO_IOCTL_ALL), + IOCTL_OP(LIVEUPDATE_SESSION_FREEZE, luo_session_freeze, + struct liveupdate_session_freeze, reserved, LUO_IOCTL_OUTGOING), }; static bool luo_ioctl_type_valid(struct luo_session session, @@ -656,13 +714,11 @@ int luo_session_serialize(void) goto err_undo; } - err = luo_session_freeze_one(session, ser); + err = luo_session_serialize_one(session, ser); if (err) { kho_block_set_it_prev(&it); goto err_undo; } - - strscpy(ser->name, session->name, sizeof(ser->name)); } if (sh->count > 0) @@ -675,8 +731,7 @@ int luo_session_serialize(void) list_for_each_entry_continue_reverse(session, &sh->list, list) { struct luo_session_ser ser = kho_block_set_it_prev(&it); - luo_session_unfreeze_one(session, ser); - memset(ser->name, 0, sizeof(ser->name)); + luo_session_unserialize_one(session, ser); } up_write(&sh->rwsem); up_write(&luo_session_serialize_rwsem); diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c index 6b68220275ebe..a3bf872b3a03f 100644 --- a/mm/memfd_luo.c +++ b/mm/memfd_luo.c @@ -43,8 +43,9 @@ allocating pages for them during preservation. * * File Position - * The current file position is preserved, allowing applications to continue - * reading/writing from their last position. + * The file position at the time the session is frozen is preserved, + * allowing applications to continue reading/writing from their last + * position. * * File Status Flags * memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property diff --git a/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h b/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h index fa07fed083646..15a7db3a6b3e8 100644 --- a/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h +++ b/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h @@ -26,6 +26,7 @@ int luo_create_session(int luo_fd, const char name); int luo_retrieve_session(int luo_fd, const char name); int luo_session_finish(int session_fd); int luo_get_session_name(int session_fd, char name, size_t name_len); +int luo_session_freeze(int session_fd); int luo_ensure_nofile_limit(long min_limit); int luo_session_preserve_fd(int session_fd, int fd, __u64 token); diff --git a/tools/testing/selftests/liveupdate/lib/lu_utils.c b/tools/testing/selftests/liveupdate/lib/lu_utils.c index 74d41115c2815..6315746ff08f8 100644 --- a/tools/testing/selftests/liveupdate/lib/lu_utils.c +++ b/tools/testing/selftests/liveupdate/lib/lu_utils.c @@ -198,6 +198,16 @@ int luo_session_finish(int session_fd) return 0; } +int luo_session_freeze(int session_fd) +{ + struct liveupdate_session_freeze arg = { .size = sizeof(arg) }; + + if (ioctl(session_fd, LIVEUPDATE_SESSION_FREEZE, &arg) < 0) + return -errno; + + return 0; +} + void create_state_file(int luo_fd, const char session_name, int token, int next_stage) { diff --git a/tools/testing/selftests/liveupdate/liveupdate.c b/tools/testing/selftests/liveupdate/liveupdate.c index 2dedd5fc2534f..c27f57eab8707 100644 --- a/tools/testing/selftests/liveupdate/liveupdate.c +++ b/tools/testing/selftests/liveupdate/liveupdate.c @@ -530,4 +530,49 @@ TEST_F(liveupdate_device, preserve_many_files) ASSERT_EQ(close(session_fd), 0); } +/* + * Test Case: Session Freeze + * + * Verifies the LIVEUPDATE_SESSION_FREEZE ioctl on an outgoing session. + / +TEST_F(liveupdate_device, session_freeze) +{ + struct liveupdate_session_freeze bad_arg = { + .size = sizeof(bad_arg), + .reserved = 1, + }; + int session_fd, mem_fd1, mem_fd2; + + self->fd1 = open(LIVEUPDATE_DEV, O_RDWR); + if (self->fd1 < 0 && errno == ENOENT) + SKIP(return, "%s does not exist", LIVEUPDATE_DEV); + ASSERT_GE(self->fd1, 0); + + session_fd = luo_create_session(self->fd1, "session-freeze-test"); + ASSERT_GE(session_fd, 0); + + mem_fd1 = memfd_create("freeze-memfd-1", 0); + ASSERT_GE(mem_fd1, 0); + ASSERT_EQ(luo_session_preserve_fd(session_fd, mem_fd1, 0x1111), 0); + + / Non-zero reserved field must fail with -EINVAL / + EXPECT_EQ(ioctl(session_fd, LIVEUPDATE_SESSION_FREEZE, &bad_arg), -1); + EXPECT_EQ(errno, EINVAL); + + / Freeze the session early / + ASSERT_EQ(luo_session_freeze(session_fd), 0); + + / Subsequent freeze attempt on an already frozen session must fail with -EBUSY / + EXPECT_EQ(luo_session_freeze(session_fd), -EBUSY); + + / Preserving a file after freeze must fail with -EBUSY */ + mem_fd2 = memfd_create("freeze-memfd-2", 0); + ASSERT_GE(mem_fd2, 0); + EXPECT_EQ(luo_session_preserve_fd(session_fd, mem_fd2, 0x2222), -EBUSY); + + ASSERT_EQ(close(session_fd), 0); + ASSERT_EQ(close(mem_fd1), 0); + ASSERT_EQ(close(mem_fd2), 0); +} + TEST_HARNESS_MAIN diff --git a/tools/testing/selftests/liveupdate/luo_kexec_simple.c b/tools/testing/selftests/liveupdate/luo_kexec_simple.c index 786ac93b9ae38..9bc8dab2e074c 100644 --- a/tools/testing/selftests/liveupdate/luo_kexec_simple.c +++ b/tools/testing/selftests/liveupdate/luo_kexec_simple.c @@ -40,6 +40,11 @@ static void run_stage_1(int luo_fd) TEST_MEMFD_TOKEN); } + ksft_print_msg("[STAGE 1] Freezing session '%s' early...\n", + TEST_SESSION_NAME); + if (luo_session_freeze(session_fd) < 0) + fail_exit("luo_session_freeze for '%s'", TEST_SESSION_NAME); + close(luo_fd); daemonize_and_wait(); } @@ -60,6 +65,9 @@ static void run_stage_2(int luo_fd, int state_session_fd) if (session_fd < 0) fail_exit("luo_retrieve_session for '%s'", TEST_SESSION_NAME); + if (luo_session_freeze(session_fd) != -EINVAL) + fail_exit("luo_session_freeze on incoming session did not return -EINVAL"); + ksft_print_msg("[STAGE 2] Restoring and verifying memfd (token %#x)...\n", TEST_MEMFD_TOKEN); mfd = restore_and_verify_memfd(session_fd, TEST_MEMFD_TOKEN,
3/2	2026/10/26 02:25	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10505 output: 36 thoughts: 107 Thoughts: Analyzing the Liveupdate Kernel Patch Okay, so this patch introduces `LIVEUPDATE_SESSION_FREEZE` within the `liveupdate` subsystem. It seems like a significant change, touching several files: `luo_session.c`, `luo_file.c`, and both the user-space and kernel-space header files: `liveupdate.h`. I need to understand the implications of this new `ioctl` and its impact on the existing live update mechanism. My initial thought is to dive straight into the relevant code. I need to get a clear picture of how this freeze functionality will integrate, and more importantly, what it means for the overall live update process. A quick review of the surrounding `liveupdate` code in `luo_session.c` and `luo_file.c` is definitely in order. I'll need to pay close attention to the existing state machines and any locking mechanisms to understand if the patch might introduce any concurrency issues or race conditions. Then, I'll need to figure out the Kconfig options that control the liveupdate subsystem. I need to ascertain if this is a conditionally compiled feature, and what the dependencies are, and that is going to need a quick search. Time to use `grepper` or perhaps `codesearch-dir-index` to locate the relevant Kconfig entries. This will provide insight into the build configurations that enable this new functionality. It's a critical step to understand how broadly this change will affect different kernel builds.
4/2	2026/10/26 02:25	tool	grepper	0m Args: { "Expression": "LIVEUPDATE", "PathPrefixes": [ "kernel/liveupdate", "drivers", "Kconfig" ] } Results: { "Output": "drivers/pci/Kconfig=266=config VGA_ARB_MAX_GPUS\n--\ndrivers/pci/Kconfig-273-\ndrivers/pci/Kconfig:274:config PCI_LIVEUPDATE\ndrivers/pci/Kconfig-275-\tbool \"PCI Live Update Support\"\ndrivers/pci/Kconfig:276:\tdepends on PCI \u0026\u0026 LIVEUPDATE \u0026\u0026 64BIT \u0026\u0026 !CARDBUS\ndrivers/pci/Kconfig-277-\thelp\n--\ndrivers/pci/Makefile=18=obj-$(CONFIG_GENERIC_PCI_IOMAP) += iomap.o\ndrivers/pci/Makefile:19:obj-$(CONFIG_PCI_LIVEUPDATE)\t+= liveupdate.o\ndrivers/pci/Makefile-20-endif\n--\ndrivers/pci/liveupdate.c-25- * and userspace preserves the device with\ndrivers/pci/liveupdate.c:26: * ``ioctl(LIVEUPDATE_SESSION_PRESERVE_FD)`` on that file. Binding preservation\ndrivers/pci/liveupdate.c-27- * to a file gives it proper lifecycle management, e.g. the preservation is\n--\ndrivers/pci/liveupdate.c-60- \ndrivers/pci/liveupdate.c:61: # Userspace: ioctl(LIVEUPDATE_SESSION_PRESERVE_FD, devfd)\ndrivers/pci/liveupdate.c-62- * luo_preserve_file()\n--\ndrivers/pci/liveupdate.c-83- \ndrivers/pci/liveupdate.c:84: # Userspace: ioctl(LIVEUPDATE_SESSION_FINISH)\ndrivers/pci/liveupdate.c-85- * luo_file_finish_one()\n--\ndrivers/pci/liveupdate.h-7- /\ndrivers/pci/liveupdate.h:8:#ifndef DRIVERS_PCI_LIVEUPDATE_H\ndrivers/pci/liveupdate.h:9:#define DRIVERS_PCI_LIVEUPDATE_H\ndrivers/pci/liveupdate.h-10-\n--\ndrivers/pci/liveupdate.h-12-\ndrivers/pci/liveupdate.h:13:#ifdef CONFIG_PCI_LIVEUPDATE\ndrivers/pci/liveupdate.h-14-void pci_liveupdate_setup_device(struct pci_dev dev);\n--\ndrivers/pci/liveupdate.h=56=static inline bool pci_liveupdate_is_outgoing(struct pci_dev dev)\n--\ndrivers/pci/liveupdate.h-61-\ndrivers/pci/liveupdate.h:62:#endif / DRIVERS_PCI_LIVEUPDATE_H /\n--\nkernel/liveupdate/Kconfig=37=config KEXEC_HANDOVER_ENABLE_DEFAULT\n--\nkernel/liveupdate/Kconfig-50-\nkernel/liveupdate/Kconfig:51:config LIVEUPDATE\nkernel/liveupdate/Kconfig-52-\tbool \"Live Update Orchestrator\"\n--\nkernel/liveupdate/Kconfig-71-\nkernel/liveupdate/Kconfig:72:config LIVEUPDATE_MEMFD\nkernel/liveupdate/Kconfig-73-\tbool \"Live update support for memfd\"\nkernel/liveupdate/Kconfig:74:\tdepends on LIVEUPDATE\nkernel/liveupdate/Kconfig-75-\tdepends on MEMFD_CREATE\nkernel/liveupdate/Kconfig-76-\tdepends on SHMEM\nkernel/liveupdate/Kconfig:77:\tdefault LIVEUPDATE\nkernel/liveupdate/Kconfig-78-\thelp\n--\nkernel/liveupdate/Makefile=11=obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS)\t+= kexec_handover_debugfs.o\nkernel/liveupdate/Makefile-12-\nkernel/liveupdate/Makefile:13:obj-$(CONFIG_LIVEUPDATE)\t\t+= luo.o\n--\nkernel/liveupdate/luo_core.c=363=struct luo_ioctl_op {\n--\nkernel/liveupdate/luo_core.c-370-#define IOCTL_OP(_ioctl, _fn, _struct, _last) \\\nkernel/liveupdate/luo_core.c:371:\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_BASE] = { \\\nkernel/liveupdate/luo_core.c-372-\t\t.size = sizeof(_struct) + \\\n--\nkernel/liveupdate/luo_core.c=380=static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c:381:\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\nkernel/liveupdate/luo_core.c-382-\t\t struct liveupdate_ioctl_create_session, name),\nkernel/liveupdate/luo_core.c:383:\tIOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,\nkernel/liveupdate/luo_core.c-384-\t\t struct liveupdate_ioctl_retrieve_session, name),\n--\nkernel/liveupdate/luo_core.c=387=static long luo_ioctl(struct file filep, unsigned int cmd, unsigned long arg)\n--\nkernel/liveupdate/luo_core.c-395-\tnr = _IOC_NR(cmd);\nkernel/liveupdate/luo_core.c:396:\tif (nr - LIVEUPDATE_CMD_BASE \u003e= ARRAY_SIZE(luo_ioctl_ops))\nkernel/liveupdate/luo_core.c-397-\t\treturn -EINVAL;\n--\nkernel/liveupdate/luo_core.c-403-\nkernel/liveupdate/luo_core.c:404:\top = \u0026luo_ioctl_ops[nr - LIVEUPDATE_CMD_BASE];\nkernel/liveupdate/luo_core.c-405-\tif (op-\u003eioctl_num != cmd)\n--\nkernel/liveupdate/luo_file.c-34- * - freeze(): Prepares the final state for kexec. Invoked either via\nkernel/liveupdate/luo_file.c:35: * the LIVEUPDATE_SESSION_FREEZE ioctl once userspace is done modifying\nkernel/liveupdate/luo_file.c-36- * the session's files, or during the reboot() syscall.\n--\nkernel/liveupdate/luo_file.c-50- \nkernel/liveupdate/luo_file.c:51: 2. Freeze (Pre-Reboot): Either explicitly via LIVEUPDATE_SESSION_FREEZE or\nkernel/liveupdate/luo_file.c-52- * just before the kexec during reboot(), luo_file_freeze() is called.\n--\nkernel/liveupdate/luo_file.c-83- \nkernel/liveupdate/luo_file.c:84: 2. Freeze Failure: During LIVEUPDATE_SESSION_FREEZE or the reboot() syscall,\nkernel/liveupdate/luo_file.c-85- * if any handler's .freeze() op fails, the .unfreeze() op is invoked on all\n--\nkernel/liveupdate/luo_file.c=427=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-446- \nkernel/liveupdate/luo_file.c:447: * This function is called from LIVEUPDATE_SESSION_FREEZE or from the reboot()\nkernel/liveupdate/luo_file.c-448- * syscall path. Its purpose is to perform the final preparation and\n--\nkernel/liveupdate/luo_file.c-470- \nkernel/liveupdate/luo_file.c:471: Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path.\nkernel/liveupdate/luo_file.c-472- * Return: 0 on success, or a negative errno on failure.\n--\nkernel/liveupdate/luo_internal.h=72=struct luo_session {\nkernel/liveupdate/luo_internal.h:73:\tchar name[LIVEUPDATE_SESSION_NAME_LENGTH];\nkernel/liveupdate/luo_internal.h-74-\tstruct list_head list;\n--\nkernel/liveupdate/luo_internal.h=125=void luo_flb_serialize(void);\nkernel/liveupdate/luo_internal.h-126-\nkernel/liveupdate/luo_internal.h:127:#ifdef CONFIG_LIVEUPDATE_TEST\nkernel/liveupdate/luo_internal.h-128-void liveupdate_test_register(struct liveupdate_file_handler fh);\n--\nkernel/liveupdate/luo_session.c-37- 2. Freeze / Serialization: Sessions may be frozen explicitly from userspace\nkernel/liveupdate/luo_session.c:38: * via `LIVEUPDATE_SESSION_FREEZE`. When the `reboot(LINUX_REBOOT_CMD_KEXEC)`\nkernel/liveupdate/luo_session.c-39- * syscall is made, `luo_session_serialize()` is called to freeze any\n--\nkernel/liveupdate/luo_session.c=413=struct luo_ioctl_op {\n--\nkernel/liveupdate/luo_session.c-421-#define IOCTL_OP(_ioctl, _fn, _struct, _last, _type) \\\nkernel/liveupdate/luo_session.c:422:\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_SESSION_BASE] = { \\\nkernel/liveupdate/luo_session.c-423-\t\t.size = sizeof(_struct) + \\\n--\nkernel/liveupdate/luo_session.c=432=static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\nkernel/liveupdate/luo_session.c:433:\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\nkernel/liveupdate/luo_session.c-434-\t\t struct liveupdate_session_finish, reserved, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:435:\tIOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,\nkernel/liveupdate/luo_session.c-436-\t\t struct liveupdate_session_preserve_fd, token, LUO_IOCTL_OUTGOING),\nkernel/liveupdate/luo_session.c:437:\tIOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,\nkernel/liveupdate/luo_session.c-438-\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:439:\tIOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,\nkernel/liveupdate/luo_session.c-440-\t\t struct liveupdate_session_get_name, name, LUO_IOCTL_ALL),\nkernel/liveupdate/luo_session.c:441:\tIOCTL_OP(LIVEUPDATE_SESSION_FREEZE, luo_session_freeze,\nkernel/liveupdate/luo_session.c-442-\t\t struct liveupdate_session_freeze, reserved, LUO_IOCTL_OUTGOING),\n--\nkernel/liveupdate/luo_session.c=462=static long luo_session_ioctl(struct file filep, unsigned int cmd,\n--\nkernel/liveupdate/luo_session.c-472-\tnr = _IOC_NR(cmd);\nkernel/liveupdate/luo_session.c:473:\tif (nr \u003c LIVEUPDATE_CMD_SESSION_BASE \|\| (nr - LIVEUPDATE_CMD_SESSION_BASE) \u003e=\nkernel/liveupdate/luo_session.c-474-\t ARRAY_SIZE(luo_session_ioctl_ops)) {\n--\nkernel/liveupdate/luo_session.c-482-\nkernel/liveupdate/luo_session.c:483:\top = \u0026luo_session_ioctl_ops[nr - LIVEUPDATE_CMD_SESSION_BASE];\nkernel/liveupdate/luo_session.c-484-\tif (op-\u003eioctl_num != cmd)\n--\nkernel/liveupdate/luo_session.c=524=int luo_session_create(const char name, struct file *filep)\nkernel/liveupdate/luo_session.c-525-{\nkernel/liveupdate/luo_session.c:526:\tsize_t len = strnlen(name, LIVEUPDATE_SESSION_NAME_LENGTH);\nkernel/liveupdate/luo_session.c-527-\tstruct luo_session session;\n--\nkernel/liveupdate/luo_session.c-529-\nkernel/liveupdate/luo_session.c:530:\tif (len == 0 \|\| len \u003e LIVEUPDATE_SESSION_NAME_LENGTH - 1)\nkernel/liveupdate/luo_session.c-531-\t\treturn -EINVAL;\n" }
5/2	2026/10/26 02:25	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14253 output: 33 thoughts: 23 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Diving into Kernel Live Update Configuration Right, let's get down to brass tacks. I'm going to dig into the `kernel/liveupdate/Kconfig` file. I need to understand the dependencies and the entire enabling mechanism for the `LIVEUPDATE` functionality. It's crucial to grasp the configuration hierarchy. I'm thinking I'll be looking for relevant `depends on` statements, any conditional definitions, and any relationships to other kernel features. My goal here is to get a solid grasp of how it all hangs together from a configuration perspective. I want to see precisely what triggers the inclusion of `LIVEUPDATE` and what assumptions the build system makes when it's enabled. That'll inform my understanding of how to control, debug, or extend it later.
6/2	2026/10/26 02:26	tool	read-file	0m Args: { "File": "kernel/liveupdate/Kconfig", "FirstLine": 1, "LineCount": 85 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\t\n 3:\tmenu \"Live Update and Kexec HandOver\"\n 4:\t\n 5:\tconfig KEXEC_HANDOVER\n 6:\t\tbool \"kexec handover\"\n 7:\t\tdepends on ARCH_SUPPORTS_KEXEC_HANDOVER \u0026\u0026 ARCH_SUPPORTS_KEXEC_FILE\n 8:\t\tselect KEXEC_FILE\n 9:\t\tselect LIBFDT\n 10:\t\tselect CMA\n 11:\t\thelp\n 12:\t\t Allow kexec to hand over state across kernels by generating and\n 13:\t\t passing additional metadata to the target kernel. This is useful\n 14:\t\t to keep data or state alive across the kexec. For this to work,\n 15:\t\t both source and target kernels need to have this option enabled.\n 16:\t\n 17:\tconfig KEXEC_HANDOVER_DEBUG\n 18:\t\tbool \"Enable Kexec Handover debug checks\"\n 19:\t\tdepends on KEXEC_HANDOVER\n 20:\t\thelp\n 21:\t\t This option enables extra sanity checks for the Kexec Handover\n 22:\t\t subsystem. Since, KHO performance is crucial in live update\n 23:\t\t scenarios and the extra code might be adding overhead it is\n 24:\t\t only optionally enabled.\n 25:\t\n 26:\tconfig KEXEC_HANDOVER_DEBUGFS\n 27:\t\tbool \"kexec handover debugfs interface\"\n 28:\t\tdefault KEXEC_HANDOVER\n 29:\t\tdepends on KEXEC_HANDOVER\n 30:\t\tselect DEBUG_FS\n 31:\t\thelp\n 32:\t\t Allow to control kexec handover device tree via debugfs\n 33:\t\t interface, i.e. finalize the state or aborting the finalization.\n 34:\t\t Also, enables inspecting the KHO fdt trees with the debugfs binary\n 35:\t\t blobs.\n 36:\t\n 37:\tconfig KEXEC_HANDOVER_ENABLE_DEFAULT\n 38:\t\tbool \"Enable kexec handover by default\"\n 39:\t\tdepends on KEXEC_HANDOVER\n 40:\t\thelp\n 41:\t\t Enable Kexec Handover by default. This avoids the need to\n 42:\t\t explicitly pass 'kho=on' on the kernel command line.\n 43:\t\n 44:\t\t This is useful for systems where KHO is a prerequisite for other\n 45:\t\t features, such as Live Update, ensuring the mechanism is always\n 46:\t\t active.\n 47:\t\n 48:\t\t The default behavior can still be overridden at boot time by\n 49:\t\t passing 'kho=off'.\n 50:\t\n 51:\tconfig LIVEUPDATE\n 52:\t\tbool \"Live Update Orchestrator\"\n 53:\t\tdepends on KEXEC_HANDOVER\n 54:\t\thelp\n 55:\t\t Enable the Live Update Orchestrator. Live Update is a mechanism,\n 56:\t\t typically based on kexec, that allows the kernel to be updated\n 57:\t\t while keeping selected devices operational across the transition.\n 58:\t\t These devices are intended to be reclaimed by the new kernel and\n 59:\t\t re-attached to their original workload without requiring a device\n 60:\t\t reset.\n 61:\t\n 62:\t\t Ability to handover a device from current to the next kernel depends\n 63:\t\t on specific support within device drivers and related kernel\n 64:\t\t subsystems.\n 65:\t\n 66:\t\t This feature primarily targets virtual machine hosts to quickly update\n 67:\t\t the kernel hypervisor with minimal disruption to the running virtual\n 68:\t\t machines.\n 69:\t\n 70:\t\t If unsure, say N.\n 71:\t\n 72:\tconfig LIVEUPDATE_MEMFD\n 73:\t\tbool \"Live update support for memfd\"\n 74:\t\tdepends on LIVEUPDATE\n 75:\t\tdepends on MEMFD_CREATE\n 76:\t\tdepends on SHMEM\n 77:\t\tdefault LIVEUPDATE\n 78:\t\thelp\n 79:\t\t Enable live update support for memfd regions. This allows preserving\n 80:\t\t memfd-backed memory across kernel live updates.\n 81:\t\n 82:\t\t This can be used to back VM memory with memfds, allowing the guest\n 83:\t\t memory to persist, or for other user workloads needing to preserve\n 84:\t\t pages.\n 85:\t\n" }
7/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15626 output: 36 thoughts: 50 Thoughts: Here's my thought process, summarized as you requested: Investigating the Liveupdate Device Alright, let's dive into this liveupdate system. My initial instinct is to get a solid grasp on the fundamentals. I want to understand precisely how this liveupdate device is instantiated within the kernel. Specifically, I need to know: how is it created in the first place, what's the actual device node that's ultimately made available, and, crucially, how do userspace processes, and presumably our tools, interact with it? To start, I'll go straight to the source. The `kernel/liveupdate` directory is the logical place to start digging. My next step? Grep. I'll search for the `LIVEUPDATE_DEV` macro, if it's used, but I'll broaden the search to include "miscdevice" as well, since it's a common pattern for exposing character devices. This should give me a pretty clear picture of the device's setup. From there, I can trace the code and see how it is used.
8/2	2026/10/26 02:26	tool	grepper	0m Args: { "Expression": "misc_register\|LIVEUPDATE_DEV\|liveupdate", "PathPrefixes": [ "kernel/liveupdate" ] } Results: { "Output": "\nFull output is too long, showing 200 out of 521 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (5 files in total):\nkernel/liveupdate/luo_core.c:34\nkernel/liveupdate/luo_file.c:36\nkernel/liveupdate/luo_flb.c:42\nkernel/liveupdate/luo_internal.h:10\nkernel/liveupdate/luo_session.c:18\n\nkernel/liveupdate/luo_core.c-40- * .. note::\nkernel/liveupdate/luo_core.c:41: * To enable LUO, boot the kernel with the ``liveupdate=on`` command line\nkernel/liveupdate/luo_core.c-42- * parameter.\n--\nkernel/liveupdate/luo_core.c-56-#include \u003clinux/kobject.h\u003e\nkernel/liveupdate/luo_core.c:57:#include \u003clinux/liveupdate.h\u003e\nkernel/liveupdate/luo_core.c-58-#include \u003clinux/miscdevice.h\u003e\n--\nkernel/liveupdate/luo_core.c=67=static struct {\n--\nkernel/liveupdate/luo_core.c-69-\tstruct luo_ser luo_ser_out;\nkernel/liveupdate/luo_core.c:70:\tu64 liveupdate_num;\nkernel/liveupdate/luo_core.c-71-} luo_global;\n--\nkernel/liveupdate/luo_core.c=76=DECLARE_RWSEM(luo_register_rwlock);\nkernel/liveupdate/luo_core.c-77-\nkernel/liveupdate/luo_core.c:78:static int __init early_liveupdate_param(char buf)\nkernel/liveupdate/luo_core.c-79-{\n--\nkernel/liveupdate/luo_core.c-81-}\nkernel/liveupdate/luo_core.c:82:early_param(\"liveupdate\", early_liveupdate_param);\nkernel/liveupdate/luo_core.c-83-\nkernel/liveupdate/luo_core.c=84=static int __init luo_early_startup(void)\n--\nkernel/liveupdate/luo_core.c-91-\tif (!kho_is_enabled()) {\nkernel/liveupdate/luo_core.c:92:\t\tif (liveupdate_enabled())\nkernel/liveupdate/luo_core.c:93:\t\t\tpr_warn(\"Disabling liveupdate because KHO is disabled\\n\");\nkernel/liveupdate/luo_core.c-94-\t\tluo_global.enabled = false;\n--\nkernel/liveupdate/luo_core.c-120-\nkernel/liveupdate/luo_core.c:121:\tluo_global.liveupdate_num = luo_ser-\u003eliveupdate_num;\nkernel/liveupdate/luo_core.c:122:\tpr_info(\"Retrieved live update data, liveupdate number: %lld\\n\",\nkernel/liveupdate/luo_core.c:123:\t\tluo_global.liveupdate_num);\nkernel/liveupdate/luo_core.c-124-\n--\nkernel/liveupdate/luo_core.c-137-\nkernel/liveupdate/luo_core.c:138:static int __init liveupdate_early_init(void)\nkernel/liveupdate/luo_core.c-139-{\n--\nkernel/liveupdate/luo_core.c-150-}\nkernel/liveupdate/luo_core.c:151:early_initcall(liveupdate_early_init);\nkernel/liveupdate/luo_core.c-152-\n--\nkernel/liveupdate/luo_core.c=154=static int __init luo_state_setup(void)\n--\nkernel/liveupdate/luo_core.c-165-\tstrscpy(luo_ser-\u003ecompatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser-\u003ecompatible));\nkernel/liveupdate/luo_core.c:166:\tluo_ser-\u003eliveupdate_num = luo_global.liveupdate_num + 1;\nkernel/liveupdate/luo_core.c-167-\n--\nkernel/liveupdate/luo_core.c-190- * late initcall because it initializes the outgoing tree that is needed only\nkernel/liveupdate/luo_core.c:191: * once userspace starts using /dev/liveupdate.\nkernel/liveupdate/luo_core.c-192- /\nkernel/liveupdate/luo_core.c=193=static int __init luo_late_startup(void)\n--\nkernel/liveupdate/luo_core.c-196-\nkernel/liveupdate/luo_core.c:197:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-198-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c=206=late_initcall(luo_late_startup);\n--\nkernel/liveupdate/luo_core.c-210-/\nkernel/liveupdate/luo_core.c:211: liveupdate_reboot() - Kernel reboot notifier for live update final\nkernel/liveupdate/luo_core.c-212- * serialization.\n--\nkernel/liveupdate/luo_core.c-219- /\nkernel/liveupdate/luo_core.c:220:int liveupdate_reboot(void)\nkernel/liveupdate/luo_core.c-221-{\n--\nkernel/liveupdate/luo_core.c-223-\nkernel/liveupdate/luo_core.c:224:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-225-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c-236-/\nkernel/liveupdate/luo_core.c:237: liveupdate_enabled - Check if the live update feature is enabled.\nkernel/liveupdate/luo_core.c-238- \nkernel/liveupdate/luo_core.c-239- This function returns the state of the live update feature flag, which\nkernel/liveupdate/luo_core.c:240: * can be controlled via the ``liveupdate`` kernel command-line parameter.\nkernel/liveupdate/luo_core.c-241- \n--\nkernel/liveupdate/luo_core.c-243- /\nkernel/liveupdate/luo_core.c:244:bool liveupdate_enabled(void)\nkernel/liveupdate/luo_core.c-245-{\n--\nkernel/liveupdate/luo_core.c-252- * The IOCTL user-space control interface for the LUO subsystem.\nkernel/liveupdate/luo_core.c:253: * It registers a character device, typically found at ``/dev/liveupdate``,\nkernel/liveupdate/luo_core.c-254- * which allows a userspace agent to manage the LUO state machine and its\n--\nkernel/liveupdate/luo_core.c-258- * to this device is exclusive: only one process is permitted to have\nkernel/liveupdate/luo_core.c:259: * ``/dev/liveupdate`` open at any given time. Subsequent open attempts will\nkernel/liveupdate/luo_core.c-260- * fail with -EBUSY until the first process closes its file descriptor.\n--\nkernel/liveupdate/luo_core.c=270=static int luo_ioctl_create_session(struct luo_ucmd ucmd)\nkernel/liveupdate/luo_core.c-271-{\nkernel/liveupdate/luo_core.c:272:\tstruct liveupdate_ioctl_create_session argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-273-\tstruct file file;\n--\nkernel/liveupdate/luo_core.c=300=static int luo_ioctl_retrieve_session(struct luo_ucmd ucmd)\nkernel/liveupdate/luo_core.c-301-{\nkernel/liveupdate/luo_core.c:302:\tstruct liveupdate_ioctl_retrieve_session argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-303-\tstruct file file;\n--\nkernel/liveupdate/luo_core.c=358=union ucmd_buffer {\nkernel/liveupdate/luo_core.c:359:\tstruct liveupdate_ioctl_create_session create;\nkernel/liveupdate/luo_core.c:360:\tstruct liveupdate_ioctl_retrieve_session retrieve;\nkernel/liveupdate/luo_core.c-361-};\n--\nkernel/liveupdate/luo_core.c=380=static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c-381-\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\nkernel/liveupdate/luo_core.c:382:\t\t struct liveupdate_ioctl_create_session, name),\nkernel/liveupdate/luo_core.c-383-\tIOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,\nkernel/liveupdate/luo_core.c:384:\t\t struct liveupdate_ioctl_retrieve_session, name),\nkernel/liveupdate/luo_core.c-385-};\n--\nkernel/liveupdate/luo_core.c=426=static struct luo_device_state luo_dev = {\n--\nkernel/liveupdate/luo_core.c-428-\t\t.minor = MISC_DYNAMIC_MINOR,\nkernel/liveupdate/luo_core.c:429:\t\t.name = \"liveupdate\",\nkernel/liveupdate/luo_core.c-430-\t\t.fops = \u0026luo_fops,\n--\nkernel/liveupdate/luo_core.c-434-\nkernel/liveupdate/luo_core.c:435:static int __init liveupdate_ioctl_init(void)\nkernel/liveupdate/luo_core.c-436-{\nkernel/liveupdate/luo_core.c:437:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-438-\t\treturn 0;\nkernel/liveupdate/luo_core.c-439-\nkernel/liveupdate/luo_core.c:440:\treturn misc_register(\u0026luo_dev.miscdev);\nkernel/liveupdate/luo_core.c-441-}\nkernel/liveupdate/luo_core.c:442:late_initcall(liveupdate_ioctl_init);\n--\nkernel/liveupdate/luo_file.c-20- * Kernel modules responsible for a specific file type (e.g., memfd, vfio)\nkernel/liveupdate/luo_file.c:21: * register a \u0026struct liveupdate_file_handler. This handler provides a set of\nkernel/liveupdate/luo_file.c-22- * callbacks that LUO invokes at different stages of the update process, most\n--\nkernel/liveupdate/luo_file.c-57- * 3. Deserialize: After kexec, luo_file_deserialize() runs when session gets\nkernel/liveupdate/luo_file.c:58: * deserialized (which is when /dev/liveupdate is first opened). It reads the\nkernel/liveupdate/luo_file.c-59- * serialized data from the KHO memory region and reconstructs the in-memory\n--\nkernel/liveupdate/luo_file.c-124-#include \u003clinux/list_private.h\u003e\nkernel/liveupdate/luo_file.c:125:#include \u003clinux/liveupdate.h\u003e\nkernel/liveupdate/luo_file.c-126-#include \u003clinux/module.h\u003e\n--\nkernel/liveupdate/luo_file.c=136=static DEFINE_XARRAY(luo_preserved_files);\n--\nkernel/liveupdate/luo_file.c-139- * struct luo_file - Represents a single preserved file instance.\nkernel/liveupdate/luo_file.c:140: * @fh: Pointer to the \u0026struct liveupdate_file_handler that manages\nkernel/liveupdate/luo_file.c-141- * this type of file.\n--\nkernel/liveupdate/luo_file.c=178=struct luo_file {\nkernel/liveupdate/luo_file.c:179:\tstruct liveupdate_file_handler fh;\nkernel/liveupdate/luo_file.c-180-\tstruct file file;\n--\nkernel/liveupdate/luo_file.c-188-\nkernel/liveupdate/luo_file.c:189:static unsigned long luo_get_id(struct liveupdate_file_handler fh,\nkernel/liveupdate/luo_file.c-190-\t\t\t\tstruct file file)\n--\nkernel/liveupdate/luo_file.c=247=int luo_preserve_file(struct luo_file_set file_set, u64 token, int fd)\nkernel/liveupdate/luo_file.c-248-{\nkernel/liveupdate/luo_file.c:249:\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c:250:\tstruct liveupdate_file_handler fh;\nkernel/liveupdate/luo_file.c-251-\tstruct luo_file luo_file;\n--\nkernel/liveupdate/luo_file.c=351=void luo_file_unpreserve_files(struct luo_file_set file_set)\n--\nkernel/liveupdate/luo_file.c-355-\twhile (!list_empty(\u0026file_set-\u003efiles_list)) {\nkernel/liveupdate/luo_file.c:356:\t\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-357-\n--\nkernel/liveupdate/luo_file.c=385=static int luo_file_freeze_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-392-\tif (luo_file-\u003efh-\u003eops-\u003efreeze) {\nkernel/liveupdate/luo_file.c:393:\t\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-394-\n--\nkernel/liveupdate/luo_file.c=409=static void luo_file_unfreeze_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-414-\tif (luo_file-\u003efh-\u003eops-\u003eunfreeze) {\nkernel/liveupdate/luo_file.c:415:\t\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-416-\n--\nkernel/liveupdate/luo_file.c=427=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-470- \nkernel/liveupdate/luo_file.c:471: * Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path.\nkernel/liveupdate/luo_file.c-472- * Return: 0 on success, or a negative errno on failure.\n--\nkernel/liveupdate/luo_file.c=564=int luo_retrieve_file(struct luo_file_set file_set, u64 token,\n--\nkernel/liveupdate/luo_file.c-566-{\nkernel/liveupdate/luo_file.c:567:\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-568-\tstruct luo_file luo_file;\n--\nkernel/liveupdate/luo_file.c=625=static int luo_file_can_finish_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-632-\tif (luo_file-\u003efh-\u003eops-\u003ecan_finish) {\nkernel/liveupdate/luo_file.c:633:\t\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-634-\n--\nkernel/liveupdate/luo_file.c=646=static void luo_file_finish_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-648-{\n\n" }
9/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 20270 output: 39 thoughts: 31 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Diving into `luo_file_freeze_one` and Associated Code Right, let's get down to brass tacks. I need to take a fresh look at `luo_file_freeze_one` and the surrounding code in `kernel/liveupdate/luo_file.c`. My gut feeling is that this area is likely a choke point or potential source of issues within the live update process. I want to carefully examine its interaction with the file system, understand its locking semantics, and assess the potential for race conditions or deadlocks, especially under heavy I/O load during an update. I'll need to remember to check how it handles different error conditions too, and whether there are any vulnerabilities I may need to address. A close inspection will reveal how it interacts with the broader live update framework.
10/2	2026/10/26 02:26	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_file.c", "FirstLine": 380, "LineCount": 80 } Results: { "Contents": " 380:\t\t}\n 381:\t\n 382:\t\tkho_block_set_destroy(\u0026file_set-\u003eblock_set);\n 383:\t}\n 384:\t\n 385:\tstatic int luo_file_freeze_one(struct luo_file_set file_set,\n 386:\t\t\t\t struct luo_file luo_file)\n 387:\t{\n 388:\t\tint err = 0;\n 389:\t\n 390:\t\tguard(mutex)(\u0026luo_file-\u003emutex);\n 391:\t\n 392:\t\tif (luo_file-\u003efh-\u003eops-\u003efreeze) {\n 393:\t\t\tstruct liveupdate_file_op_args args = {0};\n 394:\t\n 395:\t\t\targs.handler = luo_file-\u003efh;\n 396:\t\t\targs.session = luo_session_from_file_set(file_set);\n 397:\t\t\targs.file = luo_file-\u003efile;\n 398:\t\t\targs.serialized_data = luo_file-\u003eserialized_data;\n 399:\t\t\targs.private_data = luo_file-\u003eprivate_data;\n 400:\t\n 401:\t\t\terr = luo_file-\u003efh-\u003eops-\u003efreeze(\u0026args);\n 402:\t\t\tif (!err)\n 403:\t\t\t\tluo_file-\u003eserialized_data = args.serialized_data;\n 404:\t\t}\n 405:\t\n 406:\t\treturn err;\n 407:\t}\n 408:\t\n 409:\tstatic void luo_file_unfreeze_one(struct luo_file_set file_set,\n 410:\t\t\t\t\t struct luo_file luo_file)\n 411:\t{\n 412:\t\tguard(mutex)(\u0026luo_file-\u003emutex);\n 413:\t\n 414:\t\tif (luo_file-\u003efh-\u003eops-\u003eunfreeze) {\n 415:\t\t\tstruct liveupdate_file_op_args args = {0};\n 416:\t\n 417:\t\t\targs.handler = luo_file-\u003efh;\n 418:\t\t\targs.session = luo_session_from_file_set(file_set);\n 419:\t\t\targs.file = luo_file-\u003efile;\n 420:\t\t\targs.serialized_data = luo_file-\u003eserialized_data;\n 421:\t\t\targs.private_data = luo_file-\u003eprivate_data;\n 422:\t\n 423:\t\t\tluo_file-\u003efh-\u003eops-\u003eunfreeze(\u0026args);\n 424:\t\t}\n 425:\t}\n 426:\t\n 427:\tstatic void __luo_file_unfreeze(struct luo_file_set file_set,\n 428:\t\t\t\t\tstruct luo_file failed_entry)\n 429:\t{\n 430:\t\tstruct list_head files_list = \u0026file_set-\u003efiles_list;\n 431:\t\tstruct luo_file luo_file;\n 432:\t\n 433:\t\tlist_for_each_entry(luo_file, files_list, list) {\n 434:\t\t\tif (luo_file == failed_entry)\n 435:\t\t\t\tbreak;\n 436:\t\n 437:\t\t\tluo_file_unfreeze_one(file_set, luo_file);\n 438:\t\t}\n 439:\t\n 440:\t\tkho_block_set_clear(\u0026file_set-\u003eblock_set);\n 441:\t}\n 442:\t\n 443:\t/*\n 444:\t luo_file_freeze - Freezes all preserved files and serializes their metadata.\n 445:\t * @file_set: The file_set whose files are to be frozen.\n 446:\t \n 447:\t This function is called from LIVEUPDATE_SESSION_FREEZE or from the reboot()\n 448:\t * syscall path. Its purpose is to perform the final preparation and\n 449:\t * serialization of all preserved files in the file_set.\n 450:\t \n 451:\t It iterates through each preserved file in FIFO order (the order of\n 452:\t * preservation) and performs two main actions:\n 453:\t \n 454:\t 1. Freezes the File: It calls the handler's .freeze() callback for each\n 455:\t * file. This gives the handler a final opportunity to quiesce the device or\n 456:\t * prepare its state for the upcoming reboot. The handler may update its\n 457:\t * private data handle during this step.\n 458:\t \n 459:\t 2. Serializes Metadata: After a successful freeze, it copies the final file\n" }
11/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21797 output: 29 thoughts: 47 Thoughts: Okay, let's dive into this code. Investigating the `liveupdate_file_handler` Registration My initial thought is to figure out what's registering that `liveupdate_file_handler`, especially how the `freeze` and `unfreeze` callbacks are handled within it. It's a critical point to understand how updates are managed. To get a handle on this, I'll go right into the codebase and run a `grep` command. I'll search for occurrences of either `.freeze` (since that’s a likely method name) or the full `liveupdate_file_handler` string. This should allow me to pinpoint the exact locations where this handler is being registered and where those crucial callbacks are defined and used. Understanding the registration process is the cornerstone of understanding how the whole update system operates.
12/2	2026/10/26 02:26	tool	grepper	0m Args: { "Expression": "liveupdate_file_handler\|liveupdate_register_file_handler" } Results: { "Output": "\nFull output is too long, showing 200 out of 219 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (8 files in total):\ndrivers/pci/liveupdate.c:7\ninclude/linux/liveupdate.h:13\ninclude/linux/pci_liveupdate.h:4\nkernel/liveupdate/luo_file.c:12\nkernel/liveupdate/luo_flb.c:7\nkernel/liveupdate/luo_internal.h:6\nlib/tests/liveupdate.c:1\nmm/memfd_luo.c:3\n\ndrivers/pci/liveupdate.c-33- * represents a PCI device. Drivers therefore register their\ndrivers/pci/liveupdate.c:34: * struct liveupdate_file_handler with the PCI core:\ndrivers/pci/liveupdate.c-35- \n--\ndrivers/pci/liveupdate.c=526=static int pci_liveupdate_preserve_device(struct pci_flb_outgoing outgoing,\n--\ndrivers/pci/liveupdate.c-589- * preserved across the next Live Update. Drivers are expected to call\ndrivers/pci/liveupdate.c:590: * pci_liveupdate_preserve() from their struct liveupdate_file_handler\ndrivers/pci/liveupdate.c-591- * preserve() callback to ensure the outgoing struct pci_ser is already set up.\n--\ndrivers/pci/liveupdate.c=621=EXPORT_SYMBOL_GPL(pci_liveupdate_preserve);\n--\ndrivers/pci/liveupdate.c-628- * longer be preserved across the next Live Update. Drivers are expected to call\ndrivers/pci/liveupdate.c:629: * pci_liveupdate_unpreserve() from their struct liveupdate_file_handler\ndrivers/pci/liveupdate.c-630- * unpreserve() callback to ensure the outgoing struct pci_ser is already set\n--\ndrivers/pci/liveupdate.c=820=static int pci_liveupdate_finish_device(struct pci_ser ser, struct pci_dev dev)\n--\ndrivers/pci/liveupdate.c-852- * Update. Drivers must call pci_liveupdate_finish() from their struct\ndrivers/pci/liveupdate.c:853: * liveupdate_file_handler finish() callback to ensure the incoming struct\ndrivers/pci/liveupdate.c-854- * pci_ser is allocated.\n--\ndrivers/pci/liveupdate.c=981=EXPORT_SYMBOL_GPL(pci_liveupdate_is_incoming);\n--\ndrivers/pci/liveupdate.c-988- * pci_liveupdate_register_flb() to register their\ndrivers/pci/liveupdate.c:989: * struct liveupdate_file_handler with the PCI core, typically at module init,\ndrivers/pci/liveupdate.c-990- * and always before any file managed by @fh can be preserved.\n--\ndrivers/pci/liveupdate.c-998- /\ndrivers/pci/liveupdate.c:999:int pci_liveupdate_register_flb(struct liveupdate_file_handler fh)\ndrivers/pci/liveupdate.c-1000-{\n--\ndrivers/pci/liveupdate.c=1004=EXPORT_SYMBOL_GPL(pci_liveupdate_register_flb);\n--\ndrivers/pci/liveupdate.c-1009- /\ndrivers/pci/liveupdate.c:1010:void pci_liveupdate_unregister_flb(struct liveupdate_file_handler fh)\ndrivers/pci/liveupdate.c-1011-{\n--\ninclude/linux/liveupdate.h-19-\ninclude/linux/liveupdate.h:20:struct liveupdate_file_handler;\ninclude/linux/liveupdate.h-21-struct liveupdate_flb;\n--\ninclude/linux/liveupdate.h=47=struct liveupdate_file_op_args {\ninclude/linux/liveupdate.h:48:\tstruct liveupdate_file_handler handler;\ninclude/linux/liveupdate.h-49-\tstruct liveupdate_session session;\n--\ninclude/linux/liveupdate.h=77=struct liveupdate_file_ops {\ninclude/linux/liveupdate.h:78:\tbool (can_preserve)(struct liveupdate_file_handler handler,\ninclude/linux/liveupdate.h-79-\t\t\t struct file file);\n--\ninclude/linux/liveupdate.h-91-/\ninclude/linux/liveupdate.h:92: struct liveupdate_file_handler - Represents a handler for a live-updatable file type.\ninclude/linux/liveupdate.h-93- * @ops: Callback functions\n--\ninclude/linux/liveupdate.h-103- /\ninclude/linux/liveupdate.h:104:struct liveupdate_file_handler {\ninclude/linux/liveupdate.h-105-\tconst struct liveupdate_file_ops ops;\n--\ninclude/linux/liveupdate.h=237=int liveupdate_reboot(void);\ninclude/linux/liveupdate.h-238-\ninclude/linux/liveupdate.h:239:int liveupdate_register_file_handler(struct liveupdate_file_handler fh);\ninclude/linux/liveupdate.h:240:void liveupdate_unregister_file_handler(struct liveupdate_file_handler fh);\ninclude/linux/liveupdate.h-241-\ninclude/linux/liveupdate.h:242:int liveupdate_register_flb(struct liveupdate_file_handler fh,\ninclude/linux/liveupdate.h-243-\t\t\t struct liveupdate_flb flb);\ninclude/linux/liveupdate.h:244:void liveupdate_unregister_flb(struct liveupdate_file_handler fh,\ninclude/linux/liveupdate.h-245-\t\t\t struct liveupdate_flb flb);\n--\ninclude/linux/liveupdate.h=268=static inline int liveupdate_reboot(void)\n--\ninclude/linux/liveupdate.h-272-\ninclude/linux/liveupdate.h:273:static inline int liveupdate_register_file_handler(struct liveupdate_file_handler fh)\ninclude/linux/liveupdate.h-274-{\n--\ninclude/linux/liveupdate.h-277-\ninclude/linux/liveupdate.h:278:static inline void liveupdate_unregister_file_handler(struct liveupdate_file_handler fh)\ninclude/linux/liveupdate.h-279-{\n--\ninclude/linux/liveupdate.h-281-\ninclude/linux/liveupdate.h:282:static inline int liveupdate_register_flb(struct liveupdate_file_handler fh,\ninclude/linux/liveupdate.h-283-\t\t\t\t\t struct liveupdate_flb flb)\n--\ninclude/linux/liveupdate.h-287-\ninclude/linux/liveupdate.h:288:static inline void liveupdate_unregister_flb(struct liveupdate_file_handler fh,\ninclude/linux/liveupdate.h-289-\t\t\t\t\t struct liveupdate_flb flb)\n--\ninclude/linux/pci_liveupdate.h=34=struct pci_dev;\n--\ninclude/linux/pci_liveupdate.h-36-#ifdef CONFIG_PCI_LIVEUPDATE\ninclude/linux/pci_liveupdate.h:37:int pci_liveupdate_register_flb(struct liveupdate_file_handler fh);\ninclude/linux/pci_liveupdate.h:38:void pci_liveupdate_unregister_flb(struct liveupdate_file_handler fh);\ninclude/linux/pci_liveupdate.h-39-int pci_liveupdate_preserve(struct pci_dev dev);\n--\ninclude/linux/pci_liveupdate.h=42=bool pci_liveupdate_is_incoming(struct pci_dev dev);\ninclude/linux/pci_liveupdate.h-43-#else\ninclude/linux/pci_liveupdate.h:44:static inline int pci_liveupdate_register_flb(struct liveupdate_file_handler fh)\ninclude/linux/pci_liveupdate.h-45-{\n--\ninclude/linux/pci_liveupdate.h-48-\ninclude/linux/pci_liveupdate.h:49:static inline void pci_liveupdate_unregister_flb(struct liveupdate_file_handler fh)\ninclude/linux/pci_liveupdate.h-50-{\n--\nkernel/liveupdate/luo_file.c-20- * Kernel modules responsible for a specific file type (e.g., memfd, vfio)\nkernel/liveupdate/luo_file.c:21: * register a \u0026struct liveupdate_file_handler. This handler provides a set of\nkernel/liveupdate/luo_file.c-22- * callbacks that LUO invokes at different stages of the update process, most\n--\nkernel/liveupdate/luo_file.c=136=static DEFINE_XARRAY(luo_preserved_files);\n--\nkernel/liveupdate/luo_file.c-139- * struct luo_file - Represents a single preserved file instance.\nkernel/liveupdate/luo_file.c:140: * @fh: Pointer to the \u0026struct liveupdate_file_handler that manages\nkernel/liveupdate/luo_file.c-141- * this type of file.\n--\nkernel/liveupdate/luo_file.c=178=struct luo_file {\nkernel/liveupdate/luo_file.c:179:\tstruct liveupdate_file_handler fh;\nkernel/liveupdate/luo_file.c-180-\tstruct file file;\n--\nkernel/liveupdate/luo_file.c-188-\nkernel/liveupdate/luo_file.c:189:static unsigned long luo_get_id(struct liveupdate_file_handler fh,\nkernel/liveupdate/luo_file.c-190-\t\t\t\tstruct file file)\n--\nkernel/liveupdate/luo_file.c=247=int luo_preserve_file(struct luo_file_set file_set, u64 token, int fd)\n--\nkernel/liveupdate/luo_file.c-249-\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c:250:\tstruct liveupdate_file_handler fh;\nkernel/liveupdate/luo_file.c-251-\tstruct luo_file luo_file;\n--\nkernel/liveupdate/luo_file.c=734=static int luo_file_deserialize_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-736-{\nkernel/liveupdate/luo_file.c:737:\tstruct liveupdate_file_handler fh;\nkernel/liveupdate/luo_file.c-738-\tbool handler_found = false;\n--\nkernel/liveupdate/luo_file.c=870=void luo_file_set_destroy(struct luo_file_set file_set)\n--\nkernel/liveupdate/luo_file.c-877-/*\nkernel/liveupdate/luo_file.c:878: liveupdate_register_file_handler - Register a file handler with LUO.\nkernel/liveupdate/luo_file.c:879: * @fh: Pointer to a caller-allocated \u0026struct liveupdate_file_handler.\nkernel/liveupdate/luo_file.c-880- * The caller must initialize this structure, including a unique\n--\nkernel/liveupdate/luo_file.c-888- /\nkernel/liveupdate/luo_file.c:889:int liveupdate_register_file_handler(struct liveupdate_file_handler fh)\nkernel/liveupdate/luo_file.c-890-{\nkernel/liveupdate/luo_file.c:891:\tstruct liveupdate_file_handler fh_iter;\nkernel/liveupdate/luo_file.c-892-\tint err;\n--\nkernel/liveupdate/luo_file.c-932- Unregisters the file handler from the liveupdate core. This function\nkernel/liveupdate/luo_file.c:933: * reverses the operations of liveupdate_register_file_handler().\nkernel/liveupdate/luo_file.c-934- /\nkernel/liveupdate/luo_file.c:935:void liveupdate_unregister_file_handler(struct liveupdate_file_handler fh)\nkernel/liveupdate/luo_file.c-936-{\n--\nkernel/liveupdate/luo_flb.c=211=void liveupdate_flb_put_incoming(struct liveupdate_flb flb)\n--\nkernel/liveupdate/luo_flb.c-252- /\nkernel/liveupdate/luo_flb.c:253:int luo_flb_file_preserve(struct liveupdate_file_handler fh)\nkernel/liveupdate/luo_flb.c-254-{\n--\nkernel/liveupdate/luo_flb.c-288- /\nkernel/liveupdate/luo_flb.c:289:void luo_flb_file_unpreserve(struct liveupdate_file_handler fh)\nkernel/liveupdate/luo_flb.c-290-{\n--\nkernel/liveupdate/luo_flb.c-309- /\nkernel/liveupdate/luo_flb.c:310:void luo_flb_file_finish(struct liveupdate_file_handler fh)\nkernel/liveupdate/luo_flb.c-311-{\n--\nkernel/liveupdate/luo_flb.c-319-\nkernel/liveupdate/luo_flb.c:320:static void luo_flb_unregister_one(struct liveupdate_file_handler fh,\nkernel/liveupdate/luo_flb.c-321-\t\t\t\t struct liveupdate_flb flb)\n--\nkernel/liveupdate/luo_flb.c-362- /\nkernel/liveupdate/luo_flb.c:363:void luo_flb_unregister_all(struct liveupdate_file_handler fh)\nkernel/liveupdate/luo_flb.c-364-{\n--\nkernel/liveupdate/luo_flb.c-397- /\nkernel/liveupdate/luo_flb.c:398:int liveupdate_register_flb(struct liveupdate_file_handler fh,\nkernel/liveupdate/luo_flb.c-399-\t\t\t struct liveupdate_flb flb)\n--\nkernel/liveupdate/luo_flb.c-477- /\nkernel/liveupdate/luo_flb.c:478:void liveupdate_unregister_flb(struct liveupdate_file_handler fh,\nkernel/liveupdate/luo_flb.c-479-\t\t\t struct liveupdate_flb flb)\n--\nkernel/liveupdate/luo_internal.h=117=void luo_file_set_destroy(struct luo_file_set file_set);\nkernel/liveupdate/luo_internal.h-118-\nkernel/liveupdate/luo_internal.h:119:int luo_flb_file_preserve(struct liveupdate_file_handler fh);\nkernel/liveupdate/luo_internal.h:120:void luo_flb_file_unpreserve(struct liveupdate_file_handler fh);\nkernel/liveupdate/luo_internal.h:121:void luo_flb_file_finish(struct liveupdate_file_handler fh);\nkernel/liveupdate/luo_internal.h:122:void luo_flb_unregister_all(struct liveupdate_file_handler fh);\nkernel/liveupdate/luo_internal.h-123-int __init luo_flb_setup_outgoing(u64 flbs_pa);\n--\nkernel/liveupdate/luo_internal.h=125=void luo_flb_serialize(void);\n--\nkernel/liveupdate/luo_internal.h-127-#ifdef CONFIG_LIVEUPDATE_TEST\nkernel/liveupdate/luo_internal.h:128:void liveupdate_test_register(struct liveupdate_file_handler fh);\nkernel/liveupdate/luo_internal.h-129-#else\nkernel/liveupdate/luo_internal.h:130:static inline void liveupdate_test_register(struct liveupdate_file_handler *fh) { }\nkernel/liveupdate/luo_internal.h-131-#endif\n--\nlib/tests/liveupdate.c=87=static void liveupdate_test_init(void)\n--\nlib/tests/liveupdate.c-114-\n\n" }
13/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26347 output: 35 thoughts: 21 Thoughts: Okay, let's dive into this. Here's my understanding, presented as a personal thought process, given my expertise: Inspecting the `mm/memfd_luo.c` File Handler Right, let's get down to brass tacks. I'm going to take a closer look at the `mm/memfd_luo.c` file. Specifically, I need to understand its file handler implementation. Given that it's in the `mm` directory, I'm expecting it to be deeply involved in memory management, particularly with regard to `memfd_create`. I want to see how it's managing the underlying memory regions associated with file descriptors created by `memfd_create`. I need to figure out the exact mechanisms and data structures in place for this. Does it leverage VMAs? How are pages mapped and unmapped? Are there any clever optimizations in play? This analysis should give me a solid grasp of this module's design and how it affects the larger system. My goal is to understand how this code specifically handles file I/O operations from the file descriptor. I want to see how its behavior is related to the more general page cache functionality.
14/2	2026/10/26 02:26	tool	read-file	0m Args: { "File": "mm/memfd_luo.c", "FirstLine": 1, "LineCount": 80 } Results: { "Contents": " 1:\t// SPDX-License-Identifier: GPL-2.0\n 2:\t\n 3:\t/\n 4:\t Copyright (c) 2025, Google LLC.\n 5:\t * Pasha Tatashin \u003cpasha.tatashin@soleen.com\u003e\n 6:\t \n 7:\t Copyright (C) 2025 Amazon.com Inc. or its affiliates.\n 8:\t * Pratyush Yadav \u003cptyadav@amazon.de\u003e\n 9:\t /\n 10:\t\n 11:\t/\n 12:\t DOC: Memfd Preservation via LUO\n 13:\t \n 14:\t Overview\n 15:\t * ========\n 16:\t \n 17:\t Memory file descriptors (memfd) can be preserved over a kexec using the Live\n 18:\t * Update Orchestrator (LUO) file preservation. This allows userspace to\n 19:\t * transfer its memory contents to the next kernel after a kexec.\n 20:\t \n 21:\t The preservation is not intended to be transparent. Only select properties of\n 22:\t * the file are preserved. All others are reset to default. The preserved\n 23:\t * properties are described below.\n 24:\t \n 25:\t .. note::\n 26:\t * The LUO API is not stabilized yet, so the preserved properties of a memfd\n 27:\t * are also not stable and are subject to backwards incompatible changes.\n 28:\t \n 29:\t .. note::\n 30:\t * Currently a memfd backed by Hugetlb is not supported. Memfds created\n 31:\t * with ``MFD_HUGETLB`` will be rejected.\n 32:\t \n 33:\t Preserved Properties\n 34:\t * ====================\n 35:\t \n 36:\t The following properties of the memfd are preserved across kexec:\n 37:\t \n 38:\t File Contents\n 39:\t * All data stored in the file is preserved.\n 40:\t \n 41:\t File Size\n 42:\t * The size of the file is preserved. Holes in the file are filled by\n 43:\t * allocating pages for them during preservation.\n 44:\t \n 45:\t File Position\n 46:\t * The file position at the time the session is frozen is preserved,\n 47:\t * allowing applications to continue reading/writing from their last\n 48:\t * position.\n 49:\t \n 50:\t File Status Flags\n 51:\t * memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property\n 52:\t * is maintained.\n 53:\t \n 54:\t Seals\n 55:\t * File seals set on the memfd are preserved and re-applied on restore.\n 56:\t * Only seals known to this LUO version (see ``MEMFD_LUO_ALL_SEALS``) may\n 57:\t * be present; preservation fails with ``-EOPNOTSUPP`` otherwise.\n 58:\t \n 59:\t Non-Preserved Properties\n 60:\t * ========================\n 61:\t \n 62:\t All properties which are not preserved must be assumed to be reset to\n 63:\t * default. This section describes some of those properties which may be more of\n 64:\t * note.\n 65:\t \n 66:\t ``FD_CLOEXEC`` flag\n 67:\t * A memfd can be created with the ``MFD_CLOEXEC`` flag that sets the\n 68:\t * ``FD_CLOEXEC`` on the file. This flag is not preserved and must be set\n 69:\t * again after restore via ``fcntl()``.\n 70:\t */\n 71:\t\n 72:\t#define pr_fmt(fmt) KBUILD_MODNAME \": \" fmt\n 73:\t\n 74:\t#include \u003clinux/bits.h\u003e\n 75:\t#include \u003clinux/err.h\u003e\n 76:\t#include \u003clinux/file.h\u003e\n 77:\t#include \u003clinux/io.h\u003e\n 78:\t#include \u003clinux/kexec_handover.h\u003e\n 79:\t#include \u003clinux/kho/abi/memfd.h\u003e\n 80:\t#include \u003clinux/liveupdate.h\u003e\n" }
15/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27795 output: 36 thoughts: 26 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Diving into `mm/memfd_luo.c` for Freeze Implementation Alright, let's get down to brass tacks. I'm taking a look inside `mm/memfd_luo.c` because the question of how this specific module handles `freeze` is the pressing matter. I need to quickly ascertain if the implementation of this functionality is present. We all know how these things can sometimes be handled in unexpected places, so I need to make an informed judgement about this. Let's see what we can dig up, and fast.
16/2	2026/10/26 02:26	tool	read-file	0m Args: { "File": "mm/memfd_luo.c", "FirstLine": 81, "LineCount": 80 } Results: { "Contents": " 81:\t#include \u003clinux/shmem_fs.h\u003e\n 82:\t#include \u003clinux/vmalloc.h\u003e\n 83:\t#include \u003clinux/memfd.h\u003e\n 84:\t#include \u003cuapi/linux/memfd.h\u003e\n 85:\t\n 86:\t#include \"internal.h\"\n 87:\t\n 88:\tstatic int memfd_luo_preserve_folios(struct file file,\n 89:\t\t\t\t\t struct kho_vmalloc kho_vmalloc,\n 90:\t\t\t\t\t struct memfd_luo_folio_ser *out_folios_ser,\n 91:\t\t\t\t\t u64 nr_foliosp)\n 92:\t{\n 93:\t\tstruct inode inode = file_inode(file);\n 94:\t\tstruct memfd_luo_folio_ser folios_ser;\n 95:\t\tunsigned int max_folios;\n 96:\t\tlong i, size, nr_pinned;\n 97:\t\tstruct folio *folios;\n 98:\t\tint err = -EINVAL;\n 99:\t\tpgoff_t offset;\n 100:\t\tu64 nr_folios;\n 101:\t\n 102:\t\tsize = i_size_read(inode);\n 103:\t\t/\n 104:\t\t * If the file has zero size, then the folios and nr_folios properties\n 105:\t\t * are not set.\n 106:\t\t /\n 107:\t\tif (!size) {\n 108:\t\t\tnr_foliosp = 0;\n 109:\t\t\tout_folios_ser = NULL;\n 110:\t\t\treturn 0;\n 111:\t\t}\n 112:\t\n 113:\t\t/\n 114:\t\t * Guess the number of folios based on inode size. Real number might end\n 115:\t\t * up being smaller if there are higher order folios.\n 116:\t\t /\n 117:\t\tmax_folios = PAGE_ALIGN(size) / PAGE_SIZE;\n 118:\t\tfolios = kvmalloc_objs(folios, max_folios);\n 119:\t\tif (!folios)\n 120:\t\t\treturn -ENOMEM;\n 121:\t\n 122:\t\t/\n 123:\t\t Pin the folios so they don't move around behind our back. This also\n 124:\t\t * ensures none of the folios are in CMA -- which ensures they don't\n 125:\t\t * fall in KHO bootmem. It also moves swapped out folios back to memory.\n 126:\t\t \n 127:\t\t A side effect of doing this is that it allocates a folio for all\n 128:\t\t * indices in the file. This might waste memory on sparse memfds. If\n 129:\t\t * that is really a problem in the future, we can have a\n 130:\t\t * memfd_pin_folios() variant that does not allocate a page on empty\n 131:\t\t * slots.\n 132:\t\t /\n 133:\t\tnr_pinned = memfd_pin_folios(file, 0, size - 1, folios, max_folios,\n 134:\t\t\t\t\t \u0026offset);\n 135:\t\tif (nr_pinned \u003c 0) {\n 136:\t\t\terr = nr_pinned;\n 137:\t\t\tpr_err(\"failed to pin folios: %d\\n\", err);\n 138:\t\t\tgoto err_free_folios;\n 139:\t\t}\n 140:\t\tnr_folios = nr_pinned;\n 141:\t\n 142:\t\tfolios_ser = vcalloc(nr_folios, sizeof(folios_ser));\n 143:\t\tif (!folios_ser) {\n 144:\t\t\terr = -ENOMEM;\n 145:\t\t\tgoto err_unpin;\n 146:\t\t}\n 147:\t\n 148:\t\tfor (i = 0; i \u003c nr_folios; i++) {\n 149:\t\t\tstruct memfd_luo_folio_ser pfolio = \u0026folios_ser[i];\n 150:\t\t\tstruct folio folio = folios[i];\n 151:\t\n 152:\t\t\terr = kho_preserve_folio(folio);\n 153:\t\t\tif (err)\n 154:\t\t\t\tgoto err_unpreserve;\n 155:\t\n 156:\t\t\tfolio_lock(folio);\n 157:\t\n 158:\t\t\t/\n 159:\t\t\t A dirty folio is one which has been written to. A clean folio\n 160:\t\t\t * is its opposite. Since a clean folio does not carry user\n" }
17/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29200 output: 37 thoughts: 23 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Diving Deeper into `mm/memfd_luo.c` for `freeze` Alright, so we're talking about `mm/memfd_luo.c`, and my initial focus is honed in on the `freeze` function. I need to get a handle on what's going on here. Considering the context, I'm expecting this `freeze` function is likely responsible for temporarily suspending or quiescing some aspect of memory management related to memfd files. Given Luo's involvement, it's probably handling some specific optimization or interaction within that subsystem. My immediate questions are: What exactly is being "frozen"? Is it the mappings? The allocation state? Is it related to checkpointing or snapshotting? And, more importantly, how does this fit in with the overall memfd lifecycle? I'm anticipating there's some interesting locking or synchronization going on around that function too, I better make a note to look at that as well.
18/2	2026/10/26 02:26	tool	read-file	0m Args: { "File": "mm/memfd_luo.c", "FirstLine": 380, "LineCount": 80 } Results: { "Contents": " 380:\t\t\t\tcontinue;\n 381:\t\t\t}\n 382:\t\n 383:\t\t\tfolio_put(folio);\n 384:\t\t}\n 385:\t}\n 386:\t\n 387:\tstatic void memfd_luo_finish(struct liveupdate_file_op_args args)\n 388:\t{\n 389:\t\tstruct memfd_luo_folio_ser folios_ser;\n 390:\t\tstruct memfd_luo_ser ser;\n 391:\t\n 392:\t\t/\n 393:\t\t * If retrieve was successful, nothing to do. If it failed, retrieve()\n 394:\t\t * already cleaned up everything it could. So nothing to do there\n 395:\t\t * either. Only need to clean up when retrieve was not called.\n 396:\t\t /\n 397:\t\tif (args-\u003eretrieve_status)\n 398:\t\t\treturn;\n 399:\t\n 400:\t\tser = phys_to_virt(args-\u003eserialized_data);\n 401:\t\tif (!ser)\n 402:\t\t\treturn;\n 403:\t\n 404:\t\tif (ser-\u003enr_folios) {\n 405:\t\t\tfolios_ser = kho_restore_vmalloc(\u0026ser-\u003efolios);\n 406:\t\t\tif (!folios_ser)\n 407:\t\t\t\tgoto out;\n 408:\t\n 409:\t\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\n 410:\t\t\tvfree(folios_ser);\n 411:\t\t}\n 412:\t\n 413:\tout:\n 414:\t\tkho_restore_free(ser);\n 415:\t}\n 416:\t\n 417:\tstatic int memfd_luo_retrieve_folios(struct file file,\n 418:\t\t\t\t\t struct memfd_luo_folio_ser folios_ser,\n 419:\t\t\t\t\t u64 nr_folios)\n 420:\t{\n 421:\t\tstruct inode inode = file_inode(file);\n 422:\t\tstruct address_space mapping = inode-\u003ei_mapping;\n 423:\t\tstruct folio folio;\n 424:\t\tlong npages, nr_added_pages = 0;\n 425:\t\tint err = -EIO;\n 426:\t\tlong i;\n 427:\t\n 428:\t\tfor (i = 0; i \u003c nr_folios; i++) {\n 429:\t\t\tconst struct memfd_luo_folio_ser pfolio = \u0026folios_ser[i];\n 430:\t\t\tphys_addr_t phys;\n 431:\t\t\tu64 index;\n 432:\t\t\tint flags;\n 433:\t\n 434:\t\t\tif (!pfolio-\u003epfn)\n 435:\t\t\t\tcontinue;\n 436:\t\n 437:\t\t\tphys = PFN_PHYS(pfolio-\u003epfn);\n 438:\t\t\tfolio = kho_restore_folio(phys);\n 439:\t\t\tif (!folio) {\n 440:\t\t\t\tpr_err(\"Unable to restore folio at physical address: %llx\\n\",\n 441:\t\t\t\t phys);\n 442:\t\t\t\terr = -EIO;\n 443:\t\t\t\tgoto put_folios;\n 444:\t\t\t}\n 445:\t\t\tindex = pfolio-\u003eindex;\n 446:\t\t\tflags = pfolio-\u003eflags;\n 447:\t\n 448:\t\t\t/ Set up the folio for insertion. */\n 449:\t\t\t__folio_set_locked(folio);\n 450:\t\t\t__folio_set_swapbacked(folio);\n 451:\t\n 452:\t\t\terr = mem_cgroup_charge(folio, NULL, mapping_gfp_mask(mapping));\n 453:\t\t\tif (err) {\n 454:\t\t\t\tpr_err(\"shmem: failed to charge folio index %ld: %d\\n\",\n 455:\t\t\t\t i, err);\n 456:\t\t\t\tgoto unlock_folio;\n 457:\t\t\t}\n 458:\t\n 459:\t\t\terr = shmem_add_to_page_cache(folio, mapping, index, NULL,\n" }
19/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30600 output: 36 thoughts: 20 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: Analyzing the `liveupdate_file_ops` in `memfd_luo` Alright, so the task at hand is to trace the definition of `liveupdate_file_ops`. My first instinct is to zero in on where `memfd_luo` itself sets up this particular structure. I need to find where the `liveupdate_file_ops` function pointers are assigned. This could be in a module initialization function, maybe during some object creation within the `memfd_luo` implementation, or perhaps even in a helper library that the project uses. I'll need to dig through the code base and see where this structure is initialized. Knowing the exact structure definition might help narrow the search. Ultimately, I'm trying to understand the control flow that dictates the operations associated with the live update functionality in this module. Let's see how this thing is actually defined.
20/2	2026/10/26 02:26	tool	grepper	0m Args: { "Expression": "liveupdate_file_ops", "PathPrefixes": [ "mm/memfd_luo.c" ] } Results: { "Output": "mm/memfd_luo.c=588=static unsigned long memfd_luo_get_id(struct file *file)\n--\nmm/memfd_luo.c-592-\nmm/memfd_luo.c:593:static const struct liveupdate_file_ops memfd_luo_file_ops = {\nmm/memfd_luo.c-594-\t.freeze = memfd_luo_freeze,\n" }
21/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30996 output: 37 thoughts: 26 Thoughts: Okay, here's my interpretation of what's going on, thinking as if these are my thoughts: Diving into `mm/memfd_luo.c` Alright, time to get my hands dirty. I'm going to zero in on lines 580 through 610 within `mm/memfd_luo.c`. This specific section of code must be dealing with a critical aspect of memfd, potentially related to a core memory management functionality within the Luo filesystem support. I suspect this is where the interesting bit happens, given its placement within the file, likely involving some intricacies of memory file descriptor management, or interactions with the underlying virtual memory system. I'll need to carefully parse the logic here, paying close attention to any subtle data structures or potential locking mechanisms that could be at play. I'm anticipating some nuances in how the memfd implementation interacts with the file system layer, particularly if it's optimizing how memory files are handled. I'm ready to dig in and understand this more deeply.
22/2	2026/10/26 02:26	tool	read-file	0m Args: { "File": "mm/memfd_luo.c", "FirstLine": 580, "LineCount": 40 } Results: { "Contents": " 580:\tstatic bool memfd_luo_can_preserve(struct liveupdate_file_handler handler,\n 581:\t\t\t\t\t struct file file)\n 582:\t{\n 583:\t\tstruct inode inode = file_inode(file);\n 584:\t\n 585:\t\treturn shmem_file(file) \u0026\u0026 !inode-\u003ei_nlink;\n 586:\t}\n 587:\t\n 588:\tstatic unsigned long memfd_luo_get_id(struct file file)\n 589:\t{\n 590:\t\treturn (unsigned long)file_inode(file);\n 591:\t}\n 592:\t\n 593:\tstatic const struct liveupdate_file_ops memfd_luo_file_ops = {\n 594:\t\t.freeze = memfd_luo_freeze,\n 595:\t\t.finish = memfd_luo_finish,\n 596:\t\t.retrieve = memfd_luo_retrieve,\n 597:\t\t.preserve = memfd_luo_preserve,\n 598:\t\t.unpreserve = memfd_luo_unpreserve,\n 599:\t\t.can_preserve = memfd_luo_can_preserve,\n 600:\t\t.get_id = memfd_luo_get_id,\n 601:\t\t.owner = THIS_MODULE,\n 602:\t};\n 603:\t\n 604:\tstatic struct liveupdate_file_handler memfd_luo_handler = {\n 605:\t\t.ops = \u0026memfd_luo_file_ops,\n 606:\t\t.compatible = MEMFD_LUO_FH_COMPATIBLE,\n 607:\t};\n 608:\t\n 609:\tstatic int __init memfd_luo_init(void)\n 610:\t{\n 611:\t\tint err = liveupdate_register_file_handler(\u0026memfd_luo_handler);\n 612:\t\n 613:\t\tif (err \u0026\u0026 err != -EOPNOTSUPP) {\n 614:\t\t\tpr_err(\"Could not register luo filesystem handler: %pe\\n\",\n 615:\t\t\t ERR_PTR(err));\n 616:\t\n 617:\t\t\treturn err;\n 618:\t\t}\n 619:\t\n" }
23/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31901 output: 37 thoughts: 51 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Initial Assessment of a Novel Kernel Function Well, isn't this interesting? `memfd_luo_freeze`... That's a new one. Given the naming convention and my background, I immediately suspect this likely relates to some kind of memory file freezing mechanism within the kernel. My initial hypothesis is that it could be related to memory management, possibly snapshotting, or perhaps even live migration scenarios. Let's dig in and see. Right, let's jump straight to `mm/memfd_luo.c` and take a look at the code. Lines 300-380 should be a good starting point to analyze the `memfd_luo_freeze` function itself. I want to see how it's implemented, what data structures it interacts with, and what its overall purpose is in the broader kernel context. This quick examination should give me a solid foundation for evaluating its design and potential implications.
24/2	2026/10/26 02:26	tool	read-file	0m Args: { "File": "mm/memfd_luo.c", "FirstLine": 300, "LineCount": 80 } Results: { "Contents": " 300:\t\tser-\u003esize = inode_size;\n 301:\t\tser-\u003eseals = seals;\n 302:\t\n 303:\t\terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\n 304:\t\t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n 305:\t\tif (err)\n 306:\t\t\tgoto err_free_ser;\n 307:\t\n 308:\t\tser-\u003enr_folios = nr_folios;\n 309:\t\tinode_unlock(inode);\n 310:\t\n 311:\t\targs-\u003eprivate_data = folios_ser;\n 312:\t\targs-\u003eserialized_data = virt_to_phys(ser);\n 313:\t\n 314:\t\treturn 0;\n 315:\t\n 316:\terr_free_ser:\n 317:\t\tkho_unpreserve_free(ser);\n 318:\terr_unlock:\n 319:\t\tshmem_freeze(inode, false);\n 320:\t\tinode_unlock(inode);\n 321:\t\treturn err;\n 322:\t}\n 323:\t\n 324:\tstatic int memfd_luo_freeze(struct liveupdate_file_op_args args)\n 325:\t{\n 326:\t\tstruct memfd_luo_ser ser;\n 327:\t\n 328:\t\tif (WARN_ON_ONCE(!args-\u003eserialized_data))\n 329:\t\t\treturn -EINVAL;\n 330:\t\n 331:\t\tser = phys_to_virt(args-\u003eserialized_data);\n 332:\t\n 333:\t\t/\n 334:\t\t The pos might have changed since prepare. Everything else stays the\n 335:\t\t * same.\n 336:\t\t /\n 337:\t\tser-\u003epos = args-\u003efile-\u003ef_pos;\n 338:\t\n 339:\t\treturn 0;\n 340:\t}\n 341:\t\n 342:\tstatic void memfd_luo_unpreserve(struct liveupdate_file_op_args args)\n 343:\t{\n 344:\t\tstruct inode inode = file_inode(args-\u003efile);\n 345:\t\tstruct memfd_luo_ser ser;\n 346:\t\n 347:\t\tif (WARN_ON_ONCE(!args-\u003eserialized_data))\n 348:\t\t\treturn;\n 349:\t\n 350:\t\tinode_lock(inode);\n 351:\t\tshmem_freeze(inode, false);\n 352:\t\n 353:\t\tser = phys_to_virt(args-\u003eserialized_data);\n 354:\t\n 355:\t\tmemfd_luo_unpreserve_folios(\u0026ser-\u003efolios, args-\u003eprivate_data,\n 356:\t\t\t\t\t ser-\u003enr_folios);\n 357:\t\n 358:\t\tkho_unpreserve_free(ser);\n 359:\t\tinode_unlock(inode);\n 360:\t}\n 361:\t\n 362:\tstatic void memfd_luo_discard_folios(const struct memfd_luo_folio_ser folios_ser,\n 363:\t\t\t\t\t u64 nr_folios)\n 364:\t{\n 365:\t\tu64 i;\n 366:\t\n 367:\t\tfor (i = 0; i \u003c nr_folios; i++) {\n 368:\t\t\tconst struct memfd_luo_folio_ser pfolio = \u0026folios_ser[i];\n 369:\t\t\tstruct folio *folio;\n 370:\t\t\tphys_addr_t phys;\n 371:\t\n 372:\t\t\tif (!pfolio-\u003epfn)\n 373:\t\t\t\tcontinue;\n 374:\t\n 375:\t\t\tphys = PFN_PHYS(pfolio-\u003epfn);\n 376:\t\t\tfolio = kho_restore_folio(phys);\n 377:\t\t\tif (!folio) {\n 378:\t\t\t\tpr_warn_ratelimited(\"Unable to restore folio at physical address: %llx\\n\",\n 379:\t\t\t\t\t\t phys);\n" }
25/2	2026/10/26 02:26	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 33313 output: 39 thoughts: 801 Thoughts: Analyzing the `luo_session_freeze` Operation Okay, let's break down what's happening within the `luo_session_freeze` function and its related interactions, as well as the related functions involved. I'm focusing on the locking, freezing, and unfreezing of files within a live update session. First, within `luo_session_freeze`, the function takes a `luo_session` and a `luo_ucmd` (user command) as arguments. A `liveupdate_session_freeze` struct is cast from the ucmd. It verifies a reserved field, returning an error if set (likely for future expansion). Crucially, it acquires the session's mutex using `guard(mutex)`. This is my first indicator of concurrency control. If the session is already frozen by a user, I immediately return `EBUSY`, preventing a double-freeze. The core action is calling `luo_file_freeze` on the session's `file_set`. If this operation fails, I return the error. Only if the file freeze is successful, the function sends a response to the user with `luo_ucmd_respond` and sets the `user_frozen` flag to `true`. If this response also fails, I must unfreeze the files first. The `IOCTL_OP` macro links `LIVEUPDATE_SESSION_FREEZE` to `luo_session_freeze`, which is fairly standard. Moving on to `luo_session_release`, I observe that when the session is released (i.e., closed or destroyed), the mutex is again used. If the session was frozen by the user (`user_frozen`), the function calls `luo_file_unfreeze` to release the files, as well as `luo_file_unpreserve_files` for good measure. This makes sure that the session cleans up properly on exit. Now, `luo_session_preserve_fd` has a similar lock, checking the `user_frozen` state. If it's already frozen, the command also returns `EBUSY`. In `luo_session_serialize_one`, I see a conditional freeze. The mutex is acquired. It's only if the session isn't already user-frozen, that the function calls `luo_file_freeze`. This suggests the function is freezing files automatically during serialization. Then, it populates the `ser` (likely serialization data) structure with session name and the file set data from the session. Finally, `luo_session_unserialize_one` handles the reverse process. It grabs the mutex. Here, a comment clarifies an important distinction: if the session was not frozen by the user (`!session->user_frozen`), implying an auto-freeze by `luo_session_serialize_one`, it calls `luo_file_unfreeze`. This implies user-initiated freezes must persist until session closure. The serialization struct itself is reset. I also see that `luo_file_freeze` and `luo_file_unfreeze` now lack a `file_set_ser` parameter because the data is now serialized internally within `luo_file_freeze`, as it prepares the information for `kho_block_set`. This is a straightforward refactoring.
26/2	2026/10/26 02:27	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_file.c", "FirstLine": 460, "LineCount": 60 } Results: { "Contents": " 460:\t * metadata—the handler's compatible string, the user token, and the final\n 461:\t * private data handle—into the pre-allocated serialization blocks\n 462:\t * (file_set-\u003eblock_set) that will be handed over to the next kernel via KHO.\n 463:\t \n 464:\t Error Handling (Rollback):\n 465:\t * This function is atomic. If any handler's .freeze() operation fails, the\n 466:\t * __luo_file_unfreeze() helper is immediately called to invoke the .unfreeze()\n 467:\t * op on all files that were successfully frozen before the point of failure,\n 468:\t * rolling them back to an unfrozen state, and an error is returned to the\n 469:\t * caller, canceling the live update if called from the reboot() path.\n 470:\t \n 471:\t Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path.\n 472:\t * Return: 0 on success, or a negative errno on failure.\n 473:\t /\n 474:\tint luo_file_freeze(struct luo_file_set file_set)\n 475:\t{\n 476:\t\tstruct luo_file luo_file;\n 477:\t\tstruct kho_block_set_it it;\n 478:\t\tint err;\n 479:\t\n 480:\t\tif (!file_set-\u003ecount)\n 481:\t\t\treturn 0;\n 482:\t\n 483:\t\tkho_block_set_it_init(\u0026it, \u0026file_set-\u003eblock_set);\n 484:\t\n 485:\t\tlist_for_each_entry(luo_file, \u0026file_set-\u003efiles_list, list) {\n 486:\t\t\tstruct luo_file_ser file_ser = kho_block_set_it_reserve_entry(\u0026it);\n 487:\t\n 488:\t\t\t/* This should not fail normally as blocks were pre-allocated /\n 489:\t\t\tif (WARN_ON_ONCE(!file_ser)) {\n 490:\t\t\t\terr = -ENOSPC;\n 491:\t\t\t\tgoto err_unfreeze;\n 492:\t\t\t}\n 493:\t\n 494:\t\t\terr = luo_file_freeze_one(file_set, luo_file);\n 495:\t\t\tif (err \u003c 0) {\n 496:\t\t\t\tpr_warn(\"Freeze failed for token[%#0llx] handler[%s] err[%pe]\\n\",\n 497:\t\t\t\t\tluo_file-\u003etoken, luo_file-\u003efh-\u003ecompatible,\n 498:\t\t\t\t\tERR_PTR(err));\n 499:\t\t\t\tgoto err_unfreeze;\n 500:\t\t\t}\n 501:\t\n 502:\t\t\tstrscpy(file_ser-\u003ecompatible, luo_file-\u003efh-\u003ecompatible,\n 503:\t\t\t\tsizeof(file_ser-\u003ecompatible));\n 504:\t\t\tfile_ser-\u003edata = luo_file-\u003eserialized_data;\n 505:\t\t\tfile_ser-\u003etoken = luo_file-\u003etoken;\n 506:\t\t}\n 507:\t\n 508:\t\treturn 0;\n 509:\t\n 510:\terr_unfreeze:\n 511:\t\t__luo_file_unfreeze(file_set, luo_file);\n 512:\t\n 513:\t\treturn err;\n 514:\t}\n 515:\t\n 516:\t/\n 517:\t luo_file_unfreeze - Unfreezes all files in a file_set and clear serialization\n 518:\t * @file_set: The file_set whose files are to be unfrozen.\n 519:\t *\n" }
27/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35878 output: 39 thoughts: 71 Thoughts: Here's my summary, as I delve into this intriguing interaction: Investigating the `/dev/liveupdate` Mechanism Okay, so `/dev/liveupdate` is the key. And it's using device nodes and session file descriptors to facilitate something... interesting. My mind immediately jumps to the user-space interaction. How precisely does a user-space application leverage this `/dev/liveupdate` interface? I need to understand this to grasp the whole picture. Alright, let's dive into the kernel code then. Specifically, I'm zeroing in on `kernel/liveupdate/luo_core.c`. My focus needs to be around the `luo_ioctl_create_session` function, and the broader `luo_ioctl` function. These two are critical; they're the likely entry points for user-space requests. The `_create_session` function has to be the most important. It'll define how the sessions are established. I'll need to follow the data flows from there.
28/2	2026/10/26 02:27	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 270, "LineCount": 60 } Results: { "Contents": " 270:\tstatic int luo_ioctl_create_session(struct luo_ucmd ucmd)\n 271:\t{\n 272:\t\tstruct liveupdate_ioctl_create_session argp = ucmd-\u003ecmd;\n 273:\t\tstruct file file;\n 274:\t\tint err;\n 275:\t\n 276:\t\targp-\u003efd = get_unused_fd_flags(O_CLOEXEC);\n 277:\t\tif (argp-\u003efd \u003c 0)\n 278:\t\t\treturn argp-\u003efd;\n 279:\t\n 280:\t\terr = luo_session_create(argp-\u003ename, \u0026file);\n 281:\t\tif (err)\n 282:\t\t\tgoto err_put_fd;\n 283:\t\n 284:\t\terr = luo_ucmd_respond(ucmd, sizeof(argp));\n 285:\t\tif (err)\n 286:\t\t\tgoto err_put_file;\n 287:\t\n 288:\t\tfd_install(argp-\u003efd, file);\n 289:\t\n 290:\t\treturn 0;\n 291:\t\n 292:\terr_put_file:\n 293:\t\tfput(file);\n 294:\terr_put_fd:\n 295:\t\tput_unused_fd(argp-\u003efd);\n 296:\t\n 297:\t\treturn err;\n 298:\t}\n 299:\t\n 300:\tstatic int luo_ioctl_retrieve_session(struct luo_ucmd ucmd)\n 301:\t{\n 302:\t\tstruct liveupdate_ioctl_retrieve_session argp = ucmd-\u003ecmd;\n 303:\t\tstruct file file;\n 304:\t\tint err;\n 305:\t\n 306:\t\targp-\u003efd = get_unused_fd_flags(O_CLOEXEC);\n 307:\t\tif (argp-\u003efd \u003c 0)\n 308:\t\t\treturn argp-\u003efd;\n 309:\t\n 310:\t\terr = luo_session_retrieve(argp-\u003ename, \u0026file);\n 311:\t\tif (err \u003c 0)\n 312:\t\t\tgoto err_put_fd;\n 313:\t\n 314:\t\terr = luo_ucmd_respond(ucmd, sizeof(argp));\n 315:\t\tif (err)\n 316:\t\t\tgoto err_put_file;\n 317:\t\n 318:\t\tfd_install(argp-\u003efd, file);\n 319:\t\n 320:\t\treturn 0;\n 321:\t\n 322:\terr_put_file:\n 323:\t\tfput(file);\n 324:\terr_put_fd:\n 325:\t\tput_unused_fd(argp-\u003efd);\n 326:\t\n 327:\t\treturn err;\n 328:\t}\n 329:\t\n" }
29/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37018 output: 39 thoughts: 52 Thoughts: Okay, let's dive into this. Here's what I'm thinking: Investigating the Live Update Mechanism Right, I need to understand this `/dev/liveupdate` device and the `liveupdate_enabled()` function. I want to see exactly how they're interacting. My immediate plan is to jump into the code. Specifically, lines 230 through 270 in `kernel/liveupdate/luo_core.c` seem like the prime location to start. I'm expecting to find the key logic there, the nitty-gritty of how `/dev/liveupdate` is accessed and whether the Live Update system is actually active. I'm hoping to understand the control flow and conditions that govern its behavior. Time to get to the details.
30/2	2026/10/26 02:27	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 230, "LineCount": 45 } Results: { "Contents": " 230:\t\n 231:\t\tluo_flb_serialize();\n 232:\t\n 233:\t\treturn 0;\n 234:\t}\n 235:\t\n 236:\t/*\n 237:\t liveupdate_enabled - Check if the live update feature is enabled.\n 238:\t \n 239:\t This function returns the state of the live update feature flag, which\n 240:\t * can be controlled via the ``liveupdate`` kernel command-line parameter.\n 241:\t \n 242:\t @return true if live update is enabled, false otherwise.\n 243:\t /\n 244:\tbool liveupdate_enabled(void)\n 245:\t{\n 246:\t\treturn luo_global.enabled;\n 247:\t}\n 248:\t\n 249:\t/\n 250:\t DOC: LUO ioctl Interface\n 251:\t \n 252:\t The IOCTL user-space control interface for the LUO subsystem.\n 253:\t * It registers a character device, typically found at ``/dev/liveupdate``,\n 254:\t * which allows a userspace agent to manage the LUO state machine and its\n 255:\t * associated resources, such as preservable file descriptors.\n 256:\t \n 257:\t To ensure that the state machine is controlled by a single entity, access\n 258:\t * to this device is exclusive: only one process is permitted to have\n 259:\t * ``/dev/liveupdate`` open at any given time. Subsequent open attempts will\n 260:\t * fail with -EBUSY until the first process closes its file descriptor.\n 261:\t * This singleton model simplifies state management by preventing conflicting\n 262:\t * commands from multiple userspace agents.\n 263:\t /\n 264:\t\n 265:\tstruct luo_device_state {\n 266:\t\tstruct miscdevice miscdev;\n 267:\t\tatomic_t in_use;\n 268:\t};\n 269:\t\n 270:\tstatic int luo_ioctl_create_session(struct luo_ucmd ucmd)\n 271:\t{\n 272:\t\tstruct liveupdate_ioctl_create_session argp = ucmd-\u003ecmd;\n 273:\t\tstruct file file;\n 274:\t\tint err;\n" }
31/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37923 output: 38 thoughts: 43 Thoughts: Okay, let's break this down. Investigating the Live Update Configuration Alright, before I dive in any deeper, I need to verify a fundamental setting. I need to quickly ascertain the state of `luo_global.enabled`. That variable controls the overall live update functionality, and I can't proceed without knowing whether it's active. Once I know that, I'll have a better picture of what's going on. Next, I need to see the actual implementation. Lines 75-100 within `kernel/liveupdate/luo_core.c` seem like a logical place to look. That range likely contains initialization, the core logic that checks the setting, or the functions that are executed based on its value. I'm hoping I can find the answer quickly by just going straight to the code.
32/2	2026/10/26 02:27	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 75, "LineCount": 35 } Results: { "Contents": " 75:\t /\n 76:\tDECLARE_RWSEM(luo_register_rwlock);\n 77:\t\n 78:\tstatic int __init early_liveupdate_param(char buf)\n 79:\t{\n 80:\t\treturn kstrtobool(buf, \u0026luo_global.enabled);\n 81:\t}\n 82:\tearly_param(\"liveupdate\", early_liveupdate_param);\n 83:\t\n 84:\tstatic int __init luo_early_startup(void)\n 85:\t{\n 86:\t\tphys_addr_t luo_ser_phys;\n 87:\t\tstruct luo_ser luo_ser;\n 88:\t\tsize_t len;\n 89:\t\tint err;\n 90:\t\n 91:\t\tif (!kho_is_enabled()) {\n 92:\t\t\tif (liveupdate_enabled())\n 93:\t\t\t\tpr_warn(\"Disabling liveupdate because KHO is disabled\\n\");\n 94:\t\t\tluo_global.enabled = false;\n 95:\t\t\treturn 0;\n 96:\t\t}\n 97:\t\n 98:\t\t/ Retrieve LUO state from KHO. */\n 99:\t\terr = kho_retrieve_subtree(LUO_KHO_ENTRY_NAME, \u0026luo_ser_phys, \u0026len);\n 100:\t\tif (err) {\n 101:\t\t\tif (err != -ENOENT) {\n 102:\t\t\t\tpr_err(\"failed to retrieve LUO state '%s' from KHO: %pe\\n\",\n 103:\t\t\t\t LUO_KHO_ENTRY_NAME, ERR_PTR(err));\n 104:\t\t\t\treturn err;\n 105:\t\t\t}\n 106:\t\n 107:\t\t\treturn 0;\n 108:\t\t}\n 109:\t\n" }
33/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38669 output: 19 thoughts: 31 Thoughts: Okay, let's break this down. Investigating the KHO Enablement Right, so the first thing I need to figure out is whether the KHO functionality is currently enabled. I'll start by checking the `kho_is_enabled()` function. That's the logical starting point. But, how is KHO enabled, exactly? I need to understand the mechanism behind it. The most straightforward way to discover the implementation is to search the codebase for where `kho_is_enabled` is actually defined and used. A quick `grep` will be just the ticket. Time to get that search running and see what comes up. That should give me the context I need.
34/2	2026/10/26 02:27	tool	grepper	0m Args: { "Expression": "kho_is_enabled" } Results: { "Output": "include/linux/kexec_handover.h=14=struct page;\n--\ninclude/linux/kexec_handover.h-16-#ifdef CONFIG_KEXEC_HANDOVER\ninclude/linux/kexec_handover.h:17:bool kho_is_enabled(void);\ninclude/linux/kexec_handover.h-18-bool is_kho_boot(void);\n--\ninclude/linux/kexec_handover.h=44=static inline enum migratetype kho_bootmem_migratetype(unsigned long pfn,\n--\ninclude/linux/kexec_handover.h-51-#else\ninclude/linux/kexec_handover.h:52:static inline bool kho_is_enabled(void)\ninclude/linux/kexec_handover.h-53-{\n--\nkernel/kexec_file.c=833=static int kexec_calculate_store_digests(struct kimage *image)\n--\nkernel/kexec_file.c-865-\tif (image-\u003etype != KEXEC_TYPE_CRASH \u0026\u0026\nkernel/kexec_file.c:866:\t (kho_is_enabled() \|\| kexec_only_cma_segments(image))) {\nkernel/kexec_file.c-867-\t\tpr_debug(\"disabling checksum verification in purgatory\\n\");\n--\nkernel/liveupdate/kexec_handover.c=70=static bool kho_enable __ro_after_init = IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT);\nkernel/liveupdate/kexec_handover.c-71-\nkernel/liveupdate/kexec_handover.c:72:bool kho_is_enabled(void)\nkernel/liveupdate/kexec_handover.c-73-{\n--\nkernel/liveupdate/kexec_handover.c-75-}\nkernel/liveupdate/kexec_handover.c:76:EXPORT_SYMBOL_GPL(kho_is_enabled);\nkernel/liveupdate/kexec_handover.c-77-\n--\nkernel/liveupdate/luo_core.c=84=static int __init luo_early_startup(void)\n--\nkernel/liveupdate/luo_core.c-90-\nkernel/liveupdate/luo_core.c:91:\tif (!kho_is_enabled()) {\nkernel/liveupdate/luo_core.c-92-\t\tif (liveupdate_enabled())\n--\nlib/test_kho.c=314=static int __init kho_test_init(void)\n--\nlib/test_kho.c-318-\nlib/test_kho.c:319:\tif (!kho_is_enabled())\nlib/test_kho.c-320-\t\treturn 0;\n--\nmm/memblock.c=2668=static int __init reserve_mem_init(void)\nmm/memblock.c-2669-{\nmm/memblock.c:2670:\tif (!kho_is_enabled() \|\| !reserved_mem_count)\nmm/memblock.c-2671-\t\treturn 0;\n" }
35/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 39647 output: 20 thoughts: 108 Thoughts: Investigating the Kernel Live Update Handover Mechanism Okay, so I'm looking into the live update process, specifically the kexec handover. I've got `kernel/liveupdate/kexec_handover.c` open. Right off the bat, I see `kho_enable` is declared with `__ro_afterinit` and initialized with `IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT)`. My initial thought is, this looks like a boot-time configurable option, perhaps set by a default config value. I need to understand how the system determines whether `liveupdate_enabled()` is actually active. My immediate question is: does it depend solely on the `liveupdate=on` boot parameter, or `liveupdate_param`, or is there also a default configuration option? I need to check the config to see if there is a default value for enabling live updates. I need to trace this back to the configuration to fully grasp the control flow here.
36/2	2026/10/26 02:27	tool	grepper	0m Args: { "Expression": "early_liveupdate_param" } Results: { "Output": "kernel/liveupdate/luo_core.c=76=DECLARE_RWSEM(luo_register_rwlock);\nkernel/liveupdate/luo_core.c-77-\nkernel/liveupdate/luo_core.c:78:static int __init early_liveupdate_param(char *buf)\nkernel/liveupdate/luo_core.c-79-{\n--\nkernel/liveupdate/luo_core.c-81-}\nkernel/liveupdate/luo_core.c:82:early_param(\"liveupdate\", early_liveupdate_param);\nkernel/liveupdate/luo_core.c-83-\n" }
37/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 40154 output: 38 thoughts: 34 Thoughts: Here's a summary of my thought process, as requested: Diving into the Live Update Core Okay, I need to understand the global structure used in this live update process. Let's start by zeroing in on the core file, specifically `kernel/liveupdate/luo_core.c`. I'm going to jump to lines 65 through 75. That should be where the definition of `luo_global` should reside. I expect it's going to be a key data structure for coordinating the live update functionality, and I need to review its members to get a handle on how this system is architected. I'll be looking for things like mutexes, state variables, pointers to other crucial data, and anything that gives me a clear picture of how the live update logic is managed.
38/2	2026/10/26 02:27	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 60, "LineCount": 20 } Results: { "Contents": " 60:\t#include \u003clinux/rwsem.h\u003e\n 61:\t#include \u003clinux/sizes.h\u003e\n 62:\t#include \u003clinux/string.h\u003e\n 63:\t\n 64:\t#include \"kexec_handover_internal.h\"\n 65:\t#include \"luo_internal.h\"\n 66:\t\n 67:\tstatic struct {\n 68:\t\tbool enabled;\n 69:\t\tstruct luo_ser luo_ser_out;\n 70:\t\tu64 liveupdate_num;\n 71:\t} luo_global;\n 72:\t\n 73:\t/\n 74:\t * luo_register_rwlock - Protects registration of file handlers and FLBs.\n 75:\t /\n 76:\tDECLARE_RWSEM(luo_register_rwlock);\n 77:\t\n 78:\tstatic int __init early_liveupdate_param(char buf)\n 79:\t{\n" }
39/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 40668 output: 38 thoughts: 51 Thoughts: Okay, here's my take on those thoughts, framed as my own: Initial Configuration and Startup Logic for `luo_global.enabled` Right, so, let's nail down this `luo_global.enabled` flag. It seems pretty straightforward on the face of it: by default, it's off. No surprises there. That's a good fail-safe, right? Assume disabled until explicitly told otherwise. Now, the triggers. The critical bits are `liveupdate=on` or `liveupdate=1`. These are the explicit switches that are going to flip this thing on, enabling whatever functionality it controls. Makes sense. Those are our overrides. But...wait a minute. I have a hunch there might be more to it than just that simple check. There's always some nuance in these things. I need to be absolutely sure. My intuition is nudging me to double-check the startup sequence, specifically the `luo_early_startup` code, lines 95-135. It could be that this is a little more complicated than a straight up boolean, and potentially the flag state is retrieved from somewhere, or altered based on some other condition. I need to review this section of the code very carefully to be absolutely certain. Just because it appears simple doesn't mean it is simple, and I need to account for any edge cases in there. Gotta cover my bases. So, `liveupdate` is the primary driver, but I need to confirm there aren't any sneaky secondary influences.
40/2	2026/10/26 02:27	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 95, "LineCount": 40 } Results: { "Contents": " 95:\t\t\treturn 0;\n 96:\t\t}\n 97:\t\n 98:\t\t/* Retrieve LUO state from KHO. /\n 99:\t\terr = kho_retrieve_subtree(LUO_KHO_ENTRY_NAME, \u0026luo_ser_phys, \u0026len);\n 100:\t\tif (err) {\n 101:\t\t\tif (err != -ENOENT) {\n 102:\t\t\t\tpr_err(\"failed to retrieve LUO state '%s' from KHO: %pe\\n\",\n 103:\t\t\t\t LUO_KHO_ENTRY_NAME, ERR_PTR(err));\n 104:\t\t\t\treturn err;\n 105:\t\t\t}\n 106:\t\n 107:\t\t\treturn 0;\n 108:\t\t}\n 109:\t\n 110:\t\tif (len \u003c sizeof(luo_ser)) {\n 111:\t\t\tpr_err(\"LUO state is too small (%zu \u003c %zu)\\n\", len, sizeof(*luo_ser));\n 112:\t\t\treturn -EINVAL;\n 113:\t\t}\n 114:\t\n 115:\t\tluo_ser = phys_to_virt(luo_ser_phys);\n 116:\t\tif (strncmp(luo_ser-\u003ecompatible, LUO_ABI_COMPATIBLE, LUO_ABI_COMPAT_LEN)) {\n 117:\t\t\tpr_err(\"LUO state is incompatible with '%s'\\n\", LUO_ABI_COMPATIBLE);\n 118:\t\t\treturn -EINVAL;\n 119:\t\t}\n 120:\t\n 121:\t\tluo_global.liveupdate_num = luo_ser-\u003eliveupdate_num;\n 122:\t\tpr_info(\"Retrieved live update data, liveupdate number: %lld\\n\",\n 123:\t\t\tluo_global.liveupdate_num);\n 124:\t\n 125:\t\terr = luo_session_setup_incoming(luo_ser-\u003esessions_pa);\n 126:\t\tif (err)\n 127:\t\t\tgoto out_free_ser;\n 128:\t\n 129:\t\tluo_flb_setup_incoming(luo_ser-\u003eflbs_pa);\n 130:\t\n 131:\t\terr = 0;\n 132:\t\n 133:\tout_free_ser:\n 134:\t\tkho_restore_free(luo_ser);\n" }
41/2	2026/10/26 02:27	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 41731 output: 39 thoughts: 14 Thoughts: Okay, here's my interpretation of what's happening and what I'd be thinking if I were in your shoes, an expert in the field, analyzing this code: Analyzing the Execution Point Alright, I'm zeroing in on line 134 – what's the immediate aftermath of that line? That's the key. I need to understand the state of the system at that exact point in the execution flow. I need to consider what variables have been modified, what functions have been called (if any, that's crucial), and what the expected next operation is. What's the context? Is this the end of a loop, a conditional block, a function call, or some other key decision point? More importantly, I need to understand why we're focusing here. Is there a suspected bug in the code, or are we simply attempting to optimize performance at this spot? Is this a critical piece of the algorithm we need to nail down? I need to analyze this from the top, to ensure that the code is fulfilling the expectations of the requirements.
42/2	2026/10/26 02:28	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 135, "LineCount": 40 } Results: { "Contents": " 135:\t\treturn err;\n 136:\t}\n 137:\t\n 138:\tstatic int __init liveupdate_early_init(void)\n 139:\t{\n 140:\t\tint err;\n 141:\t\n 142:\t\terr = luo_early_startup();\n 143:\t\tif (err) {\n 144:\t\t\tluo_global.enabled = false;\n 145:\t\t\tluo_restore_fail(\"The incoming tree failed to initialize properly [%pe], disabling live update\\n\",\n 146:\t\t\t\t\t ERR_PTR(err));\n 147:\t\t}\n 148:\t\n 149:\t\treturn err;\n 150:\t}\n 151:\tearly_initcall(liveupdate_early_init);\n 152:\t\n 153:\t/* Called during boot to create outgoing LUO state /\n 154:\tstatic int __init luo_state_setup(void)\n 155:\t{\n 156:\t\tstruct luo_ser luo_ser;\n 157:\t\tint err;\n 158:\t\n 159:\t\tluo_ser = kho_alloc_preserve(sizeof(luo_ser));\n 160:\t\tif (IS_ERR(luo_ser)) {\n 161:\t\t\tpr_err(\"failed to allocate/preserve LUO state memory\\n\");\n 162:\t\t\treturn PTR_ERR(luo_ser);\n 163:\t\t}\n 164:\t\n 165:\t\tstrscpy(luo_ser-\u003ecompatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser-\u003ecompatible));\n 166:\t\tluo_ser-\u003eliveupdate_num = luo_global.liveupdate_num + 1;\n 167:\t\n 168:\t\tluo_session_setup_outgoing(\u0026luo_ser-\u003esessions_pa);\n 169:\t\n 170:\t\terr = luo_flb_setup_outgoing(\u0026luo_ser-\u003eflbs_pa);\n 171:\t\tif (err)\n 172:\t\t\tgoto exit_free_luo_ser;\n 173:\t\n 174:\t\terr = kho_add_subtree(LUO_KHO_ENTRY_NAME, luo_ser, sizeof(luo_ser));\n" }
43/2	2026/10/26 02:28	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 42631 output: 39 thoughts: 27 Thoughts: Okay, let's dive into this. Investigating the `luo_late_startup` Function Right, so I need to understand this `luo_late_startup` function. Where is that defined? Ah, here we are, lines 190 to 210. Time to get a handle on what this bit of code is actually doing. Let's see if this is doing something critical or something easily understood.
44/2	2026/10/26 02:28	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 190, "LineCount": 25 } Results: { "Contents": " 190:\t * late initcall because it initializes the outgoing tree that is needed only\n 191:\t * once userspace starts using /dev/liveupdate.\n 192:\t /\n 193:\tstatic int __init luo_late_startup(void)\n 194:\t{\n 195:\t\tint err;\n 196:\t\n 197:\t\tif (!liveupdate_enabled())\n 198:\t\t\treturn 0;\n 199:\t\n 200:\t\terr = luo_state_setup();\n 201:\t\tif (err)\n 202:\t\t\tluo_global.enabled = false;\n 203:\t\n 204:\t\treturn err;\n 205:\t}\n 206:\tlate_initcall(luo_late_startup);\n 207:\t\n 208:\t/ Public Functions /\n 209:\t\n 210:\t/\n 211:\t liveupdate_reboot() - Kernel reboot notifier for live update final\n 212:\t * serialization.\n 213:\t \n 214:\t This function is invoked directly from the reboot() syscall pathway\n" }
45/2	2026/10/26 02:28	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43110 output: 39 thoughts: 441 Thoughts: My Analysis of the `/dev/liveupdate` Device Okay, let's break down how this `/dev/liveupdate` device works. First, I need to understand its initialization, specifically through `liveupdate_ioctl_init()`. It seems that `/dev/liveupdate` is created by `misc_register` only if `liveupdate_enabled()` returns true. And that, in turn, hinges on the `LIVEUPDATE` kernel configuration option being set, the kernel command line including `liveupdate=on`, and also that `KEXEC_HANDOVER` is enabled. But I need to be thorough. I should double-check the Kconfig options to confirm that those are the only conditions that enable it. Let me look over the configuration options. Right, `LIVEUPDATE` depends on `KEXEC_HANDOVER`, which further depends on architecture support for `KEXEC_HANDOVER` and `KEXEC_FILE`, and also selects `KEXEC_FILE`, `LIBFDT`, and `CMA`. There's also `KEXEC_HANDOVER_ENABLE_DEFAULT`, which defaults to enabling it if `KEXEC_HANDOVER` is enabled. That's good, confirms my understanding. Now, a key question: Does syzkaller test the `/dev/liveupdate` device? It appears so. From the crash reports or fuzzing results I've seen, syzkaller does open `/dev/liveupdate`, it then issues the `LIVEUPDATE_IOCTL_CREATE_SESSION` ioctl, obtains a session file descriptor, calls `LIVEUPDATE_SESSION_PRESERVE_FD` on a memfd created by `memfd_create`, and finally calls `LIVEUPDATE_SESSION_FREEZE`. This is a useful workflow to keep in mind, and also a good indicator of what I should be looking out for. A critical question is who can access `/dev/liveupdate`. It's a misc device, meaning any user-space process can open it. But, is access restricted somehow? I need to check the code that actually handles the ioctls, especially the access controls. Let me look at `kernel/liveupdate/luo_core.c`, specifically, line 425 to confirm whether it is root-only or not. That will be the deciding factor as to the vulnerability.
46/2	2026/10/26 02:28	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 415, "LineCount": 35 } Results: { "Contents": " 415:\t\n 416:\t\treturn op-\u003eexecute(\u0026ucmd);\n 417:\t}\n 418:\t\n 419:\tstatic const struct file_operations luo_fops = {\n 420:\t\t.owner\t\t= THIS_MODULE,\n 421:\t\t.open\t\t= luo_open,\n 422:\t\t.release\t= luo_release,\n 423:\t\t.unlocked_ioctl\t= luo_ioctl,\n 424:\t};\n 425:\t\n 426:\tstatic struct luo_device_state luo_dev = {\n 427:\t\t.miscdev = {\n 428:\t\t\t.minor = MISC_DYNAMIC_MINOR,\n 429:\t\t\t.name = \"liveupdate\",\n 430:\t\t\t.fops = \u0026luo_fops,\n 431:\t\t},\n 432:\t\t.in_use = ATOMIC_INIT(0),\n 433:\t};\n 434:\t\n 435:\tstatic int __init liveupdate_ioctl_init(void)\n 436:\t{\n 437:\t\tif (!liveupdate_enabled())\n 438:\t\t\treturn 0;\n 439:\t\n 440:\t\treturn misc_register(\u0026luo_dev.miscdev);\n 441:\t}\n 442:\tlate_initcall(liveupdate_ioctl_init);\n" }
47/2	2026/10/26 02:28	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44467 output: 39 thoughts: 11 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and rendered in the first person: Initial Assessment: Navigating the Landscape Alright, my first thought upon seeing that is immediately to zero in on `luo_open`. Given my expertise in [Insert relevant field, e.g., systems programming, data analysis, specific library or codebase], that identifier immediately triggers a series of associations. My intuition, based on the naming convention, is that `luo_open` likely represents a function, method, or potentially even a variable associated with opening, initializing, or accessing something. It's a gateway, a point of entry. It's essential that I understand its function and ensure I know what it actually does. So, I will proceed by checking the function definition.
48/2	2026/10/26 02:28	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 330, "LineCount": 35 } Results: { "Contents": " 330:\tstatic int luo_open(struct inode inodep, struct file filep)\n 331:\t{\n 332:\t\tstruct luo_device_state ldev = container_of(filep-\u003eprivate_data,\n 333:\t\t\t\t\t\t\t struct luo_device_state,\n 334:\t\t\t\t\t\t\t miscdev);\n 335:\t\n 336:\t\tif (atomic_cmpxchg(\u0026ldev-\u003ein_use, 0, 1))\n 337:\t\t\treturn -EBUSY;\n 338:\t\n 339:\t\t/ Always return -EIO to user if deserialization fail /\n 340:\t\tif (luo_session_deserialize()) {\n 341:\t\t\tatomic_set(\u0026ldev-\u003ein_use, 0);\n 342:\t\t\treturn -EIO;\n 343:\t\t}\n 344:\t\n 345:\t\treturn 0;\n 346:\t}\n 347:\t\n 348:\tstatic int luo_release(struct inode inodep, struct file filep)\n 349:\t{\n 350:\t\tstruct luo_device_state ldev = container_of(filep-\u003eprivate_data,\n 351:\t\t\t\t\t\t\t struct luo_device_state,\n 352:\t\t\t\t\t\t\t miscdev);\n 353:\t\tatomic_set(\u0026ldev-\u003ein_use, 0);\n 354:\t\n 355:\t\treturn 0;\n 356:\t}\n 357:\t\n 358:\tunion ucmd_buffer {\n 359:\t\tstruct liveupdate_ioctl_create_session create;\n 360:\t\tstruct liveupdate_ioctl_retrieve_session retrieve;\n 361:\t};\n 362:\t\n 363:\tstruct luo_ioctl_op {\n 364:\t\tunsigned int size;\n" }
49/2	2026/10/26 02:28	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 45192 output: 19 thoughts: 47 Thoughts: Okay, let's break this down. Investigating the `/dev/liveupdate` Potential Security Hole Right, so, the first thing that jumps out at me is `/dev/liveupdate`. Any process can open that, which immediately sets off alarm bells. That's a huge potential vulnerability! My initial reaction is, "Whoa, that's not good. That needs immediate scrutiny." But before I jump to conclusions, I need to understand the control flow. I need to figure out what happens when the system reboots. Specifically, does `liveupdate_reboot` get called during the `reboot()` process? If it does, then that `liveupdate_reboot` call is a key point to investigate. It's the intersection point. Therefore, I need to grep the codebase. I need to search for all instances of `liveupdate_reboot`. That should quickly reveal its call sites and give me context. This allows me to establish the execution paths and potential escalation vectors. This will tell me if the `/dev/liveupdate` endpoint has any security implications in the event of a reboot and, if so, the exact nature of the risk.
50/2	2026/10/26 02:28	tool	grepper	0m Args: { "Expression": "liveupdate_reboot" } Results: { "Output": "include/linux/liveupdate.h=234=bool liveupdate_enabled(void);\n--\ninclude/linux/liveupdate.h-236-/* Called during kexec to tell LUO that entered into reboot /\ninclude/linux/liveupdate.h:237:int liveupdate_reboot(void);\ninclude/linux/liveupdate.h-238-\n--\ninclude/linux/liveupdate.h=263=static inline bool liveupdate_enabled(void)\n--\ninclude/linux/liveupdate.h-267-\ninclude/linux/liveupdate.h:268:static inline int liveupdate_reboot(void)\ninclude/linux/liveupdate.h-269-{\n--\nkernel/kexec_core.c=1155=int kernel_kexec(void)\n--\nkernel/kexec_core.c-1166-\tif (!kexec_image-\u003epreserve_context) {\nkernel/kexec_core.c:1167:\t\terror = liveupdate_reboot();\nkernel/kexec_core.c-1168-\t\tif (error)\n--\nkernel/liveupdate/luo_core.c=206=late_initcall(luo_late_startup);\n--\nkernel/liveupdate/luo_core.c-210-/\nkernel/liveupdate/luo_core.c:211: liveupdate_reboot() - Kernel reboot notifier for live update final\nkernel/liveupdate/luo_core.c-212- * serialization.\n--\nkernel/liveupdate/luo_core.c-219- /\nkernel/liveupdate/luo_core.c:220:int liveupdate_reboot(void)\nkernel/liveupdate/luo_core.c-221-{\n--\nkernel/liveupdate/luo_file.c=427=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-470- \nkernel/liveupdate/luo_file.c:471: Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path.\nkernel/liveupdate/luo_file.c-472- * Return: 0 on success, or a negative errno on failure.\n--\nkernel/liveupdate/luo_flb.c=578=void __init luo_flb_setup_incoming(u64 flbs_pa)\n--\nkernel/liveupdate/luo_flb.c-602- \nkernel/liveupdate/luo_flb.c:603: Context: Called from liveupdate_reboot() just before kho_finalize().\nkernel/liveupdate/luo_flb.c-604- */\n" }
51/2	2026/10/26 02:28	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 46204 output: 24 thoughts: 1145 Thoughts: Reaching and Fuzzing LiveUpdate's Session Freezing Okay, so I've got this patch for LiveUpdate's session freezing, and my initial thought is, "Can I actually get to this code from a typical fuzzing environment?" Let's break it down. First, I see that `liveupdate_reboot()` calls `luo_session_serialize()`, which happens during a `reboot(LINUX_REBOOT_CMD_KEXEC)`. The patch adds `LIVEUPDATE_CMD_SESSION_FREEZE` and `LIVEUPDATE_SESSION_FREEZE` IOCTL, implements `luo_session_freeze()`, and then the key thing is all the checks around `session->user_frozen` within the session handling functions (`preserve_fd`, `freeze`, `serialize_one`, `unserialize_one`, and `release`). Basically, it prevents modifications or actions if a session is frozen. It looks like it is checking and controlling when to call `luo_file_freeze` and `luo_file_unfreeze`. The patch refactors file freezing by removing `file_set_ser` parameter because it's only used to set `count` and `files`. Now, the crucial question: can this code be executed in a standard setup, like GCE or QEMU? I have to go through the reachability gates. Based on the documentation, modifications are worth fuzzing if they can be executed. Looking at the documentation's criteria, it's pretty clear this is reachable code. LiveUpdate (LUO) is a core subsystem and there's a character device at `/dev/liveupdate`. It looks like I could use userspace to open the device, create sessions, preserve file descriptors, and call the freeze ioctl, and even trigger a kexec reboot to test the new functionality. So I can freeze the LUO session by calling the freeze ioctl, which prevents files from being preserved, etc. I have to check my architecture; I'm running on amd64. I need to check `ARCH_SUPPORTS_KEXEC_HANDOVER` and `ARCH_SUPPORTS_KEXEC_FILE` for amd64 to verify that kexec is supported. If that checks out, this path from userspace through the IOCTLs and towards a kexec reboot is open for fuzzing. This looks like reachable, executable code, so it's a "WorthFuzzing=true".
52/2	2026/10/26 02:28	tool	grepper	0m Args: { "Expression": "ARCH_SUPPORTS_KEXEC_HANDOVER" } Results: { "Output": "arch/arm64/Kconfig=1750=config ARCH_DEFAULT_KEXEC_IMAGE_VERIFY_SIG\n--\narch/arm64/Kconfig-1752-\narch/arm64/Kconfig:1753:config ARCH_SUPPORTS_KEXEC_HANDOVER\narch/arm64/Kconfig-1754-\tdef_bool y\n--\narch/x86/Kconfig=1974=config ARCH_SUPPORTS_KEXEC_JUMP\n--\narch/x86/Kconfig-1976-\narch/x86/Kconfig:1977:config ARCH_SUPPORTS_KEXEC_HANDOVER\narch/x86/Kconfig-1978-\tdef_bool X86_64\n--\nkernel/liveupdate/Kconfig=5=config KEXEC_HANDOVER\nkernel/liveupdate/Kconfig-6-\tbool \"kexec handover\"\nkernel/liveupdate/Kconfig:7:\tdepends on ARCH_SUPPORTS_KEXEC_HANDOVER \u0026\u0026 ARCH_SUPPORTS_KEXEC_FILE\nkernel/liveupdate/Kconfig-8-\tselect KEXEC_FILE\n" }
53/2	2026/10/26 02:28	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 48186 output: 39 thoughts: 1018 Thoughts: Analyzing Liveupdate Functionality in x86_64 Kernel Okay, so `x86_64` has `ARCH_SUPPORTS_KEXEC_HANDOVER` and `ARCH_SUPPORTS_KEXEC_FILE` enabled. That means `KEXEC_HANDOVER` is supported, which in turn enables `LIVEUPDATE`. And because `LIVEUPDATE` is on, `LIVEUPDATE_MEMFD` is also available, assuming the base dependencies are met: `MEMFD_CREATE` and `SHMEM`. That's the setup, good. Now, let's look at the actual code changes. I see several files have been modified: header files in `include/linux` and `include/uapi/linux`, core logic in `kernel/liveupdate`, and even `mm/memfd_luo.c` (though that's just a comment update, I'll keep that in mind). Also some changes in the `tools/testing/selftests/...` directory. The critical part is the new kernel functions. I want to understand what's been added: 1. `luo_session_freeze`: That's the ioctl handler for `LIVEUPDATE_SESSION_FREEZE`. This is important, it is the start of the freeze process. 2. `luo_file_freeze` and `luo_file_unfreeze`: These functions suggest a file-level freezing and unfreezing mechanism. Makes sense for a live update process. 3. `luo_session_serialize_one` and `luo_session_unserialize_one`: These are serialization/unserialization functions, likely for saving and restoring session state. 4. `luo_session_release`: This looks like the cleanup function for the liveupdate session after the update is completed. 5. `luo_session_preserve_fd`: This sounds interesting... it looks like it keeps some file descriptors alive across the update. 6. `luo_session_serialize`: Also serialization, likely for the whole session. Okay, now the visibility of these functions. Are these functions statically defined in the kernel? That impacts symbol table visibility. If these are in the symbol table, that makes them easier to be hooked. * `luo_session_freeze`: It's declared `static`, but because its address is taken (it's in a function pointer within `luo_session_ioctl_ops`), it won't be inlined and will have a symbol even with KALLSYMS. * `luo_file_freeze` and `luo_file_unfreeze`: Non-static, so definitely in the symbol table. * `luo_session_preserve_fd` is address-taken (in `luo_session_ioctl_ops`), symbol in vmlinux. * `luo_session_release` is address-taken (in `file_operations luo_session_fops`), Symbol in vmlinux! * `luo_session_serialize_one` is static. * `luo_session_serialize` is non-static. Now, let's examine `luo_session_fops` in `kernel/liveupdate/luo_session.c` for some more insights, let's inspect lines 440-520. I need to understand how these new functions integrate with the overall file operations structure and any related ioctls.
54/2	2026/10/26 02:29	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_session.c", "FirstLine": 440, "LineCount": 80 } Results: { "Contents": " 440:\t\t\t struct liveupdate_session_get_name, name, LUO_IOCTL_ALL),\n 441:\t\tIOCTL_OP(LIVEUPDATE_SESSION_FREEZE, luo_session_freeze,\n 442:\t\t\t struct liveupdate_session_freeze, reserved, LUO_IOCTL_OUTGOING),\n 443:\t};\n 444:\t\n 445:\tstatic bool luo_ioctl_type_valid(struct luo_session session,\n 446:\t\t\t\t\t const struct luo_ioctl_op op)\n 447:\t{\n 448:\t\tswitch (op-\u003etype) {\n 449:\t\tcase LUO_IOCTL_INCOMING:\n 450:\t\t\t/* Retrieved is only set on incoming sessions /\n 451:\t\t\treturn session-\u003eretrieved;\n 452:\t\tcase LUO_IOCTL_OUTGOING:\n 453:\t\t\treturn !session-\u003eretrieved;\n 454:\t\tcase LUO_IOCTL_ALL:\n 455:\t\t\treturn true;\n 456:\t\t}\n 457:\t\n 458:\t\t/ Catch-all. /\n 459:\t\treturn false;\n 460:\t}\n 461:\t\n 462:\tstatic long luo_session_ioctl(struct file filep, unsigned int cmd,\n 463:\t\t\t\t unsigned long arg)\n 464:\t{\n 465:\t\tstruct luo_session session = filep-\u003eprivate_data;\n 466:\t\tconst struct luo_ioctl_op op;\n 467:\t\tstruct luo_ucmd ucmd = {};\n 468:\t\tunion ucmd_buffer buf;\n 469:\t\tunsigned int nr;\n 470:\t\tint ret;\n 471:\t\n 472:\t\tnr = _IOC_NR(cmd);\n 473:\t\tif (nr \u003c LIVEUPDATE_CMD_SESSION_BASE \|\| (nr - LIVEUPDATE_CMD_SESSION_BASE) \u003e=\n 474:\t\t ARRAY_SIZE(luo_session_ioctl_ops)) {\n 475:\t\t\treturn -EINVAL;\n 476:\t\t}\n 477:\t\n 478:\t\tucmd.ubuffer = (void __user )arg;\n 479:\t\tret = get_user(ucmd.user_size, (u32 __user )ucmd.ubuffer);\n 480:\t\tif (ret)\n 481:\t\t\treturn ret;\n 482:\t\n 483:\t\top = \u0026luo_session_ioctl_ops[nr - LIVEUPDATE_CMD_SESSION_BASE];\n 484:\t\tif (op-\u003eioctl_num != cmd)\n 485:\t\t\treturn -ENOIOCTLCMD;\n 486:\t\tif (!luo_ioctl_type_valid(session, op))\n 487:\t\t\treturn -EINVAL;\n 488:\t\tif (ucmd.user_size \u003c op-\u003emin_size)\n 489:\t\t\treturn -EINVAL;\n 490:\t\n 491:\t\tucmd.cmd = \u0026buf;\n 492:\t\tret = copy_struct_from_user(ucmd.cmd, op-\u003esize, ucmd.ubuffer,\n 493:\t\t\t\t\t ucmd.user_size);\n 494:\t\tif (ret)\n 495:\t\t\treturn ret;\n 496:\t\n 497:\t\tguard(rwsem_read)(\u0026luo_session_serialize_rwsem);\n 498:\t\treturn op-\u003eexecute(session, \u0026ucmd);\n 499:\t}\n 500:\t\n 501:\tstatic const struct file_operations luo_session_fops = {\n 502:\t\t.owner = THIS_MODULE,\n 503:\t\t.release = luo_session_release,\n 504:\t\t.unlocked_ioctl = luo_session_ioctl,\n 505:\t};\n 506:\t\n 507:\t/* Create a \"struct file\" for session /\n 508:\tstatic int luo_session_getfile(struct luo_session session, struct file *filep)\n 509:\t{\n 510:\t\tchar name_buf[128];\n 511:\t\tstruct file file;\n 512:\t\n 513:\t\tlockdep_assert_held(\u0026session-\u003emutex);\n 514:\t\tsnprintf(name_buf, sizeof(name_buf), \"[luo_session] %s\", session-\u003ename);\n 515:\t\tfile = anon_inode_getfile(name_buf, \u0026luo_session_fops, session, O_RDWR);\n 516:\t\tif (IS_ERR(file))\n 517:\t\t\treturn PTR_ERR(file);\n 518:\t\n 519:\t\t*filep = file;\n" }
55/2	2026/10/26 02:29	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 51255 output: 25 thoughts: 441 Thoughts: Analyzing the Live Update Session Freeze Mechanism Okay, so I'm digging into this `LIVEUPDATE_SESSION_FREEZE` ioctl, and here's what I've got so far: the `anon_inode_getfile` function is creating the file descriptor, backed by `luo_session_fops`. When that ioctl gets called on the file descriptor, it's going to hit `luo_session_freeze(session, &ucmd)`. That's the core of what's happening. Now, let's nail down those kernel configuration requirements. I need to make sure this code is even compiled and, more importantly, reachable. Let's trace this back. Looking at `kernel/liveupdate/Makefile`, I see: ```makefile obj-$(CONFIG_LIVEUPDATE) += luo.o luo-y := luo_core.o luo_file.o luo_session.o luo_flb.o ``` So `luo_session.o` and `luo_file.o` are indeed compiled only if `CONFIG_LIVEUPDATE` is set. That's good. Now, in `kernel/liveupdate/Kconfig`, I see: ```kconfig config KEXEC_HANDOVER bool "kexec handover" depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE select KEXEC_FILE select LIBFDT select CMA ... config LIVEUPDATE bool "Live Update Orchestrator" depends on KEXEC_HANDOVER ``` Aha! `CONFIG_LIVEUPDATE` depends on `CONFIG_KEXEC_HANDOVER`. And, of course, to actually have file handlers to preserve and freeze: `CONFIG_LIVEUPDATE_MEMFD` (which depends on `CONFIG_LIVEUPDATE`, `CONFIG_MEMFD_CREATE`, `CONFIG_SHMEM`). Also, `CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT` is helpful because otherwise KHO needs the `kho=on` command line arg. I will have to remember that. Okay, let's distill this down to the bare essentials. What are the key config options we need enabled for this to work? Just strip the `CONFIG_` prefix. So: - `LIVEUPDATE` - `KEXEC_HANDOVER` However, let's not get ahead of ourselves. Let's do a complete search and check if there are other dependencies in Kconfig or Makefile. Let's check `kernel/Makefile`.
56/2	2026/10/26 02:29	tool	grepper	0m Args: { "Expression": "liveupdate", "PathPrefixes": [ "kernel/" ] } Results: { "Output": "\nFull output is too long, showing 200 out of 534 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (7 files in total):\nkernel/Makefile:1\nkernel/kexec_core.c:2\nkernel/liveupdate/luo_core.c:33\nkernel/liveupdate/luo_file.c:36\nkernel/liveupdate/luo_flb.c:42\nkernel/liveupdate/luo_internal.h:10\nkernel/liveupdate/luo_session.c:18\n\nkernel/Makefile=56=obj-y += livepatch/\nkernel/Makefile:57:obj-y += liveupdate/\nkernel/Makefile-58-obj-y += dma/\n--\nkernel/kexec_core.c-17-#include \u003clinux/list.h\u003e\nkernel/kexec_core.c:18:#include \u003clinux/liveupdate.h\u003e\nkernel/kexec_core.c-19-#include \u003clinux/highmem.h\u003e\n--\nkernel/kexec_core.c=1155=int kernel_kexec(void)\n--\nkernel/kexec_core.c-1166-\tif (!kexec_image-\u003epreserve_context) {\nkernel/kexec_core.c:1167:\t\terror = liveupdate_reboot();\nkernel/kexec_core.c-1168-\t\tif (error)\n--\nkernel/liveupdate/luo_core.c-40- * .. note::\nkernel/liveupdate/luo_core.c:41: * To enable LUO, boot the kernel with the ``liveupdate=on`` command line\nkernel/liveupdate/luo_core.c-42- * parameter.\n--\nkernel/liveupdate/luo_core.c-56-#include \u003clinux/kobject.h\u003e\nkernel/liveupdate/luo_core.c:57:#include \u003clinux/liveupdate.h\u003e\nkernel/liveupdate/luo_core.c-58-#include \u003clinux/miscdevice.h\u003e\n--\nkernel/liveupdate/luo_core.c=67=static struct {\n--\nkernel/liveupdate/luo_core.c-69-\tstruct luo_ser luo_ser_out;\nkernel/liveupdate/luo_core.c:70:\tu64 liveupdate_num;\nkernel/liveupdate/luo_core.c-71-} luo_global;\n--\nkernel/liveupdate/luo_core.c=76=DECLARE_RWSEM(luo_register_rwlock);\nkernel/liveupdate/luo_core.c-77-\nkernel/liveupdate/luo_core.c:78:static int __init early_liveupdate_param(char buf)\nkernel/liveupdate/luo_core.c-79-{\n--\nkernel/liveupdate/luo_core.c-81-}\nkernel/liveupdate/luo_core.c:82:early_param(\"liveupdate\", early_liveupdate_param);\nkernel/liveupdate/luo_core.c-83-\nkernel/liveupdate/luo_core.c=84=static int __init luo_early_startup(void)\n--\nkernel/liveupdate/luo_core.c-91-\tif (!kho_is_enabled()) {\nkernel/liveupdate/luo_core.c:92:\t\tif (liveupdate_enabled())\nkernel/liveupdate/luo_core.c:93:\t\t\tpr_warn(\"Disabling liveupdate because KHO is disabled\\n\");\nkernel/liveupdate/luo_core.c-94-\t\tluo_global.enabled = false;\n--\nkernel/liveupdate/luo_core.c-120-\nkernel/liveupdate/luo_core.c:121:\tluo_global.liveupdate_num = luo_ser-\u003eliveupdate_num;\nkernel/liveupdate/luo_core.c:122:\tpr_info(\"Retrieved live update data, liveupdate number: %lld\\n\",\nkernel/liveupdate/luo_core.c:123:\t\tluo_global.liveupdate_num);\nkernel/liveupdate/luo_core.c-124-\n--\nkernel/liveupdate/luo_core.c-137-\nkernel/liveupdate/luo_core.c:138:static int __init liveupdate_early_init(void)\nkernel/liveupdate/luo_core.c-139-{\n--\nkernel/liveupdate/luo_core.c-150-}\nkernel/liveupdate/luo_core.c:151:early_initcall(liveupdate_early_init);\nkernel/liveupdate/luo_core.c-152-\n--\nkernel/liveupdate/luo_core.c=154=static int __init luo_state_setup(void)\n--\nkernel/liveupdate/luo_core.c-165-\tstrscpy(luo_ser-\u003ecompatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser-\u003ecompatible));\nkernel/liveupdate/luo_core.c:166:\tluo_ser-\u003eliveupdate_num = luo_global.liveupdate_num + 1;\nkernel/liveupdate/luo_core.c-167-\n--\nkernel/liveupdate/luo_core.c-190- * late initcall because it initializes the outgoing tree that is needed only\nkernel/liveupdate/luo_core.c:191: * once userspace starts using /dev/liveupdate.\nkernel/liveupdate/luo_core.c-192- /\nkernel/liveupdate/luo_core.c=193=static int __init luo_late_startup(void)\n--\nkernel/liveupdate/luo_core.c-196-\nkernel/liveupdate/luo_core.c:197:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-198-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c=206=late_initcall(luo_late_startup);\n--\nkernel/liveupdate/luo_core.c-210-/\nkernel/liveupdate/luo_core.c:211: liveupdate_reboot() - Kernel reboot notifier for live update final\nkernel/liveupdate/luo_core.c-212- * serialization.\n--\nkernel/liveupdate/luo_core.c-219- /\nkernel/liveupdate/luo_core.c:220:int liveupdate_reboot(void)\nkernel/liveupdate/luo_core.c-221-{\n--\nkernel/liveupdate/luo_core.c-223-\nkernel/liveupdate/luo_core.c:224:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-225-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c-236-/\nkernel/liveupdate/luo_core.c:237: liveupdate_enabled - Check if the live update feature is enabled.\nkernel/liveupdate/luo_core.c-238- \nkernel/liveupdate/luo_core.c-239- This function returns the state of the live update feature flag, which\nkernel/liveupdate/luo_core.c:240: * can be controlled via the ``liveupdate`` kernel command-line parameter.\nkernel/liveupdate/luo_core.c-241- \n--\nkernel/liveupdate/luo_core.c-243- /\nkernel/liveupdate/luo_core.c:244:bool liveupdate_enabled(void)\nkernel/liveupdate/luo_core.c-245-{\n--\nkernel/liveupdate/luo_core.c-252- * The IOCTL user-space control interface for the LUO subsystem.\nkernel/liveupdate/luo_core.c:253: * It registers a character device, typically found at ``/dev/liveupdate``,\nkernel/liveupdate/luo_core.c-254- * which allows a userspace agent to manage the LUO state machine and its\n--\nkernel/liveupdate/luo_core.c-258- * to this device is exclusive: only one process is permitted to have\nkernel/liveupdate/luo_core.c:259: * ``/dev/liveupdate`` open at any given time. Subsequent open attempts will\nkernel/liveupdate/luo_core.c-260- * fail with -EBUSY until the first process closes its file descriptor.\n--\nkernel/liveupdate/luo_core.c=270=static int luo_ioctl_create_session(struct luo_ucmd ucmd)\nkernel/liveupdate/luo_core.c-271-{\nkernel/liveupdate/luo_core.c:272:\tstruct liveupdate_ioctl_create_session argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-273-\tstruct file file;\n--\nkernel/liveupdate/luo_core.c=300=static int luo_ioctl_retrieve_session(struct luo_ucmd ucmd)\nkernel/liveupdate/luo_core.c-301-{\nkernel/liveupdate/luo_core.c:302:\tstruct liveupdate_ioctl_retrieve_session argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-303-\tstruct file file;\n--\nkernel/liveupdate/luo_core.c=358=union ucmd_buffer {\nkernel/liveupdate/luo_core.c:359:\tstruct liveupdate_ioctl_create_session create;\nkernel/liveupdate/luo_core.c:360:\tstruct liveupdate_ioctl_retrieve_session retrieve;\nkernel/liveupdate/luo_core.c-361-};\n--\nkernel/liveupdate/luo_core.c=380=static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c-381-\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\nkernel/liveupdate/luo_core.c:382:\t\t struct liveupdate_ioctl_create_session, name),\nkernel/liveupdate/luo_core.c-383-\tIOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,\nkernel/liveupdate/luo_core.c:384:\t\t struct liveupdate_ioctl_retrieve_session, name),\nkernel/liveupdate/luo_core.c-385-};\n--\nkernel/liveupdate/luo_core.c=426=static struct luo_device_state luo_dev = {\n--\nkernel/liveupdate/luo_core.c-428-\t\t.minor = MISC_DYNAMIC_MINOR,\nkernel/liveupdate/luo_core.c:429:\t\t.name = \"liveupdate\",\nkernel/liveupdate/luo_core.c-430-\t\t.fops = \u0026luo_fops,\n--\nkernel/liveupdate/luo_core.c-434-\nkernel/liveupdate/luo_core.c:435:static int __init liveupdate_ioctl_init(void)\nkernel/liveupdate/luo_core.c-436-{\nkernel/liveupdate/luo_core.c:437:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-438-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c-441-}\nkernel/liveupdate/luo_core.c:442:late_initcall(liveupdate_ioctl_init);\n--\nkernel/liveupdate/luo_file.c-20- * Kernel modules responsible for a specific file type (e.g., memfd, vfio)\nkernel/liveupdate/luo_file.c:21: * register a \u0026struct liveupdate_file_handler. This handler provides a set of\nkernel/liveupdate/luo_file.c-22- * callbacks that LUO invokes at different stages of the update process, most\n--\nkernel/liveupdate/luo_file.c-57- * 3. Deserialize: After kexec, luo_file_deserialize() runs when session gets\nkernel/liveupdate/luo_file.c:58: * deserialized (which is when /dev/liveupdate is first opened). It reads the\nkernel/liveupdate/luo_file.c-59- * serialized data from the KHO memory region and reconstructs the in-memory\n--\nkernel/liveupdate/luo_file.c-124-#include \u003clinux/list_private.h\u003e\nkernel/liveupdate/luo_file.c:125:#include \u003clinux/liveupdate.h\u003e\nkernel/liveupdate/luo_file.c-126-#include \u003clinux/module.h\u003e\n--\nkernel/liveupdate/luo_file.c=136=static DEFINE_XARRAY(luo_preserved_files);\n--\nkernel/liveupdate/luo_file.c-139- * struct luo_file - Represents a single preserved file instance.\nkernel/liveupdate/luo_file.c:140: * @fh: Pointer to the \u0026struct liveupdate_file_handler that manages\nkernel/liveupdate/luo_file.c-141- * this type of file.\n--\nkernel/liveupdate/luo_file.c=178=struct luo_file {\nkernel/liveupdate/luo_file.c:179:\tstruct liveupdate_file_handler fh;\nkernel/liveupdate/luo_file.c-180-\tstruct file file;\n--\nkernel/liveupdate/luo_file.c-188-\nkernel/liveupdate/luo_file.c:189:static unsigned long luo_get_id(struct liveupdate_file_handler fh,\nkernel/liveupdate/luo_file.c-190-\t\t\t\tstruct file file)\n--\nkernel/liveupdate/luo_file.c=247=int luo_preserve_file(struct luo_file_set file_set, u64 token, int fd)\nkernel/liveupdate/luo_file.c-248-{\nkernel/liveupdate/luo_file.c:249:\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c:250:\tstruct liveupdate_file_handler fh;\nkernel/liveupdate/luo_file.c-251-\tstruct luo_file luo_file;\n--\nkernel/liveupdate/luo_file.c=351=void luo_file_unpreserve_files(struct luo_file_set file_set)\n--\nkernel/liveupdate/luo_file.c-355-\twhile (!list_empty(\u0026file_set-\u003efiles_list)) {\nkernel/liveupdate/luo_file.c:356:\t\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-357-\n--\nkernel/liveupdate/luo_file.c=385=static int luo_file_freeze_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-392-\tif (luo_file-\u003efh-\u003eops-\u003efreeze) {\nkernel/liveupdate/luo_file.c:393:\t\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-394-\n--\nkernel/liveupdate/luo_file.c=409=static void luo_file_unfreeze_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-414-\tif (luo_file-\u003efh-\u003eops-\u003eunfreeze) {\nkernel/liveupdate/luo_file.c:415:\t\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c-416-\n--\nkernel/liveupdate/luo_file.c=427=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-470- \nkernel/liveupdate/luo_file.c:471: * Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path.\nkernel/liveupdate/luo_file.c-472- * Return: 0 on success, or a negative errno on failure.\n--\nkernel/liveupdate/luo_file.c=564=int luo_retrieve_file(struct luo_file_set *file_set, u64 token,\n--\n\n" }
57/2	2026/10/26 02:29	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56533 output: 214 thoughts: 1579 Thoughts: Focusing the Fuzzing Effort Alright, let's nail down the best approach for fuzzing this patch. First, I need to identify the key functions that represent the core changes and entry points, while avoiding ubiquitous functions. Based on Section 4 guidance, I have reviewed the patch. I've determined that `luo_session_freeze`, a new ioctl entry point, `luo_file_freeze` and `luo_file_unfreeze` are modified, along with the serialization functions `luo_session_serialize_one` and `luo_session_unserialize_one`, and finally the modified release logic in `luo_session_release` and `luo_session_preserve_fd`. These functions all seem specific to the Live Update Orchestrator (LUO) and its freeze/session handling. I am excluding `luo_session_serialize_one` and `luo_session_unserialize_one`, however, because they are called by `luo_session_serialize`. Now, I'm verifying that these function addresses can be extracted so that GCC won't inline them. `luo_session_freeze`, `luo_session_preserve_fd` are used as function pointers within the `luo_session_ioctl_ops` structure. This prevents inlining. `luo_file_freeze`, `luo_file_unfreeze` and `luo_session_serialize` are global functions, so they should be fine as well. Therefore, I've confirmed that `luo_session_freeze`, `luo_file_freeze`, `luo_file_unfreeze`, `luo_session_preserve_fd`, and `luo_session_serialize` are good focus symbols. I have reviewed the relevant Kconfig options and confirm that enabling `LIVEUPDATE`, `KEXEC_HANDOVER`, `LIVEUPDATE_MEMFD`, and `KEXEC_HANDOVER_ENABLE_DEFAULT` provides all the necessary configuration. This ensures the fuzzer will have the full context available. Finally, I've confirmed that this patch is indeed worth fuzzing. It changes core subsystem logic (LUO), modifies session state and file handling, involves serialization and error handling, and all interactions are kernel-space-based through a character device and file descriptors, so it satisfies a lot of critical criteria. So the parameters for `set-results` are finalized: * `WorthFuzzing`: true * `Reasoning`: The patch adds a new ioctl, modifies session state, and interacts with file handlers within the kernel LUO subsystem. * `FocusSymbols`: * `luo_session_freeze` * `luo_file_freeze` * `luo_file_unfreeze` * `luo_session_preserve_fd` * `luo_session_serialize` * `EnableConfigs`: * `LIVEUPDATE` * `KEXEC_HANDOVER` * `LIVEUPDATE_MEMFD` * `KEXEC_HANDOVER_ENABLE_DEFAULT` With this information, we can focus the fuzzing effectively.
58/2	2026/10/26 02:29	tool	set-results	0m Args: { "EnableConfigs": [ "LIVEUPDATE", "KEXEC_HANDOVER", "LIVEUPDATE_MEMFD", "KEXEC_HANDOVER_ENABLE_DEFAULT" ], "FocusSymbols": [ "luo_session_freeze", "luo_file_freeze", "luo_file_unfreeze", "luo_session_preserve_fd", "luo_session_serialize" ], "Reasoning": "The patch introduces the LIVEUPDATE_SESSION_FREEZE ioctl to the Live Update Orchestrator (LUO) subsystem. This allows userspace to explicitly freeze session files and serialize metadata before kexec reboot. The changes modify session state handling, error recovery/rollback paths, file handler freezing/unfreezing, and session release logic. The code is exposed via the /dev/liveupdate character device and session file descriptors, making it fully reachable and testable in virtualized environments without requiring specialized physical hardware.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "LIVEUPDATE", "KEXEC_HANDOVER", "LIVEUPDATE_MEMFD", "KEXEC_HANDOVER_ENABLE_DEFAULT" ], "FocusSymbols": [ "luo_session_freeze", "luo_file_freeze", "luo_file_unfreeze", "luo_session_preserve_fd", "luo_session_serialize" ], "Reasoning": "The patch introduces the LIVEUPDATE_SESSION_FREEZE ioctl to the Live Update Orchestrator (LUO) subsystem. This allows userspace to explicitly freeze session files and serialize metadata before kexec reboot. The changes modify session state handling, error recovery/rollback paths, file handler freezing/unfreezing, and session release logic. The code is exposed via the /dev/liveupdate character device and session file descriptors, making it fully reachable and testable in virtualized environments without requiring specialized physical hardware.", "WorthFuzzing": true }
59/1	2026/10/26 02:29	action	If	2m Args: { "WorthFuzzing": true } Results: null
60/2	2026/10/26 02:29	agent	kmsan-evaluator	2m Model: core Args: null Results: { "KMSANReasoning": "The patch introduces the `LIVEUPDATE_SESSION_FREEZE` ioctl, allowing userspace to explicitly freeze a live-update session before kexec reboot.\n\nFrom a memory initialization and info-leak standpoint:\n1. User-kernel interface: The new ioctl parameter structure `struct liveupdate_session_freeze` consists of two `__u32` fields (`size` and `reserved`) with no structure padding (8 bytes total). In `luo_session_ioctl()`, input is copied and validated using `copy_struct_from_user()`, which zeroes any uncopied bytes within the kernel size. The ioctl response via `luo_ucmd_respond()` copies back the struct without exposing uninitialized stack or heap bytes.\n2. Internal state and structures: `struct luo_session` is allocated via `kzalloc_obj()`, ensuring the newly added `bool user_frozen` field is initialized to false. KHO serialization buffers are allocated using `kho_alloc_preserve()`, which zeroes allocated memory.\n3. Bug surface: The primary risks associated with this patch involve session state transitions, lifecycle management (freeze/unfreeze on error/release), concurrency (guarded by mutex and rwsem), or error handling logic. Such bugs (e.g. use-after-free, double free, locking anomalies) are fully covered by KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nBecause no uninitialized memory reads or information leak hazards are introduced, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 0756a3f342510e16a8b645b5dd51139b212e6a81 Author: syz-cluster <triage@syzkaller.com> Date: Mon Oct 26 02:25:46 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h index 6051abc0612ce..851692571e130 100644 --- a/include/linux/liveupdate.h +++ b/include/linux/liveupdate.h @@ -59,7 +59,8 @@ struct liveupdate_file_op_args { * compatible with the given file. * @preserve: Required. Performs state-saving for the file. * @unpreserve: Required. Cleans up any resources allocated by @preserve. - * @freeze: Optional. Final actions just before kernel transition. + * @freeze: Optional. Prepares final state before kexec (via + * LIVEUPDATE_SESSION_FREEZE or during reboot). * @unfreeze: Optional. Undo freeze operations. * @retrieve: Required. Restores the file in the new kernel. * @can_finish: Optional. Check if this FD can finish, i.e. all restoration diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h index 4043d40387125..3fb0cae0f7112 100644 --- a/include/uapi/linux/liveupdate.h +++ b/include/uapi/linux/liveupdate.h @@ -60,6 +60,7 @@ enum { LIVEUPDATE_CMD_SESSION_RETRIEVE_FD = 0x41, LIVEUPDATE_CMD_SESSION_FINISH = 0x42, LIVEUPDATE_CMD_SESSION_GET_NAME = 0x43, + LIVEUPDATE_CMD_SESSION_FREEZE = 0x44, }; / @@ -236,4 +237,28 @@ struct liveupdate_session_get_name { #define LIVEUPDATE_SESSION_GET_NAME \ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_NAME) +/ + * struct liveupdate_session_freeze - ioctl(LIVEUPDATE_SESSION_FREEZE) + * @size: Input; sizeof(struct liveupdate_session_freeze) + * @reserved: Input; Must be zero. Reserved for future use. + * + * Freezes the session from userspace before the kexec reboot phase. + * + * When this ioctl is called, the kernel executes the .freeze() callback on all + * preserved files in the session and serializes their metadata. Once frozen, + * no further files can be preserved in the session. + * + * During the subsequent kexec reboot, this session is recognized as already + * frozen and is skipped from the late auto freeze. + * + * Return: 0 on success, negative error code on failure. + / +struct liveupdate_session_freeze { + __u32 size; + __u32 reserved; +}; + +#define LIVEUPDATE_SESSION_FREEZE \ + _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_FREEZE) + #endif / _UAPI_LIVEUPDATE_H / diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c index a39992da504fb..fac2e5a6bdc06 100644 --- a/kernel/liveupdate/luo_file.c +++ b/kernel/liveupdate/luo_file.c @@ -31,9 +31,9 @@ - unpreserve(): Cleans up any resources allocated by .preserve(), called * if the preservation process is aborted before the reboot (i.e. session is * closed). - * - freeze(): A final pre-reboot opportunity to prepare the state for kexec. - * We are already in reboot syscall, and therefore userspace cannot mutate - * the file anymore. + * - freeze(): Prepares the final state for kexec. Invoked either via + * the LIVEUPDATE_SESSION_FREEZE ioctl once userspace is done modifying + * the session's files, or during the reboot() syscall. * - unfreeze(): Undoes the actions of .freeze(), called if the live update * is aborted after the freeze phase. * - retrieve(): Reconstructs the file in the new kernel from the preserved @@ -48,7 +48,8 @@ * handler, calls its .preserve() operation, and creates an internal &struct * luo_file to track the live state. * - * 2. Freeze (Pre-Reboot): Just before the kexec, luo_file_freeze() is called. + * 2. Freeze (Pre-Reboot): Either explicitly via LIVEUPDATE_SESSION_FREEZE or + * just before the kexec during reboot(), luo_file_freeze() is called. * It iterates through all preserved files, calls their respective .freeze() * operation, and serializes their final metadata (compatible string, token, * and data handle) into a contiguous memory block for KHO. @@ -74,15 +75,16 @@ * * 1. Abort Before Reboot: If the userspace agent aborts the live update * process before calling reboot (e.g., by closing the session file - * descriptor), the session's release handler calls - * luo_file_unpreserve_files(). This invokes the .unpreserve() callback on - * all preserved files, ensuring all allocated resources are cleaned up and - * returning the system to a clean state. + * descriptor), the session's release handler unfreezes the files if the + * session was already frozen and calls luo_file_unpreserve_files(). This + * invokes the .unpreserve() callback on all preserved files, ensuring all + * allocated resources are cleaned up and returning the system to a clean + * state. * - * 2. Freeze Failure: During the reboot() syscall, if any handler's .freeze() - * op fails, the .unfreeze() op is invoked on all previously successful - * freezes to roll back their state. The reboot() syscall then returns an - * error to userspace, canceling the live update. + * 2. Freeze Failure: During LIVEUPDATE_SESSION_FREEZE or the reboot() syscall, + * if any handler's .freeze() op fails, the .unfreeze() op is invoked on all + * previously successful freezes to roll back their state, and an error is + * returned to userspace, canceling the live update if called from reboot(). * * 3. Finish Failure: In the new kernel, if a handler's .finish() op fails, * the luo_file_finish() operation is aborted. LUO retains ownership of @@ -440,12 +442,11 @@ static void __luo_file_unfreeze(struct luo_file_set file_set, /* * luo_file_freeze - Freezes all preserved files and serializes their metadata. - * @file_set: The file_set whose files are to be frozen. - * @file_set_ser: Where to put the serialized file_set. + * @file_set: The file_set whose files are to be frozen. * - * This function is called from the reboot() syscall path, just before the - * kernel transitions to the new image via kexec. Its purpose is to perform the - * final preparation and serialization of all preserved files in the file_set. + * This function is called from LIVEUPDATE_SESSION_FREEZE or from the reboot() + * syscall path. Its purpose is to perform the final preparation and + * serialization of all preserved files in the file_set. * * It iterates through each preserved file in FIFO order (the order of * preservation) and performs two main actions: @@ -457,22 +458,20 @@ static void __luo_file_unfreeze(struct luo_file_set file_set, * 2. Serializes Metadata: After a successful freeze, it copies the final file * metadata—the handler's compatible string, the user token, and the final - * private data handle—into the pre-allocated contiguous memory buffer - * (file_set->files) that will be handed over to the next kernel via KHO. + * private data handle—into the pre-allocated serialization blocks + * (file_set->block_set) that will be handed over to the next kernel via KHO. * * Error Handling (Rollback): * This function is atomic. If any handler's .freeze() operation fails, the - * entire live update is aborted. The __luo_file_unfreeze() helper is - * immediately called to invoke the .unfreeze() op on all files that were - * successfully frozen before the point of failure, rolling them back to a - * running state. The function then returns an error, causing the reboot() - * syscall to fail. + * __luo_file_unfreeze() helper is immediately called to invoke the .unfreeze() + * op on all files that were successfully frozen before the point of failure, + * rolling them back to an unfrozen state, and an error is returned to the + * caller, canceling the live update if called from the reboot() path. * - * Context: Called only from the liveupdate_reboot() path. + * Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path. * Return: 0 on success, or a negative errno on failure. / -int luo_file_freeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser) +int luo_file_freeze(struct luo_file_set file_set) { struct luo_file luo_file; struct kho_block_set_it it; @@ -506,9 +505,6 @@ int luo_file_freeze(struct luo_file_set file_set, file_ser->token = luo_file->token; } - file_set_ser->count = file_set->count; - file_set_ser->files = kho_block_set_head_pa(&file_set->block_set); - return 0; err_unfreeze: @@ -519,28 +515,25 @@ int luo_file_freeze(struct luo_file_set file_set, /* * luo_file_unfreeze - Unfreezes all files in a file_set and clear serialization - * @file_set: The file_set whose files are to be unfrozen. - * @file_set_ser: Serialized file_set. + * @file_set: The file_set whose files are to be unfrozen. * * This function rolls back the state of all files in a file_set after the - * freeze phase has begun but must be aborted. It is the counterpart to - * luo_file_freeze(). + * freeze phase has begun. It is the counterpart to luo_file_freeze(). * * It invokes the __luo_file_unfreeze() helper with a NULL argument, which - * signals the helper to iterate through all files in the file_set and call - * their respective .unfreeze() handler callbacks. + * signals the helper to iterate through all files in the file_set, call their + * respective .unfreeze() handler callbacks, and clear the serialized blocks. * * Context: This is called when the live update is aborted during - * the reboot() syscall, after luo_file_freeze() has been called. + * the reboot() syscall, after luo_file_freeze() has been called, + * or when an explicitly frozen session is released before kexec. / -void luo_file_unfreeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser) +void luo_file_unfreeze(struct luo_file_set file_set) { if (!file_set->count) return; __luo_file_unfreeze(file_set, NULL); - memset(file_set_ser, 0, sizeof(file_set_ser)); } /* diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h index dac6644bfb18a..381499e73d2ac 100644 --- a/kernel/liveupdate/luo_internal.h +++ b/kernel/liveupdate/luo_internal.h @@ -64,6 +64,8 @@ struct luo_file_set { * previous kernel) sessions. * @retrieved: A boolean flag indicating whether this session has been * retrieved by a consumer in the new kernel. + * @user_frozen: A boolean flag indicating whether this session has been + * frozen explicitly from userspace. * @file_set: A set of files that belong to this session. * @mutex: protects fields in the luo_session. / @@ -71,6 +73,7 @@ struct luo_session { char name[LIVEUPDATE_SESSION_NAME_LENGTH]; struct list_head list; bool retrieved; + bool user_frozen; struct luo_file_set file_set; struct mutex mutex; }; @@ -103,10 +106,8 @@ int luo_session_deserialize(void); int luo_preserve_file(struct luo_file_set file_set, u64 token, int fd); void luo_file_unpreserve_files(struct luo_file_set file_set); -int luo_file_freeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser); -void luo_file_unfreeze(struct luo_file_set file_set, - struct luo_file_set_ser file_set_ser); +int luo_file_freeze(struct luo_file_set file_set); +void luo_file_unfreeze(struct luo_file_set file_set); int luo_retrieve_file(struct luo_file_set file_set, u64 token, struct file *filep); int luo_file_finish(struct luo_file_set file_set); diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c index f48e9a4185f97..cce6d09280b3e 100644 --- a/kernel/liveupdate/luo_session.c +++ b/kernel/liveupdate/luo_session.c @@ -34,10 +34,11 @@ * 1. Creation: A userspace agent calls `luo_session_create()` to create a * new, empty session and receives a file descriptor for it. * - * 2. Serialization: When the `reboot(LINUX_REBOOT_CMD_KEXEC)` syscall is - * made, `luo_session_serialize()` is called. It iterates through all - * active sessions and writes their metadata into a memory area preserved - * by KHO. + * 2. Freeze / Serialization: Sessions may be frozen explicitly from userspace + * via `LIVEUPDATE_SESSION_FREEZE`. When the `reboot(LINUX_REBOOT_CMD_KEXEC)` + * syscall is made, `luo_session_serialize()` is called to freeze any + * remaining active sessions and write all session metadata into a memory + * area preserved by KHO. * * 3. Deserialization (in new kernel): After kexec, `luo_session_deserialize()` * runs, reading the serialized data and creating a list of `struct @@ -218,18 +219,38 @@ static int luo_session_finish_one(struct luo_session session) return luo_file_finish(&session->file_set); } -static void luo_session_unfreeze_one(struct luo_session session, - struct luo_session_ser ser) +static void luo_session_unserialize_one(struct luo_session session, + struct luo_session_ser ser) { guard(mutex)(&session->mutex); - luo_file_unfreeze(&session->file_set, &ser->file_set_ser); + / + * Only unfreeze sessions that were auto-frozen by + * luo_session_serialize_one(); sessions frozen explicitly by + * userspace stay frozen until the session FD is closed. + / + if (!session->user_frozen) + luo_file_unfreeze(&session->file_set); + memset(ser, 0, sizeof(ser)); } -static int luo_session_freeze_one(struct luo_session session, - struct luo_session_ser ser) +static int luo_session_serialize_one(struct luo_session session, + struct luo_session_ser ser) { + int err; + guard(mutex)(&session->mutex); - return luo_file_freeze(&session->file_set, &ser->file_set_ser); + if (!session->user_frozen) { + err = luo_file_freeze(&session->file_set); + if (err) + return err; + } + + strscpy(ser->name, session->name, sizeof(ser->name)); + ser->file_set_ser.count = session->file_set.count; + ser->file_set_ser.files = + kho_block_set_head_pa(&session->file_set.block_set); + + return 0; } static int luo_session_release(struct inode inodep, struct file filep) @@ -249,8 +270,11 @@ static int luo_session_release(struct inode inodep, struct file filep) } sh = &luo_session_global.incoming; } else { - scoped_guard(mutex, &session->mutex) + scoped_guard(mutex, &session->mutex) { + if (session->user_frozen) + luo_file_unfreeze(&session->file_set); luo_file_unpreserve_files(&session->file_set); + } sh = &luo_session_global.outgoing; } @@ -267,6 +291,9 @@ static int luo_session_preserve_fd(struct luo_session session, int err; guard(mutex)(&session->mutex); + if (session->user_frozen) + return -EBUSY; + err = luo_preserve_file(&session->file_set, argp->token, argp->fd); if (err) return err; @@ -340,11 +367,40 @@ static int luo_session_get_name(struct luo_session session, return luo_ucmd_respond(ucmd, sizeof(argp)); } +static int luo_session_freeze(struct luo_session session, + struct luo_ucmd ucmd) +{ + struct liveupdate_session_freeze argp = ucmd->cmd; + int err; + + if (argp->reserved) + return -EINVAL; + + guard(mutex)(&session->mutex); + if (session->user_frozen) + return -EBUSY; + + err = luo_file_freeze(&session->file_set); + if (err) + return err; + + err = luo_ucmd_respond(ucmd, sizeof(argp)); + if (err) { + luo_file_unfreeze(&session->file_set); + return err; + } + + session->user_frozen = true; + + return 0; +} + union ucmd_buffer { struct liveupdate_session_finish finish; struct liveupdate_session_preserve_fd preserve; struct liveupdate_session_retrieve_fd retrieve; struct liveupdate_session_get_name get_name; + struct liveupdate_session_freeze freeze; }; / Type of sessions the ioctl applies to. / @@ -382,6 +438,8 @@ static const struct luo_ioctl_op luo_session_ioctl_ops[] = { struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING), IOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name, struct liveupdate_session_get_name, name, LUO_IOCTL_ALL), + IOCTL_OP(LIVEUPDATE_SESSION_FREEZE, luo_session_freeze, + struct liveupdate_session_freeze, reserved, LUO_IOCTL_OUTGOING), }; static bool luo_ioctl_type_valid(struct luo_session session, @@ -656,13 +714,11 @@ int luo_session_serialize(void) goto err_undo; } - err = luo_session_freeze_one(session, ser); + err = luo_session_serialize_one(session, ser); if (err) { kho_block_set_it_prev(&it); goto err_undo; } - - strscpy(ser->name, session->name, sizeof(ser->name)); } if (sh->count > 0) @@ -675,8 +731,7 @@ int luo_session_serialize(void) list_for_each_entry_continue_reverse(session, &sh->list, list) { struct luo_session_ser ser = kho_block_set_it_prev(&it); - luo_session_unfreeze_one(session, ser); - memset(ser->name, 0, sizeof(ser->name)); + luo_session_unserialize_one(session, ser); } up_write(&sh->rwsem); up_write(&luo_session_serialize_rwsem); diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c index 6b68220275ebe..a3bf872b3a03f 100644 --- a/mm/memfd_luo.c +++ b/mm/memfd_luo.c @@ -43,8 +43,9 @@ allocating pages for them during preservation. * * File Position - * The current file position is preserved, allowing applications to continue - * reading/writing from their last position. + * The file position at the time the session is frozen is preserved, + * allowing applications to continue reading/writing from their last + * position. * * File Status Flags * memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property diff --git a/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h b/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h index fa07fed083646..15a7db3a6b3e8 100644 --- a/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h +++ b/tools/testing/selftests/liveupdate/lib/include/libliveupdate.h @@ -26,6 +26,7 @@ int luo_create_session(int luo_fd, const char name); int luo_retrieve_session(int luo_fd, const char name); int luo_session_finish(int session_fd); int luo_get_session_name(int session_fd, char name, size_t name_len); +int luo_session_freeze(int session_fd); int luo_ensure_nofile_limit(long min_limit); int luo_session_preserve_fd(int session_fd, int fd, __u64 token); diff --git a/tools/testing/selftests/liveupdate/lib/lu_utils.c b/tools/testing/selftests/liveupdate/lib/lu_utils.c index 74d41115c2815..6315746ff08f8 100644 --- a/tools/testing/selftests/liveupdate/lib/lu_utils.c +++ b/tools/testing/selftests/liveupdate/lib/lu_utils.c @@ -198,6 +198,16 @@ int luo_session_finish(int session_fd) return 0; } +int luo_session_freeze(int session_fd) +{ + struct liveupdate_session_freeze arg = { .size = sizeof(arg) }; + + if (ioctl(session_fd, LIVEUPDATE_SESSION_FREEZE, &arg) < 0) + return -errno; + + return 0; +} + void create_state_file(int luo_fd, const char session_name, int token, int next_stage) { diff --git a/tools/testing/selftests/liveupdate/liveupdate.c b/tools/testing/selftests/liveupdate/liveupdate.c index 2dedd5fc2534f..c27f57eab8707 100644 --- a/tools/testing/selftests/liveupdate/liveupdate.c +++ b/tools/testing/selftests/liveupdate/liveupdate.c @@ -530,4 +530,49 @@ TEST_F(liveupdate_device, preserve_many_files) ASSERT_EQ(close(session_fd), 0); } +/* + * Test Case: Session Freeze + * + * Verifies the LIVEUPDATE_SESSION_FREEZE ioctl on an outgoing session. + / +TEST_F(liveupdate_device, session_freeze) +{ + struct liveupdate_session_freeze bad_arg = { + .size = sizeof(bad_arg), + .reserved = 1, + }; + int session_fd, mem_fd1, mem_fd2; + + self->fd1 = open(LIVEUPDATE_DEV, O_RDWR); + if (self->fd1 < 0 && errno == ENOENT) + SKIP(return, "%s does not exist", LIVEUPDATE_DEV); + ASSERT_GE(self->fd1, 0); + + session_fd = luo_create_session(self->fd1, "session-freeze-test"); + ASSERT_GE(session_fd, 0); + + mem_fd1 = memfd_create("freeze-memfd-1", 0); + ASSERT_GE(mem_fd1, 0); + ASSERT_EQ(luo_session_preserve_fd(session_fd, mem_fd1, 0x1111), 0); + + / Non-zero reserved field must fail with -EINVAL / + EXPECT_EQ(ioctl(session_fd, LIVEUPDATE_SESSION_FREEZE, &bad_arg), -1); + EXPECT_EQ(errno, EINVAL); + + / Freeze the session early / + ASSERT_EQ(luo_session_freeze(session_fd), 0); + + / Subsequent freeze attempt on an already frozen session must fail with -EBUSY / + EXPECT_EQ(luo_session_freeze(session_fd), -EBUSY); + + / Preserving a file after freeze must fail with -EBUSY */ + mem_fd2 = memfd_create("freeze-memfd-2", 0); + ASSERT_GE(mem_fd2, 0); + EXPECT_EQ(luo_session_preserve_fd(session_fd, mem_fd2, 0x2222), -EBUSY); + + ASSERT_EQ(close(session_fd), 0); + ASSERT_EQ(close(mem_fd1), 0); + ASSERT_EQ(close(mem_fd2), 0); +} + TEST_HARNESS_MAIN diff --git a/tools/testing/selftests/liveupdate/luo_kexec_simple.c b/tools/testing/selftests/liveupdate/luo_kexec_simple.c index 786ac93b9ae38..9bc8dab2e074c 100644 --- a/tools/testing/selftests/liveupdate/luo_kexec_simple.c +++ b/tools/testing/selftests/liveupdate/luo_kexec_simple.c @@ -40,6 +40,11 @@ static void run_stage_1(int luo_fd) TEST_MEMFD_TOKEN); } + ksft_print_msg("[STAGE 1] Freezing session '%s' early...\n", + TEST_SESSION_NAME); + if (luo_session_freeze(session_fd) < 0) + fail_exit("luo_session_freeze for '%s'", TEST_SESSION_NAME); + close(luo_fd); daemonize_and_wait(); } @@ -60,6 +65,9 @@ static void run_stage_2(int luo_fd, int state_session_fd) if (session_fd < 0) fail_exit("luo_retrieve_session for '%s'", TEST_SESSION_NAME); + if (luo_session_freeze(session_fd) != -EINVAL) + fail_exit("luo_session_freeze on incoming session did not return -EINVAL"); + ksft_print_msg("[STAGE 2] Restoring and verifying memfd (token %#x)...\n", TEST_MEMFD_TOKEN); mfd = restore_and_verify_memfd(session_fd, TEST_MEMFD_TOKEN,
61/3	2026/10/26 02:29	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 9717 output: 38 thoughts: 83 Thoughts: Here's my analysis of the patch, distilled into my current thinking: Examining a Liveupdate Subsystem Patch Okay, so this patch is introducing `LIVEUPDATE_SESSION_FREEZE` as a new ioctl within the `kernel/liveupdate/luo_session.c` module. My immediate thought is to consider the implications on the existing freeze, unfreeze, and serialization mechanisms within the liveupdate subsystem. I need to understand how this ioctl integrates and potentially modifies those processes. I want to carefully dissect the code changes to grasp the rationale behind this new functionality and its potential impact on the overall liveupdate workflow. My next move is to track down `luo_ucmd_respond` within the codebase, or whatever the common mechanism is for handling ioctl commands in the liveupdate subsystem. I need to understand how this new ioctl will be registered and processed. I'm going to follow the control flow to see how it interacts with the rest of the kernel. I’ll be looking for potential side effects and performance considerations that are introduced, especially regarding system state and resource locking.
62/3	2026/10/26 02:29	tool	grepper	0m Args: { "Expression": "luo_ucmd_respond\|IOCTL_OP", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_core.c=270=static int luo_ioctl_create_session(struct luo_ucmd ucmd)\n--\nkernel/liveupdate/luo_core.c-283-\nkernel/liveupdate/luo_core.c:284:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_core.c-285-\tif (err)\n--\nkernel/liveupdate/luo_core.c=300=static int luo_ioctl_retrieve_session(struct luo_ucmd ucmd)\n--\nkernel/liveupdate/luo_core.c-313-\nkernel/liveupdate/luo_core.c:314:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_core.c-315-\tif (err)\n--\nkernel/liveupdate/luo_core.c=363=struct luo_ioctl_op {\n--\nkernel/liveupdate/luo_core.c-369-\nkernel/liveupdate/luo_core.c:370:#define IOCTL_OP(_ioctl, _fn, _struct, _last) \\\nkernel/liveupdate/luo_core.c-371-\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_BASE] = { \\\n--\nkernel/liveupdate/luo_core.c=380=static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c:381:\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\nkernel/liveupdate/luo_core.c-382-\t\t struct liveupdate_ioctl_create_session, name),\nkernel/liveupdate/luo_core.c:383:\tIOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,\nkernel/liveupdate/luo_core.c-384-\t\t struct liveupdate_ioctl_retrieve_session, name),\n--\nkernel/liveupdate/luo_internal.h=15=struct luo_ucmd {\n--\nkernel/liveupdate/luo_internal.h-20-\nkernel/liveupdate/luo_internal.h:21:static inline int luo_ucmd_respond(struct luo_ucmd ucmd,\nkernel/liveupdate/luo_internal.h-22-\t\t\t\t size_t kernel_cmd_size)\n--\nkernel/liveupdate/luo_session.c=287=static int luo_session_preserve_fd(struct luo_session session,\n--\nkernel/liveupdate/luo_session.c-300-\nkernel/liveupdate/luo_session.c:301:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-302-\tif (err)\n--\nkernel/liveupdate/luo_session.c=308=static int luo_session_retrieve_fd(struct luo_session session,\n--\nkernel/liveupdate/luo_session.c-324-\nkernel/liveupdate/luo_session.c:325:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-326-\tif (err)\n--\nkernel/liveupdate/luo_session.c=341=static int luo_session_finish(struct luo_session session,\n--\nkernel/liveupdate/luo_session.c-353-\nkernel/liveupdate/luo_session.c:354:\treturn luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-355-}\n--\nkernel/liveupdate/luo_session.c=357=static int luo_session_get_name(struct luo_session session,\n--\nkernel/liveupdate/luo_session.c-366-\nkernel/liveupdate/luo_session.c:367:\treturn luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-368-}\n--\nkernel/liveupdate/luo_session.c=370=static int luo_session_freeze(struct luo_session session,\n--\nkernel/liveupdate/luo_session.c-386-\nkernel/liveupdate/luo_session.c:387:\terr = luo_ucmd_respond(ucmd, sizeof(*argp));\nkernel/liveupdate/luo_session.c-388-\tif (err) {\n--\nkernel/liveupdate/luo_session.c=413=struct luo_ioctl_op {\n--\nkernel/liveupdate/luo_session.c-420-\nkernel/liveupdate/luo_session.c:421:#define IOCTL_OP(_ioctl, _fn, _struct, _last, _type) \\\nkernel/liveupdate/luo_session.c-422-\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_SESSION_BASE] = { \\\n--\nkernel/liveupdate/luo_session.c=432=static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\nkernel/liveupdate/luo_session.c:433:\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\nkernel/liveupdate/luo_session.c-434-\t\t struct liveupdate_session_finish, reserved, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:435:\tIOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,\nkernel/liveupdate/luo_session.c-436-\t\t struct liveupdate_session_preserve_fd, token, LUO_IOCTL_OUTGOING),\nkernel/liveupdate/luo_session.c:437:\tIOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,\nkernel/liveupdate/luo_session.c-438-\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:439:\tIOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,\nkernel/liveupdate/luo_session.c-440-\t\t struct liveupdate_session_get_name, name, LUO_IOCTL_ALL),\nkernel/liveupdate/luo_session.c:441:\tIOCTL_OP(LIVEUPDATE_SESSION_FREEZE, luo_session_freeze,\nkernel/liveupdate/luo_session.c-442-\t\t struct liveupdate_session_freeze, reserved, LUO_IOCTL_OUTGOING),\n" }
63/3	2026/10/26 02:29	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 11839 output: 38 thoughts: 44 Thoughts: Here's my take on the thought process, tailored for an expert audience: Diving into the Live Update Framework Alright, let's get down to brass tacks. I need to refresh my memory on the internal workings of the live update process. Specifically, I'm focusing on the communication flow – how user commands are initiated and responded to within the live update object (`luo`). Let's jump into `kernel/liveupdate/luo_internal.h`, around line 15, to drill into the details surrounding `luo_ucmd` and `luo_ucmd_respond`. This section should reveal the core mechanisms behind processing user commands and sending back the corresponding feedback. I'm looking for the structural elements: data structures, function prototypes, and any key macro definitions that define the input, output, and status. I need to clearly understand these fundamental components to accurately map user intentions to system-level actions.
64/3	2026/10/26 02:29	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_internal.h", "FirstLine": 10, "LineCount": 40 } Results: { "Contents": " 10:\t\n 11:\t#include \u003clinux/liveupdate.h\u003e\n 12:\t#include \u003clinux/uaccess.h\u003e\n 13:\t#include \u003clinux/kho_block.h\u003e\n 14:\t\n 15:\tstruct luo_ucmd {\n 16:\t\tvoid __user ubuffer;\n 17:\t\tu32 user_size;\n 18:\t\tvoid cmd;\n 19:\t};\n 20:\t\n 21:\tstatic inline int luo_ucmd_respond(struct luo_ucmd ucmd,\n 22:\t\t\t\t\t size_t kernel_cmd_size)\n 23:\t{\n 24:\t\t/\n 25:\t\t * Copy the minimum of what the user provided and what we actually\n 26:\t\t * have.\n 27:\t\t /\n 28:\t\tif (copy_to_user(ucmd-\u003eubuffer, ucmd-\u003ecmd,\n 29:\t\t\t\t min_t(size_t, ucmd-\u003euser_size, kernel_cmd_size))) {\n 30:\t\t\treturn -EFAULT;\n 31:\t\t}\n 32:\t\treturn 0;\n 33:\t}\n 34:\t\n 35:\t/\n 36:\t * Handles a deserialization failure: devices and memory is in unpredictable\n 37:\t * state.\n 38:\t \n 39:\t Continuing the boot process after a failure is dangerous because it could\n 40:\t * lead to leaks of private data.\n 41:\t /\n 42:\t#define luo_restore_fail(__fmt, ...) panic(__fmt, ##__VA_ARGS__)\n 43:\t\n 44:\t/\n 45:\t struct luo_file_set - A set of files that belong to the same sessions.\n 46:\t * @files_list: An ordered list of files associated with this session, it is\n 47:\t * ordered by preservation time.\n 48:\t * @block_set: The set of serialization blocks.\n 49:\t * @count: A counter tracking the number of files currently stored in the\n" }
65/3	2026/10/26 02:29	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 12668 output: 45 thoughts: 112 Thoughts: Analyzing the User Command Response Okay, so the `luo_ucmd_respond` function is pretty straightforward at first glance. It copies data. Specifically, it's taking a chunk of data from `ucmd->cmd` and putting it into `ucmd->ubuffer`. The size of this copy is limited by the minimum of three values: the size of the destination buffer, the user-provided size (`ucmd->user_size`), and the kernel command size (`kernel_cmd_size`). That tells me we've got some size limitations and a potential buffer copy, a classic place to look for vulnerabilities. Now, where does this `ucmd` structure actually get populated? I need to track the lifecycle of `ucmd` to understand where the size limits are imposed and how the data gets in there in the first place. So, I need to dig into the kernel code and look for where these ioctls are dispatched. Let's start with `kernel/liveupdate/luo_session.c`. I'm going to focus my search around `luo_session_ioctl` because that's the likely entry point. And I'll pay close attention to the `IOCTL_OP` macro or equivalent, which is likely where the actual ioctl commands are handled. That'll be my starting point for understanding how `ucmd` is set up and, consequently, understanding the overall behavior.
66/3	2026/10/26 02:29	tool	grepper	0m Args: { "Expression": "luo_ioctl_op\|luo_session_ioctl\|luo_ucmd", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_core.c=265=struct luo_device_state {\n--\nkernel/liveupdate/luo_core.c-269-\nkernel/liveupdate/luo_core.c:270:static int luo_ioctl_create_session(struct luo_ucmd ucmd)\nkernel/liveupdate/luo_core.c-271-{\n--\nkernel/liveupdate/luo_core.c-283-\nkernel/liveupdate/luo_core.c:284:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_core.c-285-\tif (err)\n--\nkernel/liveupdate/luo_core.c-299-\nkernel/liveupdate/luo_core.c:300:static int luo_ioctl_retrieve_session(struct luo_ucmd ucmd)\nkernel/liveupdate/luo_core.c-301-{\n--\nkernel/liveupdate/luo_core.c-313-\nkernel/liveupdate/luo_core.c:314:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_core.c-315-\tif (err)\n--\nkernel/liveupdate/luo_core.c=358=union ucmd_buffer {\n--\nkernel/liveupdate/luo_core.c-362-\nkernel/liveupdate/luo_core.c:363:struct luo_ioctl_op {\nkernel/liveupdate/luo_core.c-364-\tunsigned int size;\n--\nkernel/liveupdate/luo_core.c-366-\tunsigned int ioctl_num;\nkernel/liveupdate/luo_core.c:367:\tint (execute)(struct luo_ucmd ucmd);\nkernel/liveupdate/luo_core.c-368-};\n--\nkernel/liveupdate/luo_core.c-379-\nkernel/liveupdate/luo_core.c:380:static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c-381-\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\n--\nkernel/liveupdate/luo_core.c=387=static long luo_ioctl(struct file filep, unsigned int cmd, unsigned long arg)\nkernel/liveupdate/luo_core.c-388-{\nkernel/liveupdate/luo_core.c:389:\tconst struct luo_ioctl_op op;\nkernel/liveupdate/luo_core.c:390:\tstruct luo_ucmd ucmd = {};\nkernel/liveupdate/luo_core.c-391-\tunion ucmd_buffer buf;\n--\nkernel/liveupdate/luo_core.c-395-\tnr = _IOC_NR(cmd);\nkernel/liveupdate/luo_core.c:396:\tif (nr - LIVEUPDATE_CMD_BASE \u003e= ARRAY_SIZE(luo_ioctl_ops))\nkernel/liveupdate/luo_core.c-397-\t\treturn -EINVAL;\n--\nkernel/liveupdate/luo_core.c-403-\nkernel/liveupdate/luo_core.c:404:\top = \u0026luo_ioctl_ops[nr - LIVEUPDATE_CMD_BASE];\nkernel/liveupdate/luo_core.c-405-\tif (op-\u003eioctl_num != cmd)\n--\nkernel/liveupdate/luo_internal.h-14-\nkernel/liveupdate/luo_internal.h:15:struct luo_ucmd {\nkernel/liveupdate/luo_internal.h-16-\tvoid __user ubuffer;\n--\nkernel/liveupdate/luo_internal.h-20-\nkernel/liveupdate/luo_internal.h:21:static inline int luo_ucmd_respond(struct luo_ucmd ucmd,\nkernel/liveupdate/luo_internal.h-22-\t\t\t\t size_t kernel_cmd_size)\n--\nkernel/liveupdate/luo_session.c-62- * `luo_session_create()`, `luo_session_retrieve()`, `luo_session_release()`,\nkernel/liveupdate/luo_session.c:63: * and `luo_session_ioctl()`).\nkernel/liveupdate/luo_session.c-64- * - Writer: Taken by the serialization process (`luo_session_serialize()`)\n--\nkernel/liveupdate/luo_session.c=287=static int luo_session_preserve_fd(struct luo_session session,\nkernel/liveupdate/luo_session.c:288:\t\t\t\t struct luo_ucmd ucmd)\nkernel/liveupdate/luo_session.c-289-{\n--\nkernel/liveupdate/luo_session.c-300-\nkernel/liveupdate/luo_session.c:301:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-302-\tif (err)\n--\nkernel/liveupdate/luo_session.c=308=static int luo_session_retrieve_fd(struct luo_session session,\nkernel/liveupdate/luo_session.c:309:\t\t\t\t struct luo_ucmd ucmd)\nkernel/liveupdate/luo_session.c-310-{\n--\nkernel/liveupdate/luo_session.c-324-\nkernel/liveupdate/luo_session.c:325:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-326-\tif (err)\n--\nkernel/liveupdate/luo_session.c=341=static int luo_session_finish(struct luo_session session,\nkernel/liveupdate/luo_session.c:342:\t\t\t struct luo_ucmd ucmd)\nkernel/liveupdate/luo_session.c-343-{\n--\nkernel/liveupdate/luo_session.c-353-\nkernel/liveupdate/luo_session.c:354:\treturn luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-355-}\n--\nkernel/liveupdate/luo_session.c=357=static int luo_session_get_name(struct luo_session session,\nkernel/liveupdate/luo_session.c:358:\t\t\t\tstruct luo_ucmd ucmd)\nkernel/liveupdate/luo_session.c-359-{\n--\nkernel/liveupdate/luo_session.c-366-\nkernel/liveupdate/luo_session.c:367:\treturn luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-368-}\n--\nkernel/liveupdate/luo_session.c=370=static int luo_session_freeze(struct luo_session session,\nkernel/liveupdate/luo_session.c:371:\t\t\t struct luo_ucmd ucmd)\nkernel/liveupdate/luo_session.c-372-{\n--\nkernel/liveupdate/luo_session.c-386-\nkernel/liveupdate/luo_session.c:387:\terr = luo_ucmd_respond(ucmd, sizeof(argp));\nkernel/liveupdate/luo_session.c-388-\tif (err) {\n--\nkernel/liveupdate/luo_session.c=407=enum luo_ioctl_type {\n--\nkernel/liveupdate/luo_session.c-412-\nkernel/liveupdate/luo_session.c:413:struct luo_ioctl_op {\nkernel/liveupdate/luo_session.c-414-\tunsigned int size;\n--\nkernel/liveupdate/luo_session.c-417-\tenum luo_ioctl_type type;\nkernel/liveupdate/luo_session.c:418:\tint (execute)(struct luo_session session, struct luo_ucmd ucmd);\nkernel/liveupdate/luo_session.c-419-};\n--\nkernel/liveupdate/luo_session.c-431-\nkernel/liveupdate/luo_session.c:432:static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\nkernel/liveupdate/luo_session.c-433-\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\n--\nkernel/liveupdate/luo_session.c=445=static bool luo_ioctl_type_valid(struct luo_session session,\nkernel/liveupdate/luo_session.c:446:\t\t\t\t const struct luo_ioctl_op op)\nkernel/liveupdate/luo_session.c-447-{\n--\nkernel/liveupdate/luo_session.c-461-\nkernel/liveupdate/luo_session.c:462:static long luo_session_ioctl(struct file filep, unsigned int cmd,\nkernel/liveupdate/luo_session.c-463-\t\t\t unsigned long arg)\n--\nkernel/liveupdate/luo_session.c-465-\tstruct luo_session session = filep-\u003eprivate_data;\nkernel/liveupdate/luo_session.c:466:\tconst struct luo_ioctl_op *op;\nkernel/liveupdate/luo_session.c:467:\tstruct luo_ucmd ucmd = {};\nkernel/liveupdate/luo_session.c-468-\tunion ucmd_buffer buf;\n--\nkernel/liveupdate/luo_session.c-473-\tif (nr \u003c LIVEUPDATE_CMD_SESSION_BASE \|\| (nr - LIVEUPDATE_CMD_SESSION_BASE) \u003e=\nkernel/liveupdate/luo_session.c:474:\t ARRAY_SIZE(luo_session_ioctl_ops)) {\nkernel/liveupdate/luo_session.c-475-\t\treturn -EINVAL;\n--\nkernel/liveupdate/luo_session.c-482-\nkernel/liveupdate/luo_session.c:483:\top = \u0026luo_session_ioctl_ops[nr - LIVEUPDATE_CMD_SESSION_BASE];\nkernel/liveupdate/luo_session.c-484-\tif (op-\u003eioctl_num != cmd)\n--\nkernel/liveupdate/luo_session.c=501=static const struct file_operations luo_session_fops = {\n--\nkernel/liveupdate/luo_session.c-503-\t.release = luo_session_release,\nkernel/liveupdate/luo_session.c:504:\t.unlocked_ioctl = luo_session_ioctl,\nkernel/liveupdate/luo_session.c-505-};\n" }
67/3	2026/10/26 02:29	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15945 output: 39 thoughts: 26 Thoughts: Okay, here's my summary, taking on the persona you requested: Diving into `luo_session_ioctl` Alright, let's get down to brass tacks. I need to understand how the `luo_session_ioctl` function works. It looks like it's defined in `kernel/liveupdate/luo_session.c`, so that's where I'll start. It's an IOCTL handler, which means it’s how userspace interacts with this specific live update session functionality. I need to grasp how the userspace commands are interpreted and what the kernel side does in response. I'm assuming it handles things like starting, stopping, getting status, and maybe even pushing updates. This is crucial for figuring out the overall live update workflow, and how safely it's implemented. Time to delve into the code and see exactly what's happening under the hood. I expect to be able to identify its role in the system.
68/3	2026/10/26 02:29	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_session.c", "FirstLine": 460, "LineCount": 45 } Results: { "Contents": " 460:\t}\n 461:\t\n 462:\tstatic long luo_session_ioctl(struct file filep, unsigned int cmd,\n 463:\t\t\t\t unsigned long arg)\n 464:\t{\n 465:\t\tstruct luo_session session = filep-\u003eprivate_data;\n 466:\t\tconst struct luo_ioctl_op op;\n 467:\t\tstruct luo_ucmd ucmd = {};\n 468:\t\tunion ucmd_buffer buf;\n 469:\t\tunsigned int nr;\n 470:\t\tint ret;\n 471:\t\n 472:\t\tnr = _IOC_NR(cmd);\n 473:\t\tif (nr \u003c LIVEUPDATE_CMD_SESSION_BASE \|\| (nr - LIVEUPDATE_CMD_SESSION_BASE) \u003e=\n 474:\t\t ARRAY_SIZE(luo_session_ioctl_ops)) {\n 475:\t\t\treturn -EINVAL;\n 476:\t\t}\n 477:\t\n 478:\t\tucmd.ubuffer = (void __user )arg;\n 479:\t\tret = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);\n 480:\t\tif (ret)\n 481:\t\t\treturn ret;\n 482:\t\n 483:\t\top = \u0026luo_session_ioctl_ops[nr - LIVEUPDATE_CMD_SESSION_BASE];\n 484:\t\tif (op-\u003eioctl_num != cmd)\n 485:\t\t\treturn -ENOIOCTLCMD;\n 486:\t\tif (!luo_ioctl_type_valid(session, op))\n 487:\t\t\treturn -EINVAL;\n 488:\t\tif (ucmd.user_size \u003c op-\u003emin_size)\n 489:\t\t\treturn -EINVAL;\n 490:\t\n 491:\t\tucmd.cmd = \u0026buf;\n 492:\t\tret = copy_struct_from_user(ucmd.cmd, op-\u003esize, ucmd.ubuffer,\n 493:\t\t\t\t\t ucmd.user_size);\n 494:\t\tif (ret)\n 495:\t\t\treturn ret;\n 496:\t\n 497:\t\tguard(rwsem_read)(\u0026luo_session_serialize_rwsem);\n 498:\t\treturn op-\u003eexecute(session, \u0026ucmd);\n 499:\t}\n 500:\t\n 501:\tstatic const struct file_operations luo_session_fops = {\n 502:\t\t.owner = THIS_MODULE,\n 503:\t\t.release = luo_session_release,\n 504:\t\t.unlocked_ioctl = luo_session_ioctl,\n" }
69/3	2026/10/26 02:29	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16925 output: 39 thoughts: 137 Thoughts: Here's my analysis of the provided code snippet: Diving into `luo_session_ioctl` Okay, so I'm looking at the `luo_session_ioctl` function, specifically at how it handles user-provided data. The key section is this: ```c ucmd.cmd = &buf; ret = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer, ucmd.user_size); if (ret) return ret; ``` Right away, I see a call to `copy_struct_from_user`. My immediate thought is, "Ah, right, this is crucial. We're copying data from userspace into a kernel buffer." The first thing that jumps out is the potential for vulnerabilities here. Now, the documentation for `copy_struct_from_user` has to be checked, because the implications are huge. It zeroes trailing bytes up to `op->size` if `user_size < op->size`! This is great for avoiding information leaks, but I'm thinking, "how are we making sure we're getting the right `op->size`? Is it validated?" What the heck is `op`? That needs to be understood. Next, I need to understand what `IOCTL_OP` actually does. That's where the real logic is, so I'll need to go look at lines 415-445 of `luo_session.c` to see how this whole thing is structured. I need to understand the operation the IOCTL call is performing and how it is being used.
70/3	2026/10/26 02:29	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_session.c", "FirstLine": 410, "LineCount": 40 } Results: { "Contents": " 410:\t\tLUO_IOCTL_ALL,\n 411:\t};\n 412:\t\n 413:\tstruct luo_ioctl_op {\n 414:\t\tunsigned int size;\n 415:\t\tunsigned int min_size;\n 416:\t\tunsigned int ioctl_num;\n 417:\t\tenum luo_ioctl_type type;\n 418:\t\tint (execute)(struct luo_session session, struct luo_ucmd ucmd);\n 419:\t};\n 420:\t\n 421:\t#define IOCTL_OP(_ioctl, _fn, _struct, _last, _type) \\\n 422:\t\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_SESSION_BASE] = { \\\n 423:\t\t\t.size = sizeof(_struct) + \\\n 424:\t\t\t\tBUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) \u003c \\\n 425:\t\t\t\t\t\t sizeof(_struct)), \\\n 426:\t\t\t.min_size = offsetofend(_struct, _last), \\\n 427:\t\t\t.ioctl_num = _ioctl, \\\n 428:\t\t\t.type = _type, \\\n 429:\t\t\t.execute = _fn, \\\n 430:\t\t}\n 431:\t\n 432:\tstatic const struct luo_ioctl_op luo_session_ioctl_ops[] = {\n 433:\t\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\n 434:\t\t\t struct liveupdate_session_finish, reserved, LUO_IOCTL_INCOMING),\n 435:\t\tIOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,\n 436:\t\t\t struct liveupdate_session_preserve_fd, token, LUO_IOCTL_OUTGOING),\n 437:\t\tIOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,\n 438:\t\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),\n 439:\t\tIOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,\n 440:\t\t\t struct liveupdate_session_get_name, name, LUO_IOCTL_ALL),\n 441:\t\tIOCTL_OP(LIVEUPDATE_SESSION_FREEZE, luo_session_freeze,\n 442:\t\t\t struct liveupdate_session_freeze, reserved, LUO_IOCTL_OUTGOING),\n 443:\t};\n 444:\t\n 445:\tstatic bool luo_ioctl_type_valid(struct luo_session session,\n 446:\t\t\t\t\t const struct luo_ioctl_op *op)\n 447:\t{\n 448:\t\tswitch (op-\u003etype) {\n 449:\t\tcase LUO_IOCTL_INCOMING:\n" }
71/3	2026/10/26 02:29	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18231 output: 22 thoughts: 621 Thoughts: Analyzing a Potential Vulnerability in `luo_session_freeze` Okay, let's dissect this `luo_session_freeze` function. First, I see it's dealing with freezing a live update session. I'm checking the flow, starting with the arguments: `session` and `ucmd`. The interesting bit is this: `struct liveupdate_session_freeze argp = ucmd->cmd;`. `argp` is a pointer to a struct that's presumably populated from userspace. `copy_struct_from_user` seems to copy it from userspace. Then it calls `luo_ucmd_respond`. Now, the code checks `argp->reserved` and if it's set returns an error. The crucial step is the call to `luo_ucmd_respond(ucmd, sizeof(argp))`. The respond function copies from `ucmd->cmd` (which points to the user-provided data, and thus now contains data in `argp`) to `ucmd->ubuffer`. But what about the `struct liveupdate_session_freeze`? It has a `size` and `reserved` field, both 4 bytes, so a total of 8 bytes. `copy_struct_from_user` fills `argp`, but does `luo_session_freeze` modify it? No, it just checks the `reserved` field. And, it then responds with the user-provided data. Okay, now let's go back and examine the other function. I'm getting a nagging feeling. I'm focusing on the `ucmd_buffer buf;` in `luo_session_ioctl`, because that's where the buffer comes from. This `buf` is a local, uninitialized variable! My concern is that `copy_struct_from_user` does not zero the struct, only fills in the required size, and the rest is left as is. What happens with uninitialized data is undefined. This feels like an information leak. I should check how `copy_struct_from_user` works exactly by inspecting its implementation. Let's grep for it to see its behavior and confirm my suspicions!
72/3	2026/10/26 02:30	tool	grepper	0m Error: no matches Args: { "Expression": "int copy_struct_from_user" } Results: { "error": "no matches" }
73/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 19360 output: 41 thoughts: 29 Thoughts: Here's my thought process, as if I were thinking it: Locating the User-Space Structure Copy Function Alright, I need to track down the implementation of `copy_struct_from_user`. Given my experience, the logical place to start looking for a function dealing with user-space memory access and structure copying is going to be in either the `include/linux/uaccess.h` header file or potentially within the `lib/` directory of the kernel source. `uaccess.h` is the usual suspect for these kinds of macros and inline functions, as it's the standard place for core user/kernel memory manipulation primitives. However, sometimes these functions get tucked away into the `lib/` directory for code reuse. So, I will check both. It is a good practice to consult the source code and documentation.
74/3	2026/10/26 02:30	tool	grepper	0m Args: { "Expression": "copy_struct_from_user", "PathPrefixes": [ "include/linux/uaccess.h", "lib/" ] } Results: { "Output": "include/linux/uaccess.h=343=extern __must_check int check_zeroed_user(const void __user from, size_t size);\n--\ninclude/linux/uaccess.h-345-/\ninclude/linux/uaccess.h:346: copy_struct_from_user: copy a struct from userspace\ninclude/linux/uaccess.h-347- * @dst: Destination address, in kernel space. This buffer must be @ksize\n--\ninclude/linux/uaccess.h-371- \ninclude/linux/uaccess.h:372: err = copy_struct_from_user(\u0026karg, sizeof(karg), uarg, usize);\ninclude/linux/uaccess.h-373- * if (err)\n--\ninclude/linux/uaccess.h=392=static __always_inline __must_check int\ninclude/linux/uaccess.h:393:copy_struct_from_user(void dst, size_t ksize, const void __user src,\ninclude/linux/uaccess.h-394-\t\t size_t usize)\n--\ninclude/linux/uaccess.h=515=__copy_struct_generic_bounce_buffer(void dst, size_t dstsize,\n--\ninclude/linux/uaccess.h-532-/\ninclude/linux/uaccess.h:533: This is like copy_struct_from_user(), but the\ninclude/linux/uaccess.h-534- * src buffer was already copied into a kernel\n--\nlib/tests/usercopy_kunit.c=47=static void usercopy_test_check_nonzero_user(struct kunit test)\n--\nlib/tests/usercopy_kunit.c-104-\nlib/tests/usercopy_kunit.c:105:/ Test usage of copy_struct_from_user(). /\nlib/tests/usercopy_kunit.c:106:static void usercopy_test_copy_struct_from_user(struct kunit test)\nlib/tests/usercopy_kunit.c-107-{\n--\nlib/tests/usercopy_kunit.c-132-\tmemset(kmem, 0x0, size);\nlib/tests/usercopy_kunit.c:133:\tKUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,\nlib/tests/usercopy_kunit.c:134:\t\t \"copy_struct_from_user(usize == ksize) failed\");\nlib/tests/usercopy_kunit.c-135-\tKUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,\nlib/tests/usercopy_kunit.c:136:\t\t \"copy_struct_from_user(usize == ksize) gives unexpected copy\");\nlib/tests/usercopy_kunit.c-137-\n--\nlib/tests/usercopy_kunit.c-145-\tmemset(kmem, 0x0, size);\nlib/tests/usercopy_kunit.c:146:\tKUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,\nlib/tests/usercopy_kunit.c:147:\t\t \"copy_struct_from_user(usize \u003c ksize) failed\");\nlib/tests/usercopy_kunit.c-148-\tKUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,\nlib/tests/usercopy_kunit.c:149:\t\t \"copy_struct_from_user(usize \u003c ksize) gives unexpected copy\");\nlib/tests/usercopy_kunit.c-150-\n--\nlib/tests/usercopy_kunit.c-155-\tmemset(kmem, 0x0, size);\nlib/tests/usercopy_kunit.c:156:\tKUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), -E2BIG,\nlib/tests/usercopy_kunit.c:157:\t\t \"copy_struct_from_user(usize \u003e ksize) didn't give E2BIG\");\nlib/tests/usercopy_kunit.c-158-\n--\nlib/tests/usercopy_kunit.c-167-\tmemset(kmem, 0x0, size);\nlib/tests/usercopy_kunit.c:168:\tKUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,\nlib/tests/usercopy_kunit.c:169:\t\t \"copy_struct_from_user(usize \u003e ksize) failed\");\nlib/tests/usercopy_kunit.c-170-\tKUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,\nlib/tests/usercopy_kunit.c:171:\t\t \"copy_struct_from_user(usize \u003e ksize) gives unexpected copy\");\nlib/tests/usercopy_kunit.c-172-}\n--\nlib/tests/usercopy_kunit.c=319=static struct kunit_case usercopy_test_cases[] = {\n--\nlib/tests/usercopy_kunit.c-322-\tKUNIT_CASE(usercopy_test_check_nonzero_user),\nlib/tests/usercopy_kunit.c:323:\tKUNIT_CASE(usercopy_test_copy_struct_from_user),\nlib/tests/usercopy_kunit.c-324-\t{}\n" }
75/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21043 output: 36 thoughts: 31 Thoughts: Okay, let's dive into this. Here's my take on those thoughts, as if they're my own: Analyzing `copy_struct_from_user` in `include/linux/uaccess.h` Alright, time to get my hands dirty. I'm thinking I should start digging into the `copy_struct_from_user` function, and I'm zeroing in on line 390 in `include/linux/uaccess.h`. I need to refresh my memory on the details of this function. Let's see... it's a critical function for safely copying data structures from user space into the kernel. Considering it's in `uaccess.h`, it's almost certainly involved in handling the security aspects of the kernel user boundary. I'm guessing I'll find details on memory access checks, pointer validations, or some other aspects of preventing malicious userspace programs from corrupting kernel memory. I'll need to remember to look out for subtleties in how it handles alignment, potential race conditions, and how it deals with partial copies if the user-space buffer is smaller than the struct size. Let's get to it.
76/3	2026/10/26 02:30	tool	read-file	0m Args: { "File": "include/linux/uaccess.h", "FirstLine": 390, "LineCount": 40 } Results: { "Contents": " 390:\t * * -EFAULT: access to userspace failed.\n 391:\t /\n 392:\tstatic __always_inline __must_check int\n 393:\tcopy_struct_from_user(void dst, size_t ksize, const void __user src,\n 394:\t\t\t size_t usize)\n 395:\t{\n 396:\t\tsize_t size = min(ksize, usize);\n 397:\t\tsize_t rest = max(ksize, usize) - size;\n 398:\t\n 399:\t\t/ Double check if ksize is larger than a known object size. /\n 400:\t\tif (WARN_ON_ONCE(ksize \u003e __builtin_object_size(dst, 1)))\n 401:\t\t\treturn -E2BIG;\n 402:\t\n 403:\t\t/ Deal with trailing bytes. /\n 404:\t\tif (usize \u003c ksize) {\n 405:\t\t\tmemset(dst + size, 0, rest);\n 406:\t\t} else if (usize \u003e ksize) {\n 407:\t\t\tint ret = check_zeroed_user(src + size, rest);\n 408:\t\t\tif (ret \u003c= 0)\n 409:\t\t\t\treturn ret ?: -E2BIG;\n 410:\t\t}\n 411:\t\t/ Copy the interoperable parts of the struct. /\n 412:\t\tif (copy_from_user(dst, src, size))\n 413:\t\t\treturn -EFAULT;\n 414:\t\treturn 0;\n 415:\t}\n 416:\t\n 417:\t/\n 418:\t copy_struct_to_user: copy a struct to userspace\n 419:\t * @dst: Destination address, in userspace. This buffer must be @ksize\n 420:\t * bytes long.\n 421:\t * @usize: (Alleged) size of @dst struct.\n 422:\t * @src: Source address, in kernel space.\n 423:\t * @ksize: Size of @src struct.\n 424:\t * @ignored_trailing: Set to %true if there was a non-zero byte in @src that\n 425:\t * userspace cannot see because they are using an smaller struct.\n 426:\t \n 427:\t Copies a struct from kernel space to userspace, in a way that guarantees\n 428:\t * backwards-compatibility for struct syscall arguments (as long as future\n 429:\t * struct extensions are made such that all new fields are appended to the\n" }
77/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 22044 output: 39 thoughts: 968 Thoughts: Analyzing the Session Freeze Implementation Okay, let's break this down. I'm looking closely at the interaction between `luo_session_freeze`, `luo_ucmd_respond`, and the related `luo_session_ioctl` functions. Specifically, I'm trying to ensure the data flow and security of this session freeze operation. In `luo_session_ioctl`, the kernel processes an ioctl command. We have an operation `op` that's looked up by command number. There are checks for command validity and size constraints. The function then copies data from user space (`ucmd.ubuffer`) to a kernel buffer `buf` using `copy_struct_from_user`. A read lock on `luo_session_serialize_rwsem` is acquired, and the `execute` function for the `op` is called. Now, focusing on `luo_session_freeze`, which is one such `op`. The code validates a reserved field, acquires a mutex on the `session`, checks that the session isn't already frozen, and calls `luo_file_freeze`. After that, it calls `luo_ucmd_respond`, and if successful, sets the `user_frozen` flag to true. The key to understanding is `luo_ucmd_respond`. It does a `copy_to_user` from `ucmd->cmd` (which points to our kernel buffer `buf`) back to `ucmd->ubuffer` (which is in user space). Here's where it gets interesting: the code copies the minimum of what the user provided (`ucmd->user_size`) and the kernel command size (`kernel_cmd_size`), which is `sizeof(struct liveupdate_session_freeze)`. I had to double check the initialization process. In `luo_session_ioctl`, `copy_struct_from_user` copies the data from the user buffer into `buf`. If `ucmd->user_size` is less than `op->size`, the remaining bytes in `buf` are zeroed. However, in this specific case, `min_size` (the minimum size expected from the user) is equal to `sizeof(struct liveupdate_session_freeze)`. So, `copy_struct_from_user` either copies the entire struct, or does so while zeroing the remainder. Then, there's the question of what happens if the user provides more data than expected (i.e. if `ucmd->user_size > op->size`): `copy_struct_from_user` checks that the trailing user bytes are zero. `luo_ucmd_respond` only copies back the size of `op->size` (i.e. `sizeof(*argp)`) bytes, which ensures that only completely initialized data is passed back to user space. So, the data flow is: 1. User provides data via `ubuffer`. 2. `copy_struct_from_user` copies this to kernel `buf`, zeroing if necessary. 3. `luo_ucmd_respond` copies from `buf` back to user space `ubuffer`, truncating and only copying initialized data. Now, to make sure I haven't missed anything, I should probably check the related files: `luo_file.c`, `luo_session.c`, `luo_internal.h`, and `memfd_luo.c` around the freeze/unfreeze functions. Need to ensure there aren't any other data races or unexpected interactions with the file system.
78/3	2026/10/26 02:30	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_file.c", "FirstLine": 440, "LineCount": 85 } Results: { "Contents": " 440:\t\tkho_block_set_clear(\u0026file_set-\u003eblock_set);\n 441:\t}\n 442:\t\n 443:\t/*\n 444:\t luo_file_freeze - Freezes all preserved files and serializes their metadata.\n 445:\t * @file_set: The file_set whose files are to be frozen.\n 446:\t \n 447:\t This function is called from LIVEUPDATE_SESSION_FREEZE or from the reboot()\n 448:\t * syscall path. Its purpose is to perform the final preparation and\n 449:\t * serialization of all preserved files in the file_set.\n 450:\t \n 451:\t It iterates through each preserved file in FIFO order (the order of\n 452:\t * preservation) and performs two main actions:\n 453:\t \n 454:\t 1. Freezes the File: It calls the handler's .freeze() callback for each\n 455:\t * file. This gives the handler a final opportunity to quiesce the device or\n 456:\t * prepare its state for the upcoming reboot. The handler may update its\n 457:\t * private data handle during this step.\n 458:\t \n 459:\t 2. Serializes Metadata: After a successful freeze, it copies the final file\n 460:\t * metadata—the handler's compatible string, the user token, and the final\n 461:\t * private data handle—into the pre-allocated serialization blocks\n 462:\t * (file_set-\u003eblock_set) that will be handed over to the next kernel via KHO.\n 463:\t \n 464:\t Error Handling (Rollback):\n 465:\t * This function is atomic. If any handler's .freeze() operation fails, the\n 466:\t * __luo_file_unfreeze() helper is immediately called to invoke the .unfreeze()\n 467:\t * op on all files that were successfully frozen before the point of failure,\n 468:\t * rolling them back to an unfrozen state, and an error is returned to the\n 469:\t * caller, canceling the live update if called from the reboot() path.\n 470:\t \n 471:\t Context: Called from LIVEUPDATE_SESSION_FREEZE or the liveupdate_reboot() path.\n 472:\t * Return: 0 on success, or a negative errno on failure.\n 473:\t /\n 474:\tint luo_file_freeze(struct luo_file_set file_set)\n 475:\t{\n 476:\t\tstruct luo_file luo_file;\n 477:\t\tstruct kho_block_set_it it;\n 478:\t\tint err;\n 479:\t\n 480:\t\tif (!file_set-\u003ecount)\n 481:\t\t\treturn 0;\n 482:\t\n 483:\t\tkho_block_set_it_init(\u0026it, \u0026file_set-\u003eblock_set);\n 484:\t\n 485:\t\tlist_for_each_entry(luo_file, \u0026file_set-\u003efiles_list, list) {\n 486:\t\t\tstruct luo_file_ser file_ser = kho_block_set_it_reserve_entry(\u0026it);\n 487:\t\n 488:\t\t\t/* This should not fail normally as blocks were pre-allocated /\n 489:\t\t\tif (WARN_ON_ONCE(!file_ser)) {\n 490:\t\t\t\terr = -ENOSPC;\n 491:\t\t\t\tgoto err_unfreeze;\n 492:\t\t\t}\n 493:\t\n 494:\t\t\terr = luo_file_freeze_one(file_set, luo_file);\n 495:\t\t\tif (err \u003c 0) {\n 496:\t\t\t\tpr_warn(\"Freeze failed for token[%#0llx] handler[%s] err[%pe]\\n\",\n 497:\t\t\t\t\tluo_file-\u003etoken, luo_file-\u003efh-\u003ecompatible,\n 498:\t\t\t\t\tERR_PTR(err));\n 499:\t\t\t\tgoto err_unfreeze;\n 500:\t\t\t}\n 501:\t\n 502:\t\t\tstrscpy(file_ser-\u003ecompatible, luo_file-\u003efh-\u003ecompatible,\n 503:\t\t\t\tsizeof(file_ser-\u003ecompatible));\n 504:\t\t\tfile_ser-\u003edata = luo_file-\u003eserialized_data;\n 505:\t\t\tfile_ser-\u003etoken = luo_file-\u003etoken;\n 506:\t\t}\n 507:\t\n 508:\t\treturn 0;\n 509:\t\n 510:\terr_unfreeze:\n 511:\t\t__luo_file_unfreeze(file_set, luo_file);\n 512:\t\n 513:\t\treturn err;\n 514:\t}\n 515:\t\n 516:\t/\n 517:\t luo_file_unfreeze - Unfreezes all files in a file_set and clear serialization\n 518:\t * @file_set: The file_set whose files are to be unfrozen.\n 519:\t \n 520:\t This function rolls back the state of all files in a file_set after the\n 521:\t * freeze phase has begun. It is the counterpart to luo_file_freeze().\n 522:\t \n 523:\t It invokes the __luo_file_unfreeze() helper with a NULL argument, which\n 524:\t * signals the helper to iterate through all files in the file_set, call their\n" }
79/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25286 output: 32 thoughts: 686 Thoughts: Analyzing the Changes in Luo Session Serialization Okay, let's break down these changes. It looks like we've significantly altered how file sets are handled during session serialization and unserialization. Previously, in `luo_file_freeze`, we were directly copying `file_set` data into `file_set_ser` with this: ```c - file_set_ser->count = file_set->count; - file_set_ser->files = kho_block_set_head_pa(&file_set->block_set); ``` and clearing the `file_set_ser` on unfreeze: ```c - memset(file_set_ser, 0, sizeof(file_set_ser)); ``` Now, the populating of `file_set_ser` has moved to `luo_session_serialize_one`. Within this function, we have: ```c ser->file_set_ser.count = session->file_set.count; ser->file_set_ser.files = kho_block_set_head_pa(&session->file_set.block_set); ``` This change implies `luo_file_freeze` is no longer directly responsible for populating `file_set_ser` with the file set metadata, but just ensures the file set is ready for serialization. It looks like the freezing itself is managed by the `luo_session` struct and it's `user_frozen` field. `luo_session_unserialize_one` is interesting. The logic now only performs `luo_file_unfreeze` if `session->user_frozen` is false. This indicates a distinction between auto-frozen sessions and sessions frozen by the user. A key point is the check in `luo_session_release`. If the session is user-frozen, we also* unfreeze the file set. Also, it looks like `luo_file_unpreserve_files` is also called. The `luo_session_preserve_fd` function reinforces this. A user-frozen session prevents preservation. So, the introduction of `user_frozen` seems to be the linchpin. It dictates when we freeze/unfreeze and likely guides the memory management for these file sets during session lifecycle. Looks like the `luo_session` structure has been refactored to manage this freeze state now. We need to check how and where `struct luo_session` is actually allocated to get the full picture.
80/3	2026/10/26 02:30	tool	grepper	0m Args: { "Expression": "luo_session_create", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_core.c=270=static int luo_ioctl_create_session(struct luo_ucmd ucmd)\n--\nkernel/liveupdate/luo_core.c-279-\nkernel/liveupdate/luo_core.c:280:\terr = luo_session_create(argp-\u003ename, \u0026file);\nkernel/liveupdate/luo_core.c-281-\tif (err)\n--\nkernel/liveupdate/luo_internal.h=92=static inline struct luo_file_set luo_file_set_from_session_locked(struct liveupdate_session s)\n--\nkernel/liveupdate/luo_internal.h-99-\nkernel/liveupdate/luo_internal.h:100:int luo_session_create(const char name, struct file *filep);\nkernel/liveupdate/luo_internal.h-101-int luo_session_retrieve(const char name, struct file *filep);\n--\nkernel/liveupdate/luo_session.c-33- \nkernel/liveupdate/luo_session.c:34: * 1. Creation: A userspace agent calls `luo_session_create()` to create a\nkernel/liveupdate/luo_session.c-35- * new, empty session and receives a file descriptor for it.\n--\nkernel/liveupdate/luo_session.c-61- * - Readers: Taken by any path modifying or accessing session state (e.g.,\nkernel/liveupdate/luo_session.c:62: * `luo_session_create()`, `luo_session_retrieve()`, `luo_session_release()`,\nkernel/liveupdate/luo_session.c-63- * and `luo_session_ioctl()`).\n--\nkernel/liveupdate/luo_session.c=508=static int luo_session_getfile(struct luo_session session, struct file filep)\n--\nkernel/liveupdate/luo_session.c-523-\nkernel/liveupdate/luo_session.c:524:int luo_session_create(const char name, struct file **filep)\nkernel/liveupdate/luo_session.c-525-{\n" }
81/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27134 output: 39 thoughts: 26 Thoughts: Okay, let's dive into this. Here's my thought process on the matter, summarized as requested: Deconstructing `luo_session_create` Right, let's get down to brass tacks. I need to understand how these LiveUpdate sessions are actually created within the kernel. The goal is clear: dissect the `luo_session_create` function. I know it resides in `kernel/liveupdate/luo_session.c`, so that's the starting point. I'll need to understand the arguments it takes, the data structures it manipulates, and the overall flow of execution. I'm especially interested in any resource allocation and initialization that happens here; that's often where the critical bits reside. I'll be looking for potential race conditions or locking issues at this stage too, as it is the first stage. I'll be keeping an eye out for how this function interacts with other parts of the LiveUpdate framework. The underlying design is probably based on a state machine, so I'll be watching to see how the initial state is set up for a session. It's time to dive into the code and see what secrets it holds.
82/3	2026/10/26 02:30	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_session.c", "FirstLine": 520, "LineCount": 40 } Results: { "Contents": " 520:\t\n 521:\t\treturn 0;\n 522:\t}\n 523:\t\n 524:\tint luo_session_create(const char name, struct file filep)\n 525:\t{\n 526:\t\tsize_t len = strnlen(name, LIVEUPDATE_SESSION_NAME_LENGTH);\n 527:\t\tstruct luo_session session;\n 528:\t\tint err;\n 529:\t\n 530:\t\tif (len == 0 \|\| len \u003e LIVEUPDATE_SESSION_NAME_LENGTH - 1)\n 531:\t\t\treturn -EINVAL;\n 532:\t\n 533:\t\tsession = luo_session_alloc(name);\n 534:\t\tif (IS_ERR(session))\n 535:\t\t\treturn PTR_ERR(session);\n 536:\t\n 537:\t\tdown_read(\u0026luo_session_serialize_rwsem);\n 538:\t\terr = luo_session_insert(\u0026luo_session_global.outgoing, session);\n 539:\t\tif (err)\n 540:\t\t\tgoto err_free;\n 541:\t\n 542:\t\tmutex_lock(\u0026session-\u003emutex);\n 543:\t\terr = luo_session_getfile(session, filep);\n 544:\t\tmutex_unlock(\u0026session-\u003emutex);\n 545:\t\tif (err)\n 546:\t\t\tgoto err_remove;\n 547:\t\tup_read(\u0026luo_session_serialize_rwsem);\n 548:\t\n 549:\t\treturn 0;\n 550:\t\n 551:\terr_remove:\n 552:\t\tluo_session_remove(\u0026luo_session_global.outgoing, session);\n 553:\terr_free:\n 554:\t\tluo_session_free(session);\n 555:\t\tup_read(\u0026luo_session_serialize_rwsem);\n 556:\t\n 557:\t\treturn err;\n 558:\t}\n 559:\t\n" }
83/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28007 output: 32 thoughts: 12 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience and presented in the first person: Diving into `luo_session_alloc` Right, let's get down to brass tacks and take a closer look at `luo_session_alloc`. I need to understand its mechanics, how it behaves, and where it potentially bottlenecks or exposes vulnerabilities. Given the context of what we're working on, this is likely a critical function for managing... well, sessions, obviously! But the how is what I need to dig into. I'm wondering if it's thread-safe, how resource allocation is handled internally, and if there are any obvious race conditions that might be lurking. Time to start the deep dive and see what the code actually reveals. I want to look for potential flaws in error handling, and if there are memory leaks. Let's see how well it copes under load, and figure out the exact consequences if it fails.
84/3	2026/10/26 02:30	tool	grepper	0m Args: { "Expression": "luo_session_alloc", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_session.c=135=static struct luo_session_global luo_session_global = {\n--\nkernel/liveupdate/luo_session.c-149-\nkernel/liveupdate/luo_session.c:150:static struct luo_session luo_session_alloc(const char name)\nkernel/liveupdate/luo_session.c-151-{\n--\nkernel/liveupdate/luo_session.c=524=int luo_session_create(const char name, struct file filep)\n--\nkernel/liveupdate/luo_session.c-532-\nkernel/liveupdate/luo_session.c:533:\tsession = luo_session_alloc(name);\nkernel/liveupdate/luo_session.c-534-\tif (IS_ERR(session))\n--\nkernel/liveupdate/luo_session.c=612=static int luo_session_deserialize_one(struct luo_session_header sh,\n--\nkernel/liveupdate/luo_session.c-617-\nkernel/liveupdate/luo_session.c:618:\tsession = luo_session_alloc(ser-\u003ename);\nkernel/liveupdate/luo_session.c-619-\tif (IS_ERR(session)) {\n" }
85/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28606 output: 39 thoughts: 12 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, and delivered as a first-person summary: Diving into `luo_session_alloc` Alright, let's get down to brass tacks. I'm focusing in on `luo_session_alloc` now. I need to understand its behavior, its assumptions, and how it fits into the broader picture of session management in this Luo system. My immediate goal is to quickly grasp the allocation strategy. Is it using a simple pool, a more sophisticated memory management approach, or something entirely custom? I'm thinking about the potential failure modes right now. What happens if the allocation fails? Does it return a null pointer, throw an exception, or trigger some other form of error handling? More importantly, what's the graceful recovery path, if any? I'm anticipating potential concurrency issues as well. Is this function thread-safe? Are there any obvious race conditions that need further scrutiny, especially if this session allocation is heavily used. Furthermore, how does this function handle clean-up? Does it have a corresponding deallocation function? Are there any potential memory leaks if that deallocation function isn't called, or if it's called with incorrect arguments? What are the implications of the lifetime of a session? This is critical for assessing the overall system's stability. I need to see how the code handles resource constraints as well. What are the limits on session creation, and how are they enforced?
86/3	2026/10/26 02:30	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_session.c", "FirstLine": 148, "LineCount": 30 } Results: { "Contents": " 148:\t};\n 149:\t\n 150:\tstatic struct luo_session luo_session_alloc(const char name)\n 151:\t{\n 152:\t\tstruct luo_session session = kzalloc_obj(session);\n 153:\t\n 154:\t\tif (!session)\n 155:\t\t\treturn ERR_PTR(-ENOMEM);\n 156:\t\n 157:\t\tstrscpy(session-\u003ename, name, sizeof(session-\u003ename));\n 158:\t\tluo_file_set_init(\u0026session-\u003efile_set);\n 159:\t\tINIT_LIST_HEAD(\u0026session-\u003elist);\n 160:\t\tmutex_init(\u0026session-\u003emutex);\n 161:\t\n 162:\t\treturn session;\n 163:\t}\n 164:\t\n 165:\tstatic void luo_session_free(struct luo_session session)\n 166:\t{\n 167:\t\tluo_file_set_destroy(\u0026session-\u003efile_set);\n 168:\t\tmutex_destroy(\u0026session-\u003emutex);\n 169:\t\tkfree(session);\n 170:\t}\n 171:\t\n 172:\tstatic int luo_session_insert(struct luo_session_header sh,\n 173:\t\t\t\t struct luo_session session)\n 174:\t{\n 175:\t\tstruct luo_session it;\n 176:\t\tint err;\n 177:\t\n" }
87/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29383 output: 39 thoughts: 284 Thoughts: Analyzing the Session Serialization Logic Okay, so I'm looking at how `luo_session` objects are handled, and it seems like the memory for them is initially zeroed with `kzalloc_obj`, which means `user_frozen` starts at `false` (0). That's good to know. Now, I'm diving into the serialization process to understand how session data gets saved or transferred, focusing on `luo_session_serialize` and specifically `luo_session_serialize_one`. In this `luo_session_serialize_one` function, I see a mutex guard, which is standard for protecting shared data. And then, there's a conditional check: `if (!session->user_frozen)`. Ah, so if the session isn't already "frozen" by the user, the function calls `luo_file_freeze` on the `file_set`. This makes sense; we want to ensure data consistency before serialization, likely preventing any further modifications during the process. Then, the function copies the session name and populates the `file_set_ser` structure with the count and a pointer to the file set's block set. Seems straightforward. However, I'm pausing here. I need to understand how the `ser` structure, the target of this serialization, is actually allocated or passed to `luo_session_serialize_one`. Is it stack-allocated, dynamically allocated, or perhaps provided by the caller? This is a critical detail for memory management and potential race conditions. I need to see where `luo_session_serialize_one` is called and how the `ser` structure is handled. I need to shift my focus to lines 680-740 in `kernel/liveupdate/luo_session.c` to trace the allocation and usage of this `ser` structure, and see what I can learn.
88/3	2026/10/26 02:30	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_session.c", "FirstLine": 690, "LineCount": 55 } Results: { "Contents": " 690:\t\tkho_block_set_destroy(\u0026sh-\u003eblock_set);\n 691:\t\tsaved_err = err;\n 692:\t\treturn err;\n 693:\t}\n 694:\t\n 695:\tint luo_session_serialize(void)\n 696:\t{\n 697:\t\tstruct luo_session_header sh = \u0026luo_session_global.outgoing;\n 698:\t\tstruct luo_session session;\n 699:\t\tstruct kho_block_set_it it;\n 700:\t\tint err;\n 701:\t\n 702:\t\tdown_write(\u0026luo_session_serialize_rwsem);\n 703:\t\tdown_write(\u0026sh-\u003erwsem);\n 704:\t\tsh-\u003esessions_pa = 0;\n 705:\t\n 706:\t\tkho_block_set_it_init(\u0026it, \u0026sh-\u003eblock_set);\n 707:\t\n 708:\t\tlist_for_each_entry(session, \u0026sh-\u003elist, list) {\n 709:\t\t\tstruct luo_session_ser ser = kho_block_set_it_reserve_entry(\u0026it);\n 710:\t\n 711:\t\t\t/* This should not fail normally as blocks were pre-allocated /\n 712:\t\t\tif (WARN_ON_ONCE(!ser)) {\n 713:\t\t\t\terr = -ENOSPC;\n 714:\t\t\t\tgoto err_undo;\n 715:\t\t\t}\n 716:\t\n 717:\t\t\terr = luo_session_serialize_one(session, ser);\n 718:\t\t\tif (err) {\n 719:\t\t\t\tkho_block_set_it_prev(\u0026it);\n 720:\t\t\t\tgoto err_undo;\n 721:\t\t\t}\n 722:\t\t}\n 723:\t\n 724:\t\tif (sh-\u003ecount \u003e 0)\n 725:\t\t\tsh-\u003esessions_pa = kho_block_set_head_pa(\u0026sh-\u003eblock_set);\n 726:\t\tup_write(\u0026sh-\u003erwsem);\n 727:\t\n 728:\t\treturn 0;\n 729:\t\n 730:\terr_undo:\n 731:\t\tlist_for_each_entry_continue_reverse(session, \u0026sh-\u003elist, list) {\n 732:\t\t\tstruct luo_session_ser *ser = kho_block_set_it_prev(\u0026it);\n 733:\t\n 734:\t\t\tluo_session_unserialize_one(session, ser);\n 735:\t\t}\n 736:\t\tup_write(\u0026sh-\u003erwsem);\n 737:\t\tup_write(\u0026luo_session_serialize_rwsem);\n 738:\t\n 739:\t\treturn err;\n 740:\t}\n" }
89/3	2026/10/26 02:30	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30861 output: 29 thoughts: 658 Thoughts: Analyzing the Serialization Logic Okay, let's break down this `luo_session_serialize_one` function. My initial thought is to trace the flow and see where this optimization is heading. Previously, the serialization process was somewhat fragmented. We had `luo_session_freeze_one` which, in turn, called `luo_file_freeze`. Now, we're consolidating that. It seems we're moving the mutex guarding directly into `luo_session_serialize_one`, which makes sense for atomic operations. The key change is that if the session isn't user-frozen, we call `luo_file_freeze` directly. Then, we copy the name and directly populate `ser->file_set_ser.count` and `ser->file_set_ser.files` by grabbing these from the `session` struct. It looks cleaner this way. Now, inside `luo_file_freeze`, there's a loop through the `files_list`. The `kho_block_set_it_reserve_entry` method is used here to get the serializer entry. Within the loop, we call `luo_file_freeze_one`, copy compatible data, and serialize the token and data. It's good to see that serialization of each file is taken care of here. But wait a minute... I need to clarify something. Where are these blocks actually allocated for `file_set->block_set`? The code uses `kho_block_set_head_pa`, and I need to understand how `kho_block_set` works. Or how the blocks inside of `file_set->block_set` are initialized and allocated. That's a critical detail I need to verify to ensure this whole serialization process is consistent and memory safe. I'll need to go deeper into the `kho_block_set` implementation to understand the underlying allocation strategy.
90/3	2026/10/26 02:31	tool	grepper	0m Args: { "Expression": "block_set", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "\nFull output is too long, showing 200 out of 323 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (5 files in total):\nkernel/liveupdate/kexec_handover.c:1\nkernel/liveupdate/kho_block.c:34\nkernel/liveupdate/luo_file.c:18\nkernel/liveupdate/luo_internal.h:2\nkernel/liveupdate/luo_session.c:19\n\nkernel/liveupdate/kexec_handover.c=1966=void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,\n--\nkernel/liveupdate/kexec_handover.c-2033-\t /\nkernel/liveupdate/kexec_handover.c:2034:\tmemblock_set_kho_noprsrv_only();\nkernel/liveupdate/kexec_handover.c-2035-\n--\nkernel/liveupdate/kho_block.c-40-/\nkernel/liveupdate/kho_block.c:41: kho_block_set_init - Initialize a block set.\nkernel/liveupdate/kho_block.c-42- * @bs: The block set to initialize.\n--\nkernel/liveupdate/kho_block.c-44- /\nkernel/liveupdate/kho_block.c:45:void kho_block_set_init(struct kho_block_set bs, size_t entry_size)\nkernel/liveupdate/kho_block.c-46-{\nkernel/liveupdate/kho_block.c:47:\tbs = (struct kho_block_set)KHO_BLOCK_SET_INIT(bs, entry_size);\nkernel/liveupdate/kho_block.c-48-\tWARN_ON_ONCE(!bs-\u003ecount_per_block);\n--\nkernel/liveupdate/kho_block.c=52=static void kho_block_entries(struct kho_block block)\n--\nkernel/liveupdate/kho_block.c-57-/* Get the address of the serialized entry at the specified index /\nkernel/liveupdate/kho_block.c:58:static void kho_block_entry(struct kho_block_set_it it, u64 index)\nkernel/liveupdate/kho_block.c-59-{\n--\nkernel/liveupdate/kho_block.c-63-/ Free serialized data /\nkernel/liveupdate/kho_block.c:64:static void kho_block_free_ser(struct kho_block_set bs,\nkernel/liveupdate/kho_block.c-65-\t\t\t struct kho_block_header_ser ser)\n--\nkernel/liveupdate/kho_block.c-72-\nkernel/liveupdate/kho_block.c:73:static struct kho_block_header_ser kho_block_alloc_ser(struct kho_block_set bs)\nkernel/liveupdate/kho_block.c-74-{\n--\nkernel/liveupdate/kho_block.c-78-\nkernel/liveupdate/kho_block.c:79:static int kho_block_add(struct kho_block_set bs,\nkernel/liveupdate/kho_block.c-80-\t\t\t struct kho_block_header_ser ser)\n--\nkernel/liveupdate/kho_block.c-103-\nkernel/liveupdate/kho_block.c:104:static int kho_block_set_grow_one(struct kho_block_set bs)\nkernel/liveupdate/kho_block.c-105-{\n--\nkernel/liveupdate/kho_block.c-121-\nkernel/liveupdate/kho_block.c:122:static void kho_block_set_shrink_one(struct kho_block_set bs)\nkernel/liveupdate/kho_block.c-123-{\n--\nkernel/liveupdate/kho_block.c-142-/\nkernel/liveupdate/kho_block.c:143: kho_block_set_grow - Expand the block set to accommodate the target count.\nkernel/liveupdate/kho_block.c-144- * @bs: The block set.\n--\nkernel/liveupdate/kho_block.c-153- /\nkernel/liveupdate/kho_block.c:154:int kho_block_set_grow(struct kho_block_set bs, u64 count)\nkernel/liveupdate/kho_block.c-155-{\n--\nkernel/liveupdate/kho_block.c-162-\twhile (count \u003e bs-\u003enblocks * bs-\u003ecount_per_block) {\nkernel/liveupdate/kho_block.c:163:\t\terr = kho_block_set_grow_one(bs);\nkernel/liveupdate/kho_block.c-164-\t\tif (err)\n--\nkernel/liveupdate/kho_block.c-171-\twhile (bs-\u003enblocks \u003e orig_nblocks)\nkernel/liveupdate/kho_block.c:172:\t\tkho_block_set_shrink_one(bs);\nkernel/liveupdate/kho_block.c-173-\treturn err;\n--\nkernel/liveupdate/kho_block.c-176-/*\nkernel/liveupdate/kho_block.c:177: kho_block_set_shrink - Shrink the block set to accommodate the target count.\nkernel/liveupdate/kho_block.c-178- * @bs: The block set.\n--\nkernel/liveupdate/kho_block.c-191- /\nkernel/liveupdate/kho_block.c:192:void kho_block_set_shrink(struct kho_block_set bs, u64 count)\nkernel/liveupdate/kho_block.c-193-{\nkernel/liveupdate/kho_block.c-194-\twhile (bs-\u003enblocks \u003e 0 \u0026\u0026 count \u003c= (bs-\u003enblocks - 1) * bs-\u003ecount_per_block)\nkernel/liveupdate/kho_block.c:195:\t\tkho_block_set_shrink_one(bs);\nkernel/liveupdate/kho_block.c-196-}\n--\nkernel/liveupdate/kho_block.c-198-/\nkernel/liveupdate/kho_block.c:199: kho_block_set_is_cyclic - Check for cycles in a linked list of blocks.\nkernel/liveupdate/kho_block.c-200- * Uses Floyd's cycle-finding algorithm to ensure sanity of the incoming list.\n--\nkernel/liveupdate/kho_block.c-203- /\nkernel/liveupdate/kho_block.c:204:static bool kho_block_set_is_cyclic(struct kho_block_set bs)\nkernel/liveupdate/kho_block.c-205-{\n--\nkernel/liveupdate/kho_block.c-238-/*\nkernel/liveupdate/kho_block.c:239: kho_block_set_restore - Restore a block set from a physical address.\nkernel/liveupdate/kho_block.c-240- * @bs: The block set to restore.\n--\nkernel/liveupdate/kho_block.c-248- /\nkernel/liveupdate/kho_block.c:249:int kho_block_set_restore(struct kho_block_set bs, u64 head_pa)\nkernel/liveupdate/kho_block.c-250-{\n--\nkernel/liveupdate/kho_block.c-260-\tbs-\u003ehead_pa = head_pa;\nkernel/liveupdate/kho_block.c:261:\tif (kho_block_set_is_cyclic(bs)) {\nkernel/liveupdate/kho_block.c-262-\t\tbs-\u003ehead_pa = 0;\n--\nkernel/liveupdate/kho_block.c-282-err_destroy:\nkernel/liveupdate/kho_block.c:283:\tkho_block_set_destroy(bs);\nkernel/liveupdate/kho_block.c-284-\n--\nkernel/liveupdate/kho_block.c-295-/*\nkernel/liveupdate/kho_block.c:296: kho_block_set_destroy - Destroy all blocks in a block set.\nkernel/liveupdate/kho_block.c-297- * @bs: The block set.\nkernel/liveupdate/kho_block.c-298- /\nkernel/liveupdate/kho_block.c:299:void kho_block_set_destroy(struct kho_block_set bs)\nkernel/liveupdate/kho_block.c-300-{\n--\nkernel/liveupdate/kho_block.c-312-/*\nkernel/liveupdate/kho_block.c:313: kho_block_set_clear - Clear all serialized data in a block set.\nkernel/liveupdate/kho_block.c-314- * @bs: The block set to clear.\nkernel/liveupdate/kho_block.c-315- /\nkernel/liveupdate/kho_block.c:316:void kho_block_set_clear(struct kho_block_set bs)\nkernel/liveupdate/kho_block.c-317-{\n--\nkernel/liveupdate/kho_block.c-326-/*\nkernel/liveupdate/kho_block.c:327: kho_block_set_it_init - Initialize a block set iterator.\nkernel/liveupdate/kho_block.c-328- * @it: The iterator to initialize.\n--\nkernel/liveupdate/kho_block.c-330- /\nkernel/liveupdate/kho_block.c:331:void kho_block_set_it_init(struct kho_block_set_it it, struct kho_block_set bs)\nkernel/liveupdate/kho_block.c-332-{\n--\nkernel/liveupdate/kho_block.c-338-/\nkernel/liveupdate/kho_block.c:339: kho_block_set_it_reserve_entry - Reserve and return the next available slot for writing.\nkernel/liveupdate/kho_block.c-340- * @it: The block iterator.\n--\nkernel/liveupdate/kho_block.c-348- /\nkernel/liveupdate/kho_block.c:349:void kho_block_set_it_reserve_entry(struct kho_block_set_it it)\nkernel/liveupdate/kho_block.c-350-{\n--\nkernel/liveupdate/kho_block.c-368-/\nkernel/liveupdate/kho_block.c:369: kho_block_set_it_read_entry - Read the next serialized entry from the block set.\nkernel/liveupdate/kho_block.c-370- * @it: The block iterator.\n--\nkernel/liveupdate/kho_block.c-377- /\nkernel/liveupdate/kho_block.c:378:void kho_block_set_it_read_entry(struct kho_block_set_it it)\nkernel/liveupdate/kho_block.c-379-{\n--\nkernel/liveupdate/kho_block.c-393-/\nkernel/liveupdate/kho_block.c:394: kho_block_set_it_prev - Return the previous entry slot in the block set.\nkernel/liveupdate/kho_block.c-395- * @it: The block iterator.\n--\nkernel/liveupdate/kho_block.c-402- /\nkernel/liveupdate/kho_block.c:403:void kho_block_set_it_prev(struct kho_block_set_it it)\nkernel/liveupdate/kho_block.c-404-{\n--\nkernel/liveupdate/luo_file.c=247=int luo_preserve_file(struct luo_file_set file_set, u64 token, int fd)\n--\nkernel/liveupdate/luo_file.c-257-\nkernel/liveupdate/luo_file.c:258:\terr = kho_block_set_grow(\u0026file_set-\u003eblock_set, file_set-\u003ecount + 1);\nkernel/liveupdate/luo_file.c-259-\tif (err)\n--\nkernel/liveupdate/luo_file.c-327-err_shrink:\nkernel/liveupdate/luo_file.c:328:\tkho_block_set_shrink(\u0026file_set-\u003eblock_set, file_set-\u003ecount);\nkernel/liveupdate/luo_file.c-329-\n--\nkernel/liveupdate/luo_file.c=351=void luo_file_unpreserve_files(struct luo_file_set file_set)\n--\nkernel/liveupdate/luo_file.c-374-\t\tfile_set-\u003ecount--;\nkernel/liveupdate/luo_file.c:375:\t\tkho_block_set_shrink(\u0026file_set-\u003eblock_set, file_set-\u003ecount);\nkernel/liveupdate/luo_file.c-376-\n--\nkernel/liveupdate/luo_file.c-381-\nkernel/liveupdate/luo_file.c:382:\tkho_block_set_destroy(\u0026file_set-\u003eblock_set);\nkernel/liveupdate/luo_file.c-383-}\n--\nkernel/liveupdate/luo_file.c=427=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-439-\nkernel/liveupdate/luo_file.c:440:\tkho_block_set_clear(\u0026file_set-\u003eblock_set);\nkernel/liveupdate/luo_file.c-441-}\n--\nkernel/liveupdate/luo_file.c-461- * private data handle—into the pre-allocated serialization blocks\nkernel/liveupdate/luo_file.c:462: * (file_set-\u003eblock_set) that will be handed over to the next kernel via KHO.\nkernel/liveupdate/luo_file.c-463- \n--\nkernel/liveupdate/luo_file.c=474=int luo_file_freeze(struct luo_file_set file_set)\n--\nkernel/liveupdate/luo_file.c-476-\tstruct luo_file luo_file;\nkernel/liveupdate/luo_file.c:477:\tstruct kho_block_set_it it;\nkernel/liveupdate/luo_file.c-478-\tint err;\n--\nkernel/liveupdate/luo_file.c-482-\nkernel/liveupdate/luo_file.c:483:\tkho_block_set_it_init(\u0026it, \u0026file_set-\u003eblock_set);\nkernel/liveupdate/luo_file.c-484-\nkernel/liveupdate/luo_file.c-485-\tlist_for_each_entry(luo_file, \u0026file_set-\u003efiles_list, list) {\nkernel/liveupdate/luo_file.c:486:\t\tstruct luo_file_ser file_ser = kho_block_set_it_reserve_entry(\u0026it);\nkernel/liveupdate/luo_file.c-487-\n--\nkernel/liveupdate/luo_file.c=695=int luo_file_finish(struct luo_file_set file_set)\n--\nkernel/liveupdate/luo_file.c-723-\t\tfile_set-\u003ecount--;\nkernel/liveupdate/luo_file.c:724:\t\tkho_block_set_shrink(\u0026file_set-\u003eblock_set, file_set-\u003ecount);\nkernel/liveupdate/luo_file.c-725-\t\tmutex_destroy(\u0026luo_file-\u003emutex);\n--\nkernel/liveupdate/luo_file.c-728-\nkernel/liveupdate/luo_file.c:729:\tkho_block_set_destroy(\u0026file_set-\u003eblock_set);\nkernel/liveupdate/luo_file.c-730-\n--\nkernel/liveupdate/luo_file.c=799=int luo_file_deserialize(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-802-\tstruct luo_file_ser *file_ser;\nkernel/liveupdate/luo_file.c:803:\tstruct kho_block_set_it it;\nkernel/liveupdate/luo_file.c-804-\tint err;\n--\nkernel/liveupdate/luo_file.c-811-\tfile_set-\u003ecount = 0;\nkernel/liveupdate/luo_file.c:812:\terr = kho_block_set_restore(\u0026file_set-\u003eblock_set, file_set_ser-\u003efiles);\n\n" }
91/3	2026/10/26 02:31	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36181 output: 37 thoughts: 38 Thoughts: Okay, let's dive into this. Here's my understanding, presented as a personal thought process: Diving into `kho_block_alloc_ser` Alright, I'm curious about the behavior of this `kho_block_alloc_ser` function. I need to get a handle on what's going on inside. To start, I'll go directly to the source, specifically lines 70 through 110 of `kho_block.c`. That should give me the core logic of the function. I'll read it carefully, looking for allocation strategies, any locking mechanisms, and, importantly, how it interacts with the underlying memory management. I'm expecting some standard allocation routines, potentially with checks for available blocks, perhaps some bookkeeping to track usage, and likely some serialization to deal with concurrent access. This region should hopefully unveil the critical aspects of its operation. Time to read and understand.
92/3	2026/10/26 02:31	tool	read-file	0m Args: { "File": "kernel/liveupdate/kho_block.c", "FirstLine": 70, "LineCount": 40 } Results: { "Contents": " 70:\t\t\tkho_unpreserve_free(ser);\n 71:\t}\n 72:\t\n 73:\tstatic struct kho_block_header_ser kho_block_alloc_ser(struct kho_block_set bs)\n 74:\t{\n 75:\t\tWARN_ON_ONCE(bs-\u003eincoming);\n 76:\t\treturn kho_alloc_preserve(KHO_BLOCK_SIZE);\n 77:\t}\n 78:\t\n 79:\tstatic int kho_block_add(struct kho_block_set bs,\n 80:\t\t\t\t struct kho_block_header_ser ser)\n 81:\t{\n 82:\t\tstruct kho_block block, last;\n 83:\t\n 84:\t\tif (bs-\u003enblocks \u003e= KHO_MAX_BLOCKS)\n 85:\t\t\treturn -ENOSPC;\n 86:\t\n 87:\t\tblock = kzalloc_obj(block);\n 88:\t\tif (!block)\n 89:\t\t\treturn -ENOMEM;\n 90:\t\n 91:\t\tblock-\u003eser = ser;\n 92:\t\tlast = list_last_entry_or_null(\u0026bs-\u003eblocks, struct kho_block, list);\n 93:\t\tlist_add_tail(\u0026block-\u003elist, \u0026bs-\u003eblocks);\n 94:\t\tbs-\u003enblocks++;\n 95:\t\n 96:\t\tif (last)\n 97:\t\t\tlast-\u003eser-\u003enext = virt_to_phys(ser);\n 98:\t\telse\n 99:\t\t\tbs-\u003ehead_pa = virt_to_phys(ser);\n 100:\t\n 101:\t\treturn 0;\n 102:\t}\n 103:\t\n 104:\tstatic int kho_block_set_grow_one(struct kho_block_set bs)\n 105:\t{\n 106:\t\tstruct kho_block_header_ser *ser;\n 107:\t\tint err;\n 108:\t\n 109:\t\tser = kho_block_alloc_ser(bs);\n" }
93/3	2026/10/26 02:31	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36993 output: 19 thoughts: 11 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience and presented in the first person: Deep Dive into `kho_alloc_preserve` Alright, let's get down to brass tacks and take a closer look at `kho_alloc_preserve`. I need to assess its behavior and determine how it interacts with the broader memory management strategy, particularly in edge cases and scenarios with high contention. My primary concern is always memory integrity and performance. I need to understand its allocation guarantees, its interaction with the underlying allocator, and if it could potentially introduce fragmentation or contention bottlenecks. I'll need to scrutinize its internal implementation for any hidden assumptions or potential vulnerabilities. I'm thinking about the implications for multi-threaded access and how it handles different allocation sizes and alignment requirements. Essentially, I'm trying to figure out if this allocation function is as robust and efficient as it claims to be, or if there are any subtle pitfalls I need to be aware of. The aim is to fully understand how it fits into the bigger picture of memory management within the system.
94/3	2026/10/26 02:31	tool	grepper	0m Args: { "Expression": "kho_alloc_preserve" } Results: { "Output": "drivers/pci/liveupdate.c=269=static int pci_flb_preserve(struct liveupdate_flb_op_args args)\n--\ndrivers/pci/liveupdate.c-277-\ndrivers/pci/liveupdate.c:278:\tser = kho_alloc_preserve(sizeof(ser));\ndrivers/pci/liveupdate.c-279-\tif (IS_ERR(ser))\n--\ninclude/linux/kexec_handover.h=25=void kho_unpreserve_vmalloc(struct kho_vmalloc preservation);\ninclude/linux/kexec_handover.h:26:void kho_alloc_preserve(size_t size);\ninclude/linux/kexec_handover.h-27-void kho_unpreserve_free(void mem);\n--\ninclude/linux/kexec_handover.h=82=static inline void kho_unpreserve_vmalloc(struct kho_vmalloc preservation) { }\ninclude/linux/kexec_handover.h-83-\ninclude/linux/kexec_handover.h:84:static inline void kho_alloc_preserve(size_t size)\ninclude/linux/kexec_handover.h-85-{\n--\nkernel/liveupdate/kexec_handover.c=1542=EXPORT_SYMBOL_GPL(kho_restore_vmalloc);\n--\nkernel/liveupdate/kexec_handover.c-1544-/\nkernel/liveupdate/kexec_handover.c:1545: kho_alloc_preserve - Allocate, zero, and preserve memory.\nkernel/liveupdate/kexec_handover.c-1546- * @size: The number of bytes to allocate.\n--\nkernel/liveupdate/kexec_handover.c-1557- /\nkernel/liveupdate/kexec_handover.c:1558:void kho_alloc_preserve(size_t size)\nkernel/liveupdate/kexec_handover.c-1559-{\n--\nkernel/liveupdate/kexec_handover.c-1581-}\nkernel/liveupdate/kexec_handover.c:1582:EXPORT_SYMBOL_GPL(kho_alloc_preserve);\nkernel/liveupdate/kexec_handover.c-1583-\n--\nkernel/liveupdate/kexec_handover.c-1585- * kho_unpreserve_free - Unpreserve and free memory.\nkernel/liveupdate/kexec_handover.c:1586: * @mem: Pointer to the memory allocated by kho_alloc_preserve().\nkernel/liveupdate/kexec_handover.c-1587- \n--\nkernel/liveupdate/kexec_handover.c-1589- pages back to the system. This function should be called to clean up\nkernel/liveupdate/kexec_handover.c:1590: * memory allocated with kho_alloc_preserve().\nkernel/liveupdate/kexec_handover.c-1591- /\n--\nkernel/liveupdate/kexec_handover.c=1603=EXPORT_SYMBOL_GPL(kho_unpreserve_free);\n--\nkernel/liveupdate/kexec_handover.c-1611- to take ownership of and free a memory region that was preserved by the\nkernel/liveupdate/kexec_handover.c:1612: * old kernel using kho_alloc_preserve().\nkernel/liveupdate/kexec_handover.c-1613- \n--\nkernel/liveupdate/kexec_handover.c=1792=static __init int kho_out_kexec_metadata(void)\n--\nkernel/liveupdate/kexec_handover.c-1796-\nkernel/liveupdate/kexec_handover.c:1797:\tmetadata = kho_alloc_preserve(sizeof(metadata));\nkernel/liveupdate/kexec_handover.c-1798-\tif (IS_ERR(metadata))\n--\nkernel/liveupdate/kexec_handover.c=1831=static __init int kho_init(void)\n--\nkernel/liveupdate/kexec_handover.c-1843-\nkernel/liveupdate/kexec_handover.c:1844:\tkho_out.fdt = kho_alloc_preserve(PAGE_SIZE);\nkernel/liveupdate/kexec_handover.c-1845-\tif (IS_ERR(kho_out.fdt)) {\n--\nkernel/liveupdate/kho_block.c=73=static struct kho_block_header_ser kho_block_alloc_ser(struct kho_block_set bs)\n--\nkernel/liveupdate/kho_block.c-75-\tWARN_ON_ONCE(bs-\u003eincoming);\nkernel/liveupdate/kho_block.c:76:\treturn kho_alloc_preserve(KHO_BLOCK_SIZE);\nkernel/liveupdate/kho_block.c-77-}\n--\nkernel/liveupdate/luo_core.c=154=static int __init luo_state_setup(void)\n--\nkernel/liveupdate/luo_core.c-158-\nkernel/liveupdate/luo_core.c:159:\tluo_ser = kho_alloc_preserve(sizeof(luo_ser));\nkernel/liveupdate/luo_core.c-160-\tif (IS_ERR(luo_ser)) {\n--\nkernel/liveupdate/luo_flb.c=560=int __init luo_flb_setup_outgoing(u64 flbs_pa)\n--\nkernel/liveupdate/luo_flb.c-563-\nkernel/liveupdate/luo_flb.c:564:\theader_ser = kho_alloc_preserve(LUO_FLB_PGCNT \u003c\u003c PAGE_SHIFT);\nkernel/liveupdate/luo_flb.c-565-\tif (IS_ERR(header_ser))\n--\nmm/memfd_luo.c=258=static int memfd_luo_preserve(struct liveupdate_file_op_args args)\n--\nmm/memfd_luo.c-269-\t/ Allocate the main serialization structure in preserved memory /\nmm/memfd_luo.c:270:\tser = kho_alloc_preserve(sizeof(ser));\nmm/memfd_luo.c-271-\tif (IS_ERR(ser)) {\n" }
95/3	2026/10/26 02:31	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38853 output: 31 thoughts: 306 Thoughts: Analyzing `memfd_luo.c` and Memory Preservation Okay, so `kho_alloc_preserve` uses `__GFP_ZERO` or `kzalloc` to allocate, zero, and preserve memory – standard fare. I need to understand what `memfd_luo` does with freezing, specifically, how it interacts with memory preservation during that process. Looking at the diff, it clarifies how freezing interacts with file state. It preserves the file position at the time of freezing, which makes sense for resuming read/write operations later. The diff also confirms that memfds are always opened with `O_RDWR` and `O_LARGEFILE`, as expected. Hmm... was `.freeze()` actually implemented within `memfd_luo.c`? That would be a key piece of information. I should quickly search the `memfd_luo` code for the strings ".freeze" or "freeze" to confirm that it's there. That will tell me if this is a primary implementation or if this file relies on another module for the freeze operation.
96/3	2026/10/26 02:31	tool	grepper	0m Args: { "Expression": "freeze", "PathPrefixes": [ "mm/memfd_luo.c" ] } Results: { "Output": "mm/memfd_luo.c=88=static int memfd_luo_preserve_folios(struct file file,\n--\nmm/memfd_luo.c-163-\t\t Saving the dirty flag at prepare() time doesn't work since it\nmm/memfd_luo.c:164:\t\t * can change later. Saving it at freeze() also won't work\nmm/memfd_luo.c-165-\t\t * because the dirty bit is normally synced at unmap and there\nmm/memfd_luo.c:166:\t\t * might still be a mapping of the file at freeze().\nmm/memfd_luo.c-167-\t\t \n--\nmm/memfd_luo.c=258=static int memfd_luo_preserve(struct liveupdate_file_op_args args)\n--\nmm/memfd_luo.c-266-\tinode_lock(inode);\nmm/memfd_luo.c:267:\tshmem_freeze(inode, true);\nmm/memfd_luo.c-268-\n--\nmm/memfd_luo.c-318-err_unlock:\nmm/memfd_luo.c:319:\tshmem_freeze(inode, false);\nmm/memfd_luo.c-320-\tinode_unlock(inode);\n--\nmm/memfd_luo.c-323-\nmm/memfd_luo.c:324:static int memfd_luo_freeze(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-325-{\n--\nmm/memfd_luo.c=342=static void memfd_luo_unpreserve(struct liveupdate_file_op_args args)\n--\nmm/memfd_luo.c-350-\tinode_lock(inode);\nmm/memfd_luo.c:351:\tshmem_freeze(inode, false);\nmm/memfd_luo.c-352-\n--\nmm/memfd_luo.c=593=static const struct liveupdate_file_ops memfd_luo_file_ops = {\nmm/memfd_luo.c:594:\t.freeze = memfd_luo_freeze,\nmm/memfd_luo.c-595-\t.finish = memfd_luo_finish,\n" }
97/3	2026/10/26 02:31	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 40032 output: 37 thoughts: 25 Thoughts: Okay, here's my attempt at summarizing the thought process, as requested, targeting an expert audience and written in the first person: Diving into memfd_luo_freeze Right, let's get down to brass tacks. I need to understand this `memfd_luo_freeze` function. That means I'm pulling up `mm/memfd_luo.c`. My immediate goal is to understand how this freeze mechanism works within the context of the LUO (Linux User-space Overlay) memfd functionality. I expect I'll be looking for critical sections, locking mechanisms, and the overall strategy for quiescing or synchronizing memory regions. I'm especially interested in how it interacts with page faults, copy-on-write operations, and any potential for deadlock. I'll be mentally parsing the code for any subtle data races or concurrency issues. Time to dig in and see how the kernel handles this.
98/3	2026/10/26 02:32	tool	read-file	0m Args: { "File": "mm/memfd_luo.c", "FirstLine": 320, "LineCount": 25 } Results: { "Contents": " 320:\t\tinode_unlock(inode);\n 321:\t\treturn err;\n 322:\t}\n 323:\t\n 324:\tstatic int memfd_luo_freeze(struct liveupdate_file_op_args args)\n 325:\t{\n 326:\t\tstruct memfd_luo_ser ser;\n 327:\t\n 328:\t\tif (WARN_ON_ONCE(!args-\u003eserialized_data))\n 329:\t\t\treturn -EINVAL;\n 330:\t\n 331:\t\tser = phys_to_virt(args-\u003eserialized_data);\n 332:\t\n 333:\t\t/\n 334:\t\t The pos might have changed since prepare. Everything else stays the\n 335:\t\t * same.\n 336:\t\t /\n 337:\t\tser-\u003epos = args-\u003efile-\u003ef_pos;\n 338:\t\n 339:\t\treturn 0;\n 340:\t}\n 341:\t\n 342:\tstatic void memfd_luo_unpreserve(struct liveupdate_file_op_args args)\n 343:\t{\n 344:\t\tstruct inode *inode = file_inode(args-\u003efile);\n" }
99/3	2026/10/26 02:32	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 40631 output: 349 thoughts: 2196 Thoughts: KMSAN Applicability Analysis for Live Update Session Freeze Patch Okay, let's break this down. First, the patch introduces a new ioctl, `LIVEUPDATE_SESSION_FREEZE`, enabling userspace to freeze a live update session. I've walked through the changes, focusing on potential KMSAN (Kernel Memory Sanitizer) issues: situations where uninitialized kernel memory might leak to userspace or be used in conditional logic. The core of the new functionality lies in `luo_session_freeze`. Looking at the code, it involves these key steps: 1. User-Space Interaction: The `luo_session_freeze` function receives a `struct liveupdate_session_freeze` from userspace via the `ucmd->cmd` pointer. Crucially, the data is copied from user space to kernel via `copy_struct_from_user`. The function then copies the structure back to user space via `luo_ucmd_respond`, using `copy_to_user`. 2. Initialization: The `struct liveupdate_session_freeze` struct consists of two `__u32` fields: `size` and `reserved`. The key here is the initialization of the data; the memory is initialized by the copy from user space. 3. No Uninitialized Data Leak: No data is written into `argp` other than user-provided data. This is copied back to user space in `luo_ucmd_respond` is therefore initialized by the `copy_struct_from_user` call. Since the relevant structure fields are populated with user-provided data, and no other fields are being touched, there's no risk of leaking uninitialized kernel memory to userspace. 4. No Conditional Logic on Uninitialized Data: The `reserved` field is checked for non-zero values, coming from userspace. `session->user_frozen` is initialized to `false` at `luo_session_alloc` and `file_set->count` is initialized in `luo_file_set_init`. 5. No Complex Data Structures with Potential Uninitialized Fields: The patch doesn't introduce any complex data structures that could lead to uninitialized memory reads. 6. No Buffer Overflows with Uninitialized Data: The patch does not appear to use any bounds checks that could result in uninitialized bytes being read. I've checked other relevant functions, like `luo_session_finish`, which follows a similar pattern and does not provide an opportunity for uninitialized memory issues. I've also examined the `luo_session_serialize_one` function, where liveupdate data is copied into buffers to be sent to userspace. This function uses zeroed allocated buffers. The relevant data is copied into the buffer after the allocation, therefore there is no risk of uninitialized memory. Furthermore, I can see that `ser->name` is already initialized, because it's populated with `strscpy`, which zero-terminates or zero-fills based on size. Given the nature of the changes, the existing kernel sanitizers (KASAN and LOCKDEP) appear to be sufficient to catch any potential issues like concurrency bugs, use-after-free conditions, state machine bugs, or memory leaks. Therefore, this patch does not require KMSAN, the `NeedsKMSAN` flag is `false`. ``` set-results NeedsKMSAN false ```
100/3	2026/10/26 02:32	tool	set-results	0m Args: { "KMSANReasoning": "The patch introduces the `LIVEUPDATE_SESSION_FREEZE` ioctl, allowing userspace to explicitly freeze a live-update session before kexec reboot.\n\nFrom a memory initialization and info-leak standpoint:\n1. User-kernel interface: The new ioctl parameter structure `struct liveupdate_session_freeze` consists of two `__u32` fields (`size` and `reserved`) with no structure padding (8 bytes total). In `luo_session_ioctl()`, input is copied and validated using `copy_struct_from_user()`, which zeroes any uncopied bytes within the kernel size. The ioctl response via `luo_ucmd_respond()` copies back the struct without exposing uninitialized stack or heap bytes.\n2. Internal state and structures: `struct luo_session` is allocated via `kzalloc_obj()`, ensuring the newly added `bool user_frozen` field is initialized to false. KHO serialization buffers are allocated using `kho_alloc_preserve()`, which zeroes allocated memory.\n3. Bug surface: The primary risks associated with this patch involve session state transitions, lifecycle management (freeze/unfreeze on error/release), concurrency (guarded by mutex and rwsem), or error handling logic. Such bugs (e.g. use-after-free, double free, locking anomalies) are fully covered by KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nBecause no uninitialized memory reads or information leak hazards are introduced, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch introduces the `LIVEUPDATE_SESSION_FREEZE` ioctl, allowing userspace to explicitly freeze a live-update session before kexec reboot.\n\nFrom a memory initialization and info-leak standpoint:\n1. User-kernel interface: The new ioctl parameter structure `struct liveupdate_session_freeze` consists of two `__u32` fields (`size` and `reserved`) with no structure padding (8 bytes total). In `luo_session_ioctl()`, input is copied and validated using `copy_struct_from_user()`, which zeroes any uncopied bytes within the kernel size. The ioctl response via `luo_ucmd_respond()` copies back the struct without exposing uninitialized stack or heap bytes.\n2. Internal state and structures: `struct luo_session` is allocated via `kzalloc_obj()`, ensuring the newly added `bool user_frozen` field is initialized to false. KHO serialization buffers are allocated using `kho_alloc_preserve()`, which zeroes allocated memory.\n3. Bug surface: The primary risks associated with this patch involve session state transitions, lifecycle management (freeze/unfreeze on error/release), concurrency (guarded by mutex and rwsem), or error handling logic. Such bugs (e.g. use-after-free, double free, locking anomalies) are fully covered by KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nBecause no uninitialized memory reads or information leak hazards are introduced, a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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