AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/26 19:12	flow	patch-triage	3m Args: null Results: { "EnableConfigs": [ "SYSCTL", "PROC_FS", "SYSVIPC", "POSIX_MQUEUE", "IPC_NS" ], "FocusSymbols": [ "__register_sysctl_table_ctx", "sysctl_apply_ctx", "proc_sys_call_handler", "proc_sys_permission", "sysctl_check_table", "setup_ipc_sysctls", "setup_mq_sysctls" ], "KMSANReasoning": "The patch refactors per-namespace sysctl tables in IPC and POSIX message queues (mq) to eliminate dynamic kmemdup allocations. Instead, it introduces `struct sysctl_context` and a flag `CTL_TABLE_F_CTX_DATA` to resolve per-namespace struct member offsets dynamically via `sysctl_apply_ctx()` into a local stack buffer (`ctx_entry`).\n\nKMSAN vs KASAN applicability analysis:\n1. Uninitialized memory reads / branching:\n - The stack variables `struct ctl_table ctx_entry` in `proc_sys_call_handler()` and `proc_sys_permission()` are passed as out-parameters to `sysctl_apply_ctx()`. When `CTL_TABLE_F_CTX_DATA` is set, `buf = entry;` fully initializes the struct from the static const sysctl table before updating `buf-\u003edata` and returning `buf`. When the flag is not set, `sysctl_apply_ctx()` returns `entry` directly, leaving `buf` untouched and completely unreferenced.\n - The `struct sysctl_context` created by `SYSCTL_CTX` initializes all struct fields (`inst` and `tmpl`) via a compound literal.\n - `struct ctl_table_header` is allocated using `kzalloc()`, and `struct ipc_namespace` is allocated using `kzalloc_obj()`.\n2. Kernel-to-userspace info-leaks:\n - `struct ctl_table` is an internal kernel structure and is never copied to user space. Data written to userspace by sysctl read handlers is formatted into `kbuf` allocated with `kvzalloc()`.\n3. Memory safety risks:\n - Any potential offset calculation errors (`(char *)head-\u003ectx.inst + off`) would lead to out-of-bounds pointer dereferences, which are detected by KASAN, not KMSAN.\n\nTherefore, the patch does not expose any uninitialized memory risks or info-leaks. A dedicated KMSAN fuzzing session is not warranted; standard KASAN fuzzing is sufficient.", "NeedsKMSAN": false, "Reasoning": "The patch introduces a new context-based data pointer resolution mechanism for sysctl entries (CTL_TABLE_F_CTX_DATA) to avoid duplicating ctl_tables when instantiating new IPC namespaces. This alters pointer calculation in core sysctl access paths (proc_sys_call_handler, proc_sys_permission) and adds new table validation checks in sysctl_check_table and __register_sysctl_table_ctx. This code is fully reachable via standard unshare(CLONE_NEWIPC) and /proc/sys read/write operations, making it valuable to fuzz for potential out-of-bounds pointer calculation issues or registration inconsistencies.", "WorthFuzzing": true }
1/1	2026/09/26 19:12	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 72956c04a50c26de34979e555c595f8609103b90\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Sat Sep 26 19:12:52 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c\nindex 04a382178c657..1ed9f4e1a17e2 100644\n--- a/fs/proc/proc_sysctl.c\n+++ b/fs/proc/proc_sysctl.c\n@@ -550,12 +550,31 @@ static struct dentry proc_sys_lookup(struct inode dir, struct dentry dentry,\n \treturn err;\n }\n \n+/ Returns @entry itself when it is not flagged, else a resolved copy in @buf. /\n+static const struct ctl_table sysctl_apply_ctx(struct ctl_table_header head,\n+\t\t\t\t\t\tconst struct ctl_table entry,\n+\t\t\t\t\t\tstruct ctl_table buf)\n+{\n+\tptrdiff_t off;\n+\n+\tif (!(entry-\u003eflags \u0026 CTL_TABLE_F_CTX_DATA))\n+\t\treturn entry;\n+\n+\toff = (const char )entry-\u003edata - (const char )head-\u003ectx.tmpl;\n+\n+\tbuf = entry;\n+\tbuf-\u003edata = (char )head-\u003ectx.inst + off;\n+\n+\treturn buf;\n+}\n+\n static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter,\n \t\tint write)\n {\n \tstruct inode inode = file_inode(iocb-\u003eki_filp);\n \tstruct ctl_table_header head = grab_header(inode);\n \tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\n+\tstruct ctl_table ctx_entry;\n \tsize_t count = iov_iter_count(iter);\n \tchar kbuf;\n \tssize_t error;\n@@ -567,6 +586,8 @@ static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter,\n \t * At this point we know that the sysctl was not unregistered\n \t * and won't be until we finish.\n \t /\n+\ttable = sysctl_apply_ctx(head, table, \u0026ctx_entry);\n+\n \terror = -EPERM;\n \tif (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))\n \t\tgoto out;\n@@ -797,6 +818,7 @@ static int proc_sys_permission(struct mnt_idmap idmap,\n \t /\n \tstruct ctl_table_header head;\n \tconst struct ctl_table table;\n+\tstruct ctl_table ctx_entry;\n \tint error;\n \n \t/ Executable files are not allowed under /proc/sys/ /\n@@ -810,8 +832,11 @@ static int proc_sys_permission(struct mnt_idmap idmap,\n \ttable = PROC_I(inode)-\u003esysctl_entry;\n \tif (!table) /* global root - r-xr-xr-x /\n \t\terror = mask \u0026 MAY_WRITE ? -EACCES : 0;\n-\telse / Use the permissions on the sysctl table entry /\n+\telse {\n+\t\t/ -\u003epermissions may inspect the entry, so resolve it first. /\n+\t\ttable = sysctl_apply_ctx(head, table, \u0026ctx_entry);\n \t\terror = sysctl_perm(head, table, mask \u0026 ~MAY_NOT_BLOCK);\n+\t}\n \n \tsysctl_head_finish(head);\n \treturn error;\n@@ -1143,10 +1168,18 @@ static int sysctl_check_table_array(const char path, const struct ctl_table ta\n static int sysctl_check_table(const char path, struct ctl_table_header header)\n {\n \tconst struct ctl_table entry;\n+\tu8 flagged = 0;\n \tint err = 0;\n \tlist_for_each_table_entry(entry, header) {\n \t\tif (!entry-\u003eprocname)\n \t\t\terr \|= sysctl_err(path, entry, \"procname is null\");\n+\t\tif (entry-\u003eflags \u0026 CTL_TABLE_F_CTX_DATA) {\n+\t\t\tif (!entry-\u003edata)\n+\t\t\t\terr \|= sysctl_err(path, entry, \"No data to resolve\");\n+\t\t\tif (!header-\u003ectx.inst \|\| !header-\u003ectx.tmpl)\n+\t\t\t\terr \|= sysctl_err(path, entry, \"No context to resolve against\");\n+\t\t}\n+\t\tflagged \|= entry-\u003eflags \u0026 CTL_TABLE_F_CTX;\n \t\tif ((entry-\u003eproc_handler == proc_dostring) \|\|\n \t\t (entry-\u003eproc_handler == proc_dobool) \|\|\n \t\t (entry-\u003eproc_handler == proc_dointvec) \|\|\n@@ -1173,6 +1206,12 @@ static int sysctl_check_table(const char path, struct ctl_table_header header)\n \t\t\terr \|= sysctl_err(path, entry, \"bogus .mode 0%o\",\n \t\t\t\tentry-\u003emode);\n \t}\n+\t/* A context nobody resolves against is a forgotten flag. /\n+\tif (!flagged \u0026\u0026 (header-\u003ectx.inst \|\| header-\u003ectx.tmpl)) {\n+\t\tpr_err(\"sysctl table check failed: %s context given but no entry is flagged\\n\",\n+\t\t path);\n+\t\terr = -EINVAL;\n+\t}\n \treturn err;\n }\n \n@@ -1324,7 +1363,7 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path)\n }\n \n /*\n- __register_sysctl_table - register a leaf sysctl table\n+ * __register_sysctl_table_ctx - register a leaf sysctl table\n * @set: Sysctl tree to register on\n * @path: The path to the directory the sysctl table is in.\n \n@@ -1333,6 +1372,9 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path)\n * be a global or dynamically allocated by the caller and free'd later\n * after sysctl unregistration.\n * @table_size : The number of elements in table\n+ * @ctx: instances that entries flagged CTL_TABLE_F_CTX_* resolve against, see\n+ * struct sysctl_context. Copied, so it may be on stack. %NULL when no\n+ * entry is flagged.\n \n Register a sysctl table hierarchy. @table should be a filled in ctl_table\n * array.\n@@ -1343,6 +1385,7 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path)\n data - a pointer to data for use by proc_handler\n * maxlen - the maximum size in bytes of the data\n * mode - the file permissions for the /proc/sys file\n+ * flags - CTL_TABLE_F_* bits naming members to resolve against @ctx\n * type - Defines the target type (described in struct definition)\n * proc_handler - the text handler routine (described below)\n \n@@ -1366,9 +1409,10 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path)\n * This routine returns %NULL on a failure to register, and a pointer\n * to the table header on success.\n /\n-struct ctl_table_header __register_sysctl_table(\n+struct ctl_table_header __register_sysctl_table_ctx(\n \tstruct ctl_table_set set,\n-\tconst char path, const struct ctl_table table, size_t table_size)\n+\tconst char path, const struct ctl_table table, size_t table_size,\n+\tconst struct sysctl_context ctx)\n {\n \tstruct ctl_table_root root = set-\u003edir.header.root;\n \tstruct ctl_table_header header;\n@@ -1382,6 +1426,8 @@ struct ctl_table_header __register_sysctl_table(\n \n \tnode = (struct ctl_node )(header + 1);\n \tinit_header(header, root, set, node, table, table_size);\n+\tif (ctx)\n+\t\theader-\u003ectx = ctx;\n \tif (sysctl_check_table(path, header))\n \t\tgoto fail;\n \n@@ -1427,7 +1473,7 @@ struct ctl_table_header __register_sysctl_table(\n Register a sysctl table. @table should be a filled in ctl_table\n * array. A completely 0 filled entry terminates the table.\n \n- See __register_sysctl_table for more details.\n+ * See __register_sysctl_table_ctx for more details.\n /\n struct ctl_table_header register_sysctl_sz(const char path, const struct ctl_table table,\n \t\t\t\t\t size_t table_size)\ndiff --git a/include/linux/sysctl.h b/include/linux/sysctl.h\nindex e5d7226ab6f5a..b2c57c530bdc9 100644\n--- a/include/linux/sysctl.h\n+++ b/include/linux/sysctl.h\n@@ -22,6 +22,8 @@\n #ifndef _LINUX_SYSCTL_H\n #define _LINUX_SYSCTL_H\n \n+#include \u003clinux/bits.h\u003e\n+#include \u003clinux/build_bug.h\u003e\n #include \u003clinux/list.h\u003e\n #include \u003clinux/rcupdate.h\u003e\n #include \u003clinux/wait.h\u003e\n@@ -224,12 +226,50 @@ struct ctl_table {\n \tvoid data;\n \tint maxlen;\n \tumode_t mode;\n+\tu8 flags;\t\t\t/ CTL_TABLE_F_* /\n \tproc_handler proc_handler;\t/* Callback for text formatting /\n \tstruct ctl_table_poll poll;\n \tvoid extra1;\n \tvoid extra2;\n } __randomize_layout;\n \n+/\n+ ctl_table::flags. Resolve the corresponding member against the\n+ * registration context instead of using it as it stands.\n+ /\n+#define CTL_TABLE_F_CTX_DATA\tBIT(0)\n+#define CTL_TABLE_F_CTX\t\tCTL_TABLE_F_CTX_DATA\n+\n+/\n+ struct sysctl_context - ctl_table specific context\n+ * @inst: entry location\n+ * @tmpl: struct template (used to calculate offset into @inst)\n+ \n+ @inst/@tmpl pair is used to overlay the ctl_table entry before calling\n+ * proc_handler. This is relevant when struct members (like -\u003edata) are\n+ * somewhere different than the const static ctl_table array (think\n+ * namespaces). Build it with SYSCTL_CTX() so the compiler checks that\n+ * both point at the same type.\n+ /\n+struct sysctl_context {\n+\tvoid inst;\n+\tconst void tmpl;\n+};\n+\n+/\n+ SYSCTL_CTX - build a struct sysctl_context\n+ * @_inst: the instance this registration describes\n+ * @_tmpl: the instance the table's data members name\n+ \n+ Fails to build unless @_inst and @_tmpl point at the same type.\n+ /\n+#define SYSCTL_CTX(_inst, _tmpl)\t\t\t\t\t\\\n+\t((struct sysctl_context){\t\t\t\t\t\\\n+\t\t.inst = (_inst) +\t\t\t\t\t\\\n+\t\t\tBUILD_BUG_ON_ZERO(!__same_type((_inst), (_tmpl))), \\\n+\t\t.tmpl = (_tmpl),\t\t\t\t\t\\\n+\t})\n+\n struct ctl_node {\n \tstruct rb_node node;\n \tstruct ctl_table_header header;\n@@ -244,6 +284,7 @@ struct ctl_node {\n * something is removed from inodes\n * @nreg: When nreg drops to 0 the ctl_table_header will be unregistered.\n * @rcu: Delays the freeing of the inode. Introduced with \"unfuck proc_sysctl -\u003ed_compare()\"\n+ * @ctx: instances given to __register_sysctl_table_ctx(), see struct sysctl_context\n \n @type: Enumeration to differentiate between ctl target types:\n * type.SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations\n@@ -268,6 +309,7 @@ struct ctl_table_header {\n \tstruct ctl_dir parent;\n \tstruct ctl_node node;\n \tstruct hlist_head inodes; /* head for proc_inode-\u003esysctl_inodes /\n+\tstruct sysctl_context ctx;\n \tenum {\n \t\tSYSCTL_TABLE_TYPE_DEFAULT,\n \t\tSYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY,\n@@ -305,9 +347,18 @@ extern void setup_sysctl_set(struct ctl_table_set p,\n \tint (is_seen)(struct ctl_table_set ));\n extern void retire_sysctl_set(struct ctl_table_set set);\n \n-struct ctl_table_header __register_sysctl_table(\n+struct ctl_table_header __register_sysctl_table_ctx(\n+\tstruct ctl_table_set set,\n+\tconst char path, const struct ctl_table table, size_t table_size,\n+\tconst struct sysctl_context ctx);\n+\n+static inline struct ctl_table_header __register_sysctl_table(\n \tstruct ctl_table_set set,\n-\tconst char path, const struct ctl_table table, size_t table_size);\n+\tconst char path, const struct ctl_table table, size_t table_size)\n+{\n+\treturn __register_sysctl_table_ctx(set, path, table, table_size, NULL);\n+}\n+\n struct ctl_table_header register_sysctl_sz(const char path, const struct ctl_table table,\n \t\t\t\t\t size_t table_size);\n void unregister_sysctl_table(struct ctl_table_header * table);\ndiff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c\nindex d038d944257f6..5d73487bb81c0 100644\n--- a/ipc/ipc_sysctl.c\n+++ b/ipc/ipc_sysctl.c\n@@ -13,7 +13,6 @@\n #include \u003clinux/capability.h\u003e\n #include \u003clinux/ipc_namespace.h\u003e\n #include \u003clinux/msg.h\u003e\n-#include \u003clinux/slab.h\u003e\n #include \u003clinux/cred.h\u003e\n #include \"util.h\"\n \n@@ -79,6 +78,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.shm_ctlmax,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.shm_ctlmax),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_doulongvec_minmax,\n \t},\n \t{\n@@ -86,6 +86,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.shm_ctlall,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.shm_ctlall),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_doulongvec_minmax,\n \t},\n \t{\n@@ -93,6 +94,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.shm_ctlmni,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.shm_ctlmni),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= \u0026ipc_mni,\n@@ -102,6 +104,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.shm_rmid_forced,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.shm_rmid_forced),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_ipc_dointvec_minmax_orphans,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= SYSCTL_ONE,\n@@ -111,6 +114,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.msg_ctlmax,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.msg_ctlmax),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= SYSCTL_INT_MAX,\n@@ -120,6 +124,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.msg_ctlmni,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.msg_ctlmni),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= \u0026ipc_mni,\n@@ -138,6 +143,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.msg_ctlmnb,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.msg_ctlmnb),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= SYSCTL_INT_MAX,\n@@ -147,6 +153,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.sem_ctls,\n \t\t.maxlen\t\t= 4sizeof(int),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_ipc_sem_dointvec,\n \t},\n #ifdef CONFIG_CHECKPOINT_RESTORE\n@@ -155,6 +162,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.ids[IPC_SEM_IDS].next_id,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),\n \t\t.mode\t\t= 0444,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= SYSCTL_INT_MAX,\n@@ -164,6 +172,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.ids[IPC_MSG_IDS].next_id,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),\n \t\t.mode\t\t= 0444,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= SYSCTL_INT_MAX,\n@@ -173,6 +182,7 @@ static const struct ctl_table ipc_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.ids[IPC_SHM_IDS].next_id,\n \t\t.maxlen\t\t= sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),\n \t\t.mode\t\t= 0444,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= SYSCTL_INT_MAX,\n@@ -244,57 +254,15 @@ static struct ctl_table_root set_root = {\n \n bool setup_ipc_sysctls(struct ipc_namespace ns)\n {\n-\tstruct ctl_table tbl;\n+\tstruct sysctl_context ctx = SYSCTL_CTX(ns, \u0026init_ipc_ns);\n \n \tsetup_sysctl_set(\u0026ns-\u003eipc_set, \u0026set_root, set_is_seen);\n \n-\ttbl = kmemdup(ipc_sysctls, sizeof(ipc_sysctls), GFP_KERNEL);\n-\tif (tbl) {\n-\t\tint i;\n-\n-\t\tfor (i = 0; i \u003c ARRAY_SIZE(ipc_sysctls); i++) {\n-\t\t\tif (tbl[i].data == \u0026init_ipc_ns.shm_ctlmax)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_ctlmax;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.shm_ctlall)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_ctlall;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.shm_ctlmni)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_ctlmni;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.shm_rmid_forced)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003eshm_rmid_forced;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.msg_ctlmax)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emsg_ctlmax;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.msg_ctlmni)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emsg_ctlmni;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.msg_ctlmnb)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emsg_ctlmnb;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.sem_ctls)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003esem_ctls;\n-#ifdef CONFIG_CHECKPOINT_RESTORE\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.ids[IPC_SEM_IDS].next_id)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003eids[IPC_SEM_IDS].next_id;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.ids[IPC_MSG_IDS].next_id)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003eids[IPC_MSG_IDS].next_id;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.ids[IPC_SHM_IDS].next_id)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003eids[IPC_SHM_IDS].next_id;\n-#endif\n-\t\t\telse\n-\t\t\t\ttbl[i].data = NULL;\n-\t\t}\n-\n-\t\tns-\u003eipc_sysctls = __register_sysctl_table(\u0026ns-\u003eipc_set, \"kernel\", tbl,\n-\t\t\t\t\t\t\t ARRAY_SIZE(ipc_sysctls));\n-\t}\n+\tns-\u003eipc_sysctls = __register_sysctl_table_ctx(\u0026ns-\u003eipc_set, \"kernel\",\n+\t\t\t\t\t\t ipc_sysctls,\n+\t\t\t\t\t\t ARRAY_SIZE(ipc_sysctls),\n+\t\t\t\t\t\t \u0026ctx);\n \tif (!ns-\u003eipc_sysctls) {\n-\t\tkfree(tbl);\n \t\tretire_sysctl_set(\u0026ns-\u003eipc_set);\n \t\treturn false;\n \t}\n@@ -304,12 +272,8 @@ bool setup_ipc_sysctls(struct ipc_namespace ns)\n \n void retire_ipc_sysctls(struct ipc_namespace ns)\n {\n-\tconst struct ctl_table tbl;\n-\n-\ttbl = ns-\u003eipc_sysctls-\u003ectl_table_arg;\n \tunregister_sysctl_table(ns-\u003eipc_sysctls);\n \tretire_sysctl_set(\u0026ns-\u003eipc_set);\n-\tkfree(tbl);\n }\n \n static int __init ipc_sysctl_init(void)\ndiff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c\nindex 0dd12e1c9f53e..9919e2d3a11a4 100644\n--- a/ipc/mq_sysctl.c\n+++ b/ipc/mq_sysctl.c\n@@ -11,7 +11,6 @@\n \n #include \u003clinux/stat.h\u003e\n #include \u003clinux/capability.h\u003e\n-#include \u003clinux/slab.h\u003e\n #include \u003clinux/cred.h\u003e\n \n static int msg_max_limit_min = MIN_MSGMAX;\n@@ -26,6 +25,7 @@ static const struct ctl_table mq_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.mq_queues_max,\n \t\t.maxlen\t\t= sizeof(int),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec,\n \t},\n \t{\n@@ -33,6 +33,7 @@ static const struct ctl_table mq_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.mq_msg_max,\n \t\t.maxlen\t\t= sizeof(int),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= \u0026msg_max_limit_min,\n \t\t.extra2\t\t= \u0026msg_max_limit_max,\n@@ -42,6 +43,7 @@ static const struct ctl_table mq_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.mq_msgsize_max,\n \t\t.maxlen\t\t= sizeof(int),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= \u0026msg_maxsize_limit_min,\n \t\t.extra2\t\t= \u0026msg_maxsize_limit_max,\n@@ -51,6 +53,7 @@ static const struct ctl_table mq_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.mq_msg_default,\n \t\t.maxlen\t\t= sizeof(int),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= \u0026msg_max_limit_min,\n \t\t.extra2\t\t= \u0026msg_max_limit_max,\n@@ -60,6 +63,7 @@ static const struct ctl_table mq_sysctls[] = {\n \t\t.data\t\t= \u0026init_ipc_ns.mq_msgsize_default,\n \t\t.maxlen\t\t= sizeof(int),\n \t\t.mode\t\t= 0644,\n+\t\t.flags\t\t= CTL_TABLE_F_CTX_DATA,\n \t\t.proc_handler\t= proc_dointvec_minmax,\n \t\t.extra1\t\t= \u0026msg_maxsize_limit_min,\n \t\t.extra2\t\t= \u0026msg_maxsize_limit_max,\n@@ -116,39 +120,15 @@ static struct ctl_table_root set_root = {\n \n bool setup_mq_sysctls(struct ipc_namespace ns)\n {\n-\tstruct ctl_table tbl;\n+\tstruct sysctl_context ctx = SYSCTL_CTX(ns, \u0026init_ipc_ns);\n \n \tsetup_sysctl_set(\u0026ns-\u003emq_set, \u0026set_root, set_is_seen);\n \n-\ttbl = kmemdup(mq_sysctls, sizeof(mq_sysctls), GFP_KERNEL);\n-\tif (tbl) {\n-\t\tint i;\n-\n-\t\tfor (i = 0; i \u003c ARRAY_SIZE(mq_sysctls); i++) {\n-\t\t\tif (tbl[i].data == \u0026init_ipc_ns.mq_queues_max)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emq_queues_max;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.mq_msg_max)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emq_msg_max;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.mq_msgsize_max)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emq_msgsize_max;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.mq_msg_default)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emq_msg_default;\n-\n-\t\t\telse if (tbl[i].data == \u0026init_ipc_ns.mq_msgsize_default)\n-\t\t\t\ttbl[i].data = \u0026ns-\u003emq_msgsize_default;\n-\t\t\telse\n-\t\t\t\ttbl[i].data = NULL;\n-\t\t}\n-\n-\t\tns-\u003emq_sysctls = __register_sysctl_table(\u0026ns-\u003emq_set,\n-\t\t\t\t\t\t\t \"fs/mqueue\", tbl,\n-\t\t\t\t\t\t\t ARRAY_SIZE(mq_sysctls));\n-\t}\n+\tns-\u003emq_sysctls = __register_sysctl_table_ctx(\u0026ns-\u003emq_set, \"fs/mqueue\",\n+\t\t\t\t\t\t mq_sysctls,\n+\t\t\t\t\t\t ARRAY_SIZE(mq_sysctls),\n+\t\t\t\t\t\t \u0026ctx);\n \tif (!ns-\u003emq_sysctls) {\n-\t\tkfree(tbl);\n \t\tretire_sysctl_set(\u0026ns-\u003emq_set);\n \t\treturn false;\n \t}\n@@ -158,10 +138,6 @@ bool setup_mq_sysctls(struct ipc_namespace ns)\n \n void retire_mq_sysctls(struct ipc_namespace ns)\n {\n-\tconst struct ctl_table *tbl;\n-\n-\ttbl = ns-\u003emq_sysctls-\u003ectl_table_arg;\n \tunregister_sysctl_table(ns-\u003emq_sysctls);\n \tretire_sysctl_set(\u0026ns-\u003emq_set);\n-\tkfree(tbl);\n }\n" }
2/1	2026/09/26 19:12	agent	patch-evaluator	1m Model: core Args: null Results: { "EnableConfigs": [ "SYSCTL", "PROC_FS", "SYSVIPC", "POSIX_MQUEUE", "IPC_NS" ], "FocusSymbols": [ "__register_sysctl_table_ctx", "sysctl_apply_ctx", "proc_sys_call_handler", "proc_sys_permission", "sysctl_check_table", "setup_ipc_sysctls", "setup_mq_sysctls" ], "Reasoning": "The patch introduces a new context-based data pointer resolution mechanism for sysctl entries (CTL_TABLE_F_CTX_DATA) to avoid duplicating ctl_tables when instantiating new IPC namespaces. This alters pointer calculation in core sysctl access paths (proc_sys_call_handler, proc_sys_permission) and adds new table validation checks in sysctl_check_table and __register_sysctl_table_ctx. This code is fully reachable via standard unshare(CLONE_NEWIPC) and /proc/sys read/write operations, making it valuable to fuzz for potential out-of-bounds pointer calculation issues or registration inconsistencies.", "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 72956c04a50c26de34979e555c595f8609103b90 Author: syz-cluster <triage@syzkaller.com> Date: Sat Sep 26 19:12:52 2026 +0000 syz-cluster: applied patch under review diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index 04a382178c657..1ed9f4e1a17e2 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -550,12 +550,31 @@ static struct dentry proc_sys_lookup(struct inode dir, struct dentry dentry, return err; } +/ Returns @entry itself when it is not flagged, else a resolved copy in @buf. / +static const struct ctl_table sysctl_apply_ctx(struct ctl_table_header head, + const struct ctl_table entry, + struct ctl_table buf) +{ + ptrdiff_t off; + + if (!(entry->flags & CTL_TABLE_F_CTX_DATA)) + return entry; + + off = (const char )entry->data - (const char )head->ctx.tmpl; + + buf = entry; + buf->data = (char )head->ctx.inst + off; + + return buf; +} + static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter, int write) { struct inode inode = file_inode(iocb->ki_filp); struct ctl_table_header head = grab_header(inode); const struct ctl_table table = PROC_I(inode)->sysctl_entry; + struct ctl_table ctx_entry; size_t count = iov_iter_count(iter); char kbuf; ssize_t error; @@ -567,6 +586,8 @@ static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter, * At this point we know that the sysctl was not unregistered * and won't be until we finish. / + table = sysctl_apply_ctx(head, table, &ctx_entry); + error = -EPERM; if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ)) goto out; @@ -797,6 +818,7 @@ static int proc_sys_permission(struct mnt_idmap idmap, / struct ctl_table_header head; const struct ctl_table table; + struct ctl_table ctx_entry; int error; / Executable files are not allowed under /proc/sys/ / @@ -810,8 +832,11 @@ static int proc_sys_permission(struct mnt_idmap idmap, table = PROC_I(inode)->sysctl_entry; if (!table) /* global root - r-xr-xr-x / error = mask & MAY_WRITE ? -EACCES : 0; - else / Use the permissions on the sysctl table entry / + else { + / ->permissions may inspect the entry, so resolve it first. / + table = sysctl_apply_ctx(head, table, &ctx_entry); error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK); + } sysctl_head_finish(head); return error; @@ -1143,10 +1168,18 @@ static int sysctl_check_table_array(const char path, const struct ctl_table ta static int sysctl_check_table(const char path, struct ctl_table_header header) { const struct ctl_table entry; + u8 flagged = 0; int err = 0; list_for_each_table_entry(entry, header) { if (!entry->procname) err \|= sysctl_err(path, entry, "procname is null"); + if (entry->flags & CTL_TABLE_F_CTX_DATA) { + if (!entry->data) + err \|= sysctl_err(path, entry, "No data to resolve"); + if (!header->ctx.inst \|\| !header->ctx.tmpl) + err \|= sysctl_err(path, entry, "No context to resolve against"); + } + flagged \|= entry->flags & CTL_TABLE_F_CTX; if ((entry->proc_handler == proc_dostring) \|\| (entry->proc_handler == proc_dobool) \|\| (entry->proc_handler == proc_dointvec) \|\| @@ -1173,6 +1206,12 @@ static int sysctl_check_table(const char path, struct ctl_table_header header) err \|= sysctl_err(path, entry, "bogus .mode 0%o", entry->mode); } + /* A context nobody resolves against is a forgotten flag. / + if (!flagged && (header->ctx.inst \|\| header->ctx.tmpl)) { + pr_err("sysctl table check failed: %s context given but no entry is flagged\n", + path); + err = -EINVAL; + } return err; } @@ -1324,7 +1363,7 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) } /** - * __register_sysctl_table - register a leaf sysctl table + * __register_sysctl_table_ctx - register a leaf sysctl table * @set: Sysctl tree to register on * @path: The path to the directory the sysctl table is in. * @@ -1333,6 +1372,9 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) be a global or dynamically allocated by the caller and free'd later * after sysctl unregistration. * @table_size : The number of elements in table + * @ctx: instances that entries flagged CTL_TABLE_F_CTX_* resolve against, see + * struct sysctl_context. Copied, so it may be on stack. %NULL when no + * entry is flagged. * * Register a sysctl table hierarchy. @table should be a filled in ctl_table * array. @@ -1343,6 +1385,7 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) data - a pointer to data for use by proc_handler * maxlen - the maximum size in bytes of the data * mode - the file permissions for the /proc/sys file + * flags - CTL_TABLE_F_* bits naming members to resolve against @ctx * type - Defines the target type (described in struct definition) * proc_handler - the text handler routine (described below) * @@ -1366,9 +1409,10 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) This routine returns %NULL on a failure to register, and a pointer * to the table header on success. / -struct ctl_table_header __register_sysctl_table( +struct ctl_table_header __register_sysctl_table_ctx( struct ctl_table_set set, - const char path, const struct ctl_table table, size_t table_size) + const char path, const struct ctl_table table, size_t table_size, + const struct sysctl_context ctx) { struct ctl_table_root root = set->dir.header.root; struct ctl_table_header header; @@ -1382,6 +1426,8 @@ struct ctl_table_header __register_sysctl_table( node = (struct ctl_node )(header + 1); init_header(header, root, set, node, table, table_size); + if (ctx) + header->ctx = ctx; if (sysctl_check_table(path, header)) goto fail; @@ -1427,7 +1473,7 @@ struct ctl_table_header __register_sysctl_table( Register a sysctl table. @table should be a filled in ctl_table * array. A completely 0 filled entry terminates the table. * - * See __register_sysctl_table for more details. + * See __register_sysctl_table_ctx for more details. / struct ctl_table_header register_sysctl_sz(const char path, const struct ctl_table table, size_t table_size) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index e5d7226ab6f5a..b2c57c530bdc9 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -22,6 +22,8 @@ #ifndef _LINUX_SYSCTL_H #define _LINUX_SYSCTL_H +#include <linux/bits.h> +#include <linux/build_bug.h> #include <linux/list.h> #include <linux/rcupdate.h> #include <linux/wait.h> @@ -224,12 +226,50 @@ struct ctl_table { void data; int maxlen; umode_t mode; + u8 flags; / CTL_TABLE_F_* / proc_handler proc_handler; /* Callback for text formatting / struct ctl_table_poll poll; void extra1; void extra2; } __randomize_layout; +/* + * ctl_table::flags. Resolve the corresponding member against the + * registration context instead of using it as it stands. + / +#define CTL_TABLE_F_CTX_DATA BIT(0) +#define CTL_TABLE_F_CTX CTL_TABLE_F_CTX_DATA + +/* + * struct sysctl_context - ctl_table specific context + * @inst: entry location + * @tmpl: struct template (used to calculate offset into @inst) + * + * @inst/@tmpl pair is used to overlay the ctl_table entry before calling + * proc_handler. This is relevant when struct members (like ->data) are + * somewhere different than the const static ctl_table array (think + * namespaces). Build it with SYSCTL_CTX() so the compiler checks that + * both point at the same type. + / +struct sysctl_context { + void inst; + const void tmpl; +}; + +/* + * SYSCTL_CTX - build a struct sysctl_context + * @_inst: the instance this registration describes + * @_tmpl: the instance the table's data members name + * + * Fails to build unless @_inst and @_tmpl point at the same type. + / +#define SYSCTL_CTX(_inst, _tmpl) \ + ((struct sysctl_context){ \ + .inst = (_inst) + \ + BUILD_BUG_ON_ZERO(!__same_type((_inst), (_tmpl))), \ + .tmpl = (_tmpl), \ + }) + struct ctl_node { struct rb_node node; struct ctl_table_header header; @@ -244,6 +284,7 @@ struct ctl_node { * something is removed from inodes * @nreg: When nreg drops to 0 the ctl_table_header will be unregistered. * @rcu: Delays the freeing of the inode. Introduced with "unfuck proc_sysctl ->d_compare()" + * @ctx: instances given to __register_sysctl_table_ctx(), see struct sysctl_context * * @type: Enumeration to differentiate between ctl target types: * type.SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations @@ -268,6 +309,7 @@ struct ctl_table_header { struct ctl_dir parent; struct ctl_node node; struct hlist_head inodes; /* head for proc_inode->sysctl_inodes / + struct sysctl_context ctx; enum { SYSCTL_TABLE_TYPE_DEFAULT, SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY, @@ -305,9 +347,18 @@ extern void setup_sysctl_set(struct ctl_table_set p, int (is_seen)(struct ctl_table_set )); extern void retire_sysctl_set(struct ctl_table_set set); -struct ctl_table_header __register_sysctl_table( +struct ctl_table_header __register_sysctl_table_ctx( + struct ctl_table_set set, + const char path, const struct ctl_table table, size_t table_size, + const struct sysctl_context ctx); + +static inline struct ctl_table_header __register_sysctl_table( struct ctl_table_set set, - const char path, const struct ctl_table table, size_t table_size); + const char path, const struct ctl_table table, size_t table_size) +{ + return __register_sysctl_table_ctx(set, path, table, table_size, NULL); +} + struct ctl_table_header register_sysctl_sz(const char path, const struct ctl_table table, size_t table_size); void unregister_sysctl_table(struct ctl_table_header * table); diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c index d038d944257f6..5d73487bb81c0 100644 --- a/ipc/ipc_sysctl.c +++ b/ipc/ipc_sysctl.c @@ -13,7 +13,6 @@ #include <linux/capability.h> #include <linux/ipc_namespace.h> #include <linux/msg.h> -#include <linux/slab.h> #include <linux/cred.h> #include "util.h" @@ -79,6 +78,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_ctlmax, .maxlen = sizeof(init_ipc_ns.shm_ctlmax), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_doulongvec_minmax, }, { @@ -86,6 +86,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_ctlall, .maxlen = sizeof(init_ipc_ns.shm_ctlall), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_doulongvec_minmax, }, { @@ -93,6 +94,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_ctlmni, .maxlen = sizeof(init_ipc_ns.shm_ctlmni), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = &ipc_mni, @@ -102,6 +104,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_rmid_forced, .maxlen = sizeof(init_ipc_ns.shm_rmid_forced), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_ipc_dointvec_minmax_orphans, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, @@ -111,6 +114,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.msg_ctlmax, .maxlen = sizeof(init_ipc_ns.msg_ctlmax), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -120,6 +124,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.msg_ctlmni, .maxlen = sizeof(init_ipc_ns.msg_ctlmni), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = &ipc_mni, @@ -138,6 +143,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.msg_ctlmnb, .maxlen = sizeof(init_ipc_ns.msg_ctlmnb), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -147,6 +153,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.sem_ctls, .maxlen = 4sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_ipc_sem_dointvec, }, #ifdef CONFIG_CHECKPOINT_RESTORE @@ -155,6 +162,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.ids[IPC_SEM_IDS].next_id, .maxlen = sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id), .mode = 0444, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -164,6 +172,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.ids[IPC_MSG_IDS].next_id, .maxlen = sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id), .mode = 0444, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -173,6 +182,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.ids[IPC_SHM_IDS].next_id, .maxlen = sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id), .mode = 0444, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -244,57 +254,15 @@ static struct ctl_table_root set_root = { bool setup_ipc_sysctls(struct ipc_namespace ns) { - struct ctl_table tbl; + struct sysctl_context ctx = SYSCTL_CTX(ns, &init_ipc_ns); setup_sysctl_set(&ns->ipc_set, &set_root, set_is_seen); - tbl = kmemdup(ipc_sysctls, sizeof(ipc_sysctls), GFP_KERNEL); - if (tbl) { - int i; - - for (i = 0; i < ARRAY_SIZE(ipc_sysctls); i++) { - if (tbl[i].data == &init_ipc_ns.shm_ctlmax) - tbl[i].data = &ns->shm_ctlmax; - - else if (tbl[i].data == &init_ipc_ns.shm_ctlall) - tbl[i].data = &ns->shm_ctlall; - - else if (tbl[i].data == &init_ipc_ns.shm_ctlmni) - tbl[i].data = &ns->shm_ctlmni; - - else if (tbl[i].data == &init_ipc_ns.shm_rmid_forced) - tbl[i].data = &ns->shm_rmid_forced; - - else if (tbl[i].data == &init_ipc_ns.msg_ctlmax) - tbl[i].data = &ns->msg_ctlmax; - - else if (tbl[i].data == &init_ipc_ns.msg_ctlmni) - tbl[i].data = &ns->msg_ctlmni; - - else if (tbl[i].data == &init_ipc_ns.msg_ctlmnb) - tbl[i].data = &ns->msg_ctlmnb; - - else if (tbl[i].data == &init_ipc_ns.sem_ctls) - tbl[i].data = &ns->sem_ctls; -#ifdef CONFIG_CHECKPOINT_RESTORE - else if (tbl[i].data == &init_ipc_ns.ids[IPC_SEM_IDS].next_id) - tbl[i].data = &ns->ids[IPC_SEM_IDS].next_id; - - else if (tbl[i].data == &init_ipc_ns.ids[IPC_MSG_IDS].next_id) - tbl[i].data = &ns->ids[IPC_MSG_IDS].next_id; - - else if (tbl[i].data == &init_ipc_ns.ids[IPC_SHM_IDS].next_id) - tbl[i].data = &ns->ids[IPC_SHM_IDS].next_id; -#endif - else - tbl[i].data = NULL; - } - - ns->ipc_sysctls = __register_sysctl_table(&ns->ipc_set, "kernel", tbl, - ARRAY_SIZE(ipc_sysctls)); - } + ns->ipc_sysctls = __register_sysctl_table_ctx(&ns->ipc_set, "kernel", + ipc_sysctls, + ARRAY_SIZE(ipc_sysctls), + &ctx); if (!ns->ipc_sysctls) { - kfree(tbl); retire_sysctl_set(&ns->ipc_set); return false; } @@ -304,12 +272,8 @@ bool setup_ipc_sysctls(struct ipc_namespace ns) void retire_ipc_sysctls(struct ipc_namespace ns) { - const struct ctl_table tbl; - - tbl = ns->ipc_sysctls->ctl_table_arg; unregister_sysctl_table(ns->ipc_sysctls); retire_sysctl_set(&ns->ipc_set); - kfree(tbl); } static int __init ipc_sysctl_init(void) diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c index 0dd12e1c9f53e..9919e2d3a11a4 100644 --- a/ipc/mq_sysctl.c +++ b/ipc/mq_sysctl.c @@ -11,7 +11,6 @@ #include <linux/stat.h> #include <linux/capability.h> -#include <linux/slab.h> #include <linux/cred.h> static int msg_max_limit_min = MIN_MSGMAX; @@ -26,6 +25,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_queues_max, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec, }, { @@ -33,6 +33,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msg_max, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_max_limit_min, .extra2 = &msg_max_limit_max, @@ -42,6 +43,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msgsize_max, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_maxsize_limit_min, .extra2 = &msg_maxsize_limit_max, @@ -51,6 +53,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msg_default, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_max_limit_min, .extra2 = &msg_max_limit_max, @@ -60,6 +63,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msgsize_default, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_maxsize_limit_min, .extra2 = &msg_maxsize_limit_max, @@ -116,39 +120,15 @@ static struct ctl_table_root set_root = { bool setup_mq_sysctls(struct ipc_namespace ns) { - struct ctl_table tbl; + struct sysctl_context ctx = SYSCTL_CTX(ns, &init_ipc_ns); setup_sysctl_set(&ns->mq_set, &set_root, set_is_seen); - tbl = kmemdup(mq_sysctls, sizeof(mq_sysctls), GFP_KERNEL); - if (tbl) { - int i; - - for (i = 0; i < ARRAY_SIZE(mq_sysctls); i++) { - if (tbl[i].data == &init_ipc_ns.mq_queues_max) - tbl[i].data = &ns->mq_queues_max; - - else if (tbl[i].data == &init_ipc_ns.mq_msg_max) - tbl[i].data = &ns->mq_msg_max; - - else if (tbl[i].data == &init_ipc_ns.mq_msgsize_max) - tbl[i].data = &ns->mq_msgsize_max; - - else if (tbl[i].data == &init_ipc_ns.mq_msg_default) - tbl[i].data = &ns->mq_msg_default; - - else if (tbl[i].data == &init_ipc_ns.mq_msgsize_default) - tbl[i].data = &ns->mq_msgsize_default; - else - tbl[i].data = NULL; - } - - ns->mq_sysctls = __register_sysctl_table(&ns->mq_set, - "fs/mqueue", tbl, - ARRAY_SIZE(mq_sysctls)); - } + ns->mq_sysctls = __register_sysctl_table_ctx(&ns->mq_set, "fs/mqueue", + mq_sysctls, + ARRAY_SIZE(mq_sysctls), + &ctx); if (!ns->mq_sysctls) { - kfree(tbl); retire_sysctl_set(&ns->mq_set); return false; } @@ -158,10 +138,6 @@ bool setup_mq_sysctls(struct ipc_namespace ns) void retire_mq_sysctls(struct ipc_namespace ns) { - const struct ctl_table *tbl; - - tbl = ns->mq_sysctls->ctl_table_arg; unregister_sysctl_table(ns->mq_sysctls); retire_sysctl_set(&ns->mq_set); - kfree(tbl); }
3/2	2026/09/26 19:12	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10637 output: 35 thoughts: 867 Thoughts: Analyzing a Git Commit for Syzkaller Fuzzing Potential Okay, so I need to evaluate this git commit for its suitability for syzkaller fuzzing. Let's break it down. The patch touches several files: `fs/proc/proc_sysctl.c`, `include/linux/sysctl.h`, `ipc/ipc_sysctl.c`, and `ipc/mq_sysctl.c`. My initial thought is that this has the potential to impact a few critical areas. First, I see changes within `fs/proc/proc_sysctl.c`. The introduction of `sysctl_apply_ctx` is interesting and will need a closer look. It seems to handle context-aware sysctl table application. The modification of `proc_sys_call_handler`, `proc_sys_permission`, and `sysctl_check_table` to incorporate this new context handling further reinforces this. It's also replacing `__register_sysctl_table` with `__register_sysctl_table_ctx`, taking a `const struct sysctl_context *ctx` as an argument. Context is key! The commit also modifies `ipc/ipc_sysctl.c` and `ipc/mq_sysctl.c`. It seems to be refactoring how sysctls for IPC namespaces are handled. Instead of duplicating the `ipc_sysctls` and `mq_sysctls` tables, it's now using a context-aware approach (`CTL_TABLE_F_CTX_DATA`) and passing `struct sysctl_context ctx = SYSCTL_CTX(ns, &init_ipc_ns);` to `__register_sysctl_table_ctx`. This is likely an optimization to avoid some memory overhead. Now, based on my understanding of syzkaller's philosophy, I need to evaluate its reachability. Is this new code reachable in standard virtualized environments (GCE or QEMU)? Absolutely! Unsharing namespaces (`CLONE_NEWIPC`) and accessing sysctl entries in `/proc/sys/kernel/` or `/proc/sys/fs/mqueue/` are standard and well-fuzzed by syzkaller. Looking at the core subsystems criteria, `fs/proc/proc_sysctl.c` is definitely involved in core VFS, procfs, and sysctl handling. This immediately piques my interest. The commit also clearly falls under the "Refactorings and Code Cleanups" category, and syzkaller's documentation rightly reminds us that "REFACTORING" claims need to be carefully examined. Any reachable executable code that is modified or refactored MUST be fuzzed! Therefore, I'm confident that this is worth fuzzing. My next step is to determine the necessary configurations. I need to figure out which kernel configuration options (`Kconfigs`) control the relevant code paths in `ipc_sysctl.c`, `mq_sysctl.c`, and `proc_sysctl.c`. Time to use `grepper` or check the relevant Makefiles to identify the controlling configuration options.
4/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "ipc_sysctl\|mq_sysctl\|proc_sysctl", "PathPrefix": "ipc" } Results: { "Output": "ipc/Makefile=7=obj-$(CONFIG_SYSVIPC) += util.o msgutil.o msg.o sem.o shm.o syscall.o\nipc/Makefile:8:obj-$(CONFIG_SYSVIPC_SYSCTL) += ipc_sysctl.o\nipc/Makefile-9-obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o\nipc/Makefile=10=obj-$(CONFIG_IPC_NS) += namespace.o\nipc/Makefile:11:obj-$(CONFIG_POSIX_MQUEUE_SYSCTL) += mq_sysctl.o\nipc/Makefile-12-\n--\nipc/ipc_sysctl.c=73=int ipc_min_cycle = RADIX_TREE_MAP_SIZE;\nipc/ipc_sysctl.c-74-\nipc/ipc_sysctl.c:75:static const struct ctl_table ipc_sysctls[] = {\nipc/ipc_sysctl.c-76-\t{\n--\nipc/ipc_sysctl.c=249=static struct ctl_table_root set_root = {\n--\nipc/ipc_sysctl.c-254-\nipc/ipc_sysctl.c:255:bool setup_ipc_sysctls(struct ipc_namespace ns)\nipc/ipc_sysctl.c-256-{\n--\nipc/ipc_sysctl.c-260-\nipc/ipc_sysctl.c:261:\tns-\u003eipc_sysctls = __register_sysctl_table_ctx(\u0026ns-\u003eipc_set, \"kernel\",\nipc/ipc_sysctl.c:262:\t\t\t\t\t\t ipc_sysctls,\nipc/ipc_sysctl.c:263:\t\t\t\t\t\t ARRAY_SIZE(ipc_sysctls),\nipc/ipc_sysctl.c-264-\t\t\t\t\t\t \u0026ctx);\nipc/ipc_sysctl.c:265:\tif (!ns-\u003eipc_sysctls) {\nipc/ipc_sysctl.c-266-\t\tretire_sysctl_set(\u0026ns-\u003eipc_set);\n--\nipc/ipc_sysctl.c-272-\nipc/ipc_sysctl.c:273:void retire_ipc_sysctls(struct ipc_namespace ns)\nipc/ipc_sysctl.c-274-{\nipc/ipc_sysctl.c:275:\tunregister_sysctl_table(ns-\u003eipc_sysctls);\nipc/ipc_sysctl.c-276-\tretire_sysctl_set(\u0026ns-\u003eipc_set);\n--\nipc/ipc_sysctl.c-278-\nipc/ipc_sysctl.c:279:static int __init ipc_sysctl_init(void)\nipc/ipc_sysctl.c-280-{\nipc/ipc_sysctl.c:281:\tif (!setup_ipc_sysctls(\u0026init_ipc_ns)) {\nipc/ipc_sysctl.c-282-\t\tpr_warn(\"ipc sysctl registration failed\\n\");\n--\nipc/ipc_sysctl.c-287-\nipc/ipc_sysctl.c:288:device_initcall(ipc_sysctl_init);\nipc/ipc_sysctl.c-289-\n--\nipc/mq_sysctl.c=20=static int msg_maxsize_limit_max = HARD_MSGSIZEMAX;\nipc/mq_sysctl.c-21-\nipc/mq_sysctl.c:22:static const struct ctl_table mq_sysctls[] = {\nipc/mq_sysctl.c-23-\t{\n--\nipc/mq_sysctl.c=115=static struct ctl_table_root set_root = {\n--\nipc/mq_sysctl.c-120-\nipc/mq_sysctl.c:121:bool setup_mq_sysctls(struct ipc_namespace ns)\nipc/mq_sysctl.c-122-{\n--\nipc/mq_sysctl.c-126-\nipc/mq_sysctl.c:127:\tns-\u003emq_sysctls = __register_sysctl_table_ctx(\u0026ns-\u003emq_set, \"fs/mqueue\",\nipc/mq_sysctl.c:128:\t\t\t\t\t\t mq_sysctls,\nipc/mq_sysctl.c:129:\t\t\t\t\t\t ARRAY_SIZE(mq_sysctls),\nipc/mq_sysctl.c-130-\t\t\t\t\t\t \u0026ctx);\nipc/mq_sysctl.c:131:\tif (!ns-\u003emq_sysctls) {\nipc/mq_sysctl.c-132-\t\tretire_sysctl_set(\u0026ns-\u003emq_set);\n--\nipc/mq_sysctl.c-138-\nipc/mq_sysctl.c:139:void retire_mq_sysctls(struct ipc_namespace ns)\nipc/mq_sysctl.c-140-{\nipc/mq_sysctl.c:141:\tunregister_sysctl_table(ns-\u003emq_sysctls);\nipc/mq_sysctl.c-142-\tretire_sysctl_set(\u0026ns-\u003emq_set);\n--\nipc/mqueue.c=1642=static int __init init_mqueue_fs(void)\n--\nipc/mqueue.c-1651-\nipc/mqueue.c:1652:\tif (!setup_mq_sysctls(\u0026init_ipc_ns)) {\nipc/mqueue.c-1653-\t\tpr_warn(\"sysctl registration failed\\n\");\n--\nipc/mqueue.c-1672-out_sysctl:\nipc/mqueue.c:1673:\tretire_mq_sysctls(\u0026init_ipc_ns);\nipc/mqueue.c-1674-out_kmem:\n--\nipc/namespace.c=39=static struct ipc_namespace create_ipc_ns(struct user_namespace user_ns,\n--\nipc/namespace.c-77-\terr = -ENOMEM;\nipc/namespace.c:78:\tif (!setup_mq_sysctls(ns))\nipc/namespace.c-79-\t\tgoto fail_mq_mount;\nipc/namespace.c-80-\nipc/namespace.c:81:\tif (!setup_ipc_sysctls(ns))\nipc/namespace.c:82:\t\tgoto fail_mq_sysctls;\nipc/namespace.c-83-\n--\nipc/namespace.c-94-fail_ipc:\nipc/namespace.c:95:\tretire_ipc_sysctls(ns);\nipc/namespace.c:96:fail_mq_sysctls:\nipc/namespace.c:97:\tretire_mq_sysctls(ns);\nipc/namespace.c-98-fail_mq_mount:\n--\nipc/namespace.c=150=static void free_ipc_ns(struct ipc_namespace *ns)\n--\nipc/namespace.c-160-\nipc/namespace.c:161:\tretire_mq_sysctls(ns);\nipc/namespace.c:162:\tretire_ipc_sysctls(ns);\nipc/namespace.c-163-\n" }
5/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 13996 output: 44 thoughts: 29 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Examining System Control Configuration Options Alright, let's dive in. First, I need to verify how these system control options are configured. Specifically, I'm thinking about `SYSVIPC_SYSCTL`, `POSIX_MQUEUE_SYSCTL`, and `PROC_SYSCTL`. These are the key pieces that control whether the system interfaces for SysV IPC, POSIX message queues, and the proc filesystem's control interface, respectively, are exposed via the `sysctl` interface. I want to check their status in the Kconfig. This is an important step; if they're not enabled, or not enabled in the way I expect, it could affect a number of potential debugging and feature-implementing that I am about to look into. I’m thinking about this because I need to trace and understand specific interactions with system resources. This is a critical first step. I need to make sure I understand the base-level configuration before proceeding.
6/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "config (SYSVIPC_SYSCTL\|POSIX_MQUEUE_SYSCTL\|PROC_SYSCTL)", "PathPrefix": "init/" } Results: { "Output": "init/Kconfig=470=config SYSVIPC\n--\ninit/Kconfig-484-\ninit/Kconfig:485:config SYSVIPC_SYSCTL\ninit/Kconfig-486-\tbool\n--\ninit/Kconfig=495=config POSIX_MQUEUE\n--\ninit/Kconfig-510-\ninit/Kconfig:511:config POSIX_MQUEUE_SYSCTL\ninit/Kconfig-512-\tbool\n" }
7/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14415 output: 38 thoughts: 29 Thoughts: Okay, here's my attempt at summarizing my thought process, keeping in mind the user is an expert: Investigating SYSVIPC and POSIX Message Queue Configuration Alright, let's dive into this. I need to understand how `SYSVIPC_SYSCTL` and `POSIX_MQUEUE_SYSCTL` are being handled within the kernel configuration system, specifically in `init/Kconfig`. This means I want to see how these options are selected or defined within the Kconfig hierarchy. Are they direct dependencies, tristates, or are they being chosen based on some other condition, maybe architectural specifics or feature enablement? What's the overall picture of their relationships to other kernel features? This is crucial for understanding how these system calls are exposed or hidden, and how a developer could potentially tweak their usage. I'm going to look for the precise selection and definition logic to get the full picture.
8/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "(SYSVIPC_SYSCTL\|POSIX_MQUEUE_SYSCTL)", "PathPrefix": "init/" } Results: { "Output": "init/Kconfig=470=config SYSVIPC\n--\ninit/Kconfig-484-\ninit/Kconfig:485:config SYSVIPC_SYSCTL\ninit/Kconfig-486-\tbool\n--\ninit/Kconfig=495=config POSIX_MQUEUE\n--\ninit/Kconfig-510-\ninit/Kconfig:511:config POSIX_MQUEUE_SYSCTL\ninit/Kconfig-512-\tbool\n" }
9/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14801 output: 20 thoughts: 23 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Investigating SYSVIPC_SYSCTL Configuration Okay, so I need to track down the configuration definition for `SYSVIPC_SYSCTL`. My gut feeling, as usual, tells me to start poking around in the kernel's Kconfig files. Specifically, I'm going to head for the `fs/proc/Kconfig` file first. That's a logical starting point given its focus on the `/proc` filesystem and related system parameters, but it could be anywhere. I'll also do a quick grep and hunt for where it's selected if it's not actually defined in that location, since the Kconfig system is built around dependencies. If I can nail down the direct definition or selection, I can get a clearer picture of its dependencies and how it's intended to be used. Let's dig in.
10/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "SYSVIPC_SYSCTL" } Results: { "Output": "include/linux/ipc_namespace.h=194=static inline bool setup_mq_sysctls(struct ipc_namespace ns)\n--\ninclude/linux/ipc_namespace.h-200-\ninclude/linux/ipc_namespace.h:201:#ifdef CONFIG_SYSVIPC_SYSCTL\ninclude/linux/ipc_namespace.h-202-\n--\ninclude/linux/ipc_namespace.h=204=void retire_ipc_sysctls(struct ipc_namespace ns);\ninclude/linux/ipc_namespace.h-205-\ninclude/linux/ipc_namespace.h:206:#else /* CONFIG_SYSVIPC_SYSCTL /\ninclude/linux/ipc_namespace.h-207-\n--\ninclude/linux/ipc_namespace.h=212=static inline bool setup_ipc_sysctls(struct ipc_namespace ns)\n--\ninclude/linux/ipc_namespace.h-216-\ninclude/linux/ipc_namespace.h:217:#endif /* CONFIG_SYSVIPC_SYSCTL /\ninclude/linux/ipc_namespace.h-218-#endif\n--\ninit/Kconfig=470=config SYSVIPC\n--\ninit/Kconfig-484-\ninit/Kconfig:485:config SYSVIPC_SYSCTL\ninit/Kconfig-486-\tbool\n--\nipc/Makefile=7=obj-$(CONFIG_SYSVIPC) += util.o msgutil.o msg.o sem.o shm.o syscall.o\nipc/Makefile:8:obj-$(CONFIG_SYSVIPC_SYSCTL) += ipc_sysctl.o\nipc/Makefile-9-obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o\n--\nipc/util.h-34-\nipc/util.h:35:#ifdef CONFIG_SYSVIPC_SYSCTL\nipc/util.h-36-extern int ipc_mni;\n--\nipc/util.h=38=extern int ipc_min_cycle;\n--\nipc/util.h-42-\nipc/util.h:43:#else / CONFIG_SYSVIPC_SYSCTL /\nipc/util.h-44-\n--\nipc/util.h-48-#define IPCMNI_IDX_MASK\t\t((1 \u003c\u003c IPCMNI_SHIFT) - 1)\nipc/util.h:49:#endif / CONFIG_SYSVIPC_SYSCTL */\nipc/util.h-50-\n" }
11/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15650 output: 32 thoughts: 19 Thoughts: Okay, here's the summary, rendered as if it's my own thought process: Diving into init/Kconfig: A Specific Section Needs Scrutiny Alright, I'm heading straight for the heart of the matter – specifically, lines 470 through 520 of `init/Kconfig`. This section feels like the key, the fulcrum of whatever problem I'm trying to solve. I need to understand the configuration options defined here thoroughly; any small detail could hold the answer I need. I'm hoping to understand exactly what these lines control and how they interact with other parts of the system. I'll read with a critical eye, looking for dependencies, default values, and potential conflicts. This is where the subtleties often hide, and I need to be as precise as possible. Let's get to it.
12/2	2026/09/26 19:13	tool	read-file	0m Args: { "File": "init/Kconfig", "FirstLine": 470, "LineCount": 55 } Results: { "Contents": " 470:\tconfig SYSVIPC\n 471:\t\tbool \"System V IPC\"\n 472:\t\thelp\n 473:\t\t Inter Process Communication is a suite of library functions and\n 474:\t\t system calls which let processes (running programs) synchronize and\n 475:\t\t exchange information. It is generally considered to be a good thing,\n 476:\t\t and some programs won't run unless you say Y here. In particular, if\n 477:\t\t you want to run the DOS emulator dosemu under Linux (read the\n 478:\t\t DOSEMU-HOWTO, available from \u003chttp://www.tldp.org/docs.html#howto\u003e),\n 479:\t\t you'll need to say Y here.\n 480:\t\n 481:\t\t You can find documentation about IPC with \"info ipc\" and also in\n 482:\t\t section 6.4 of the Linux Programmer's Guide, available from\n 483:\t\t \u003chttp://www.tldp.org/guides.html\u003e.\n 484:\t\n 485:\tconfig SYSVIPC_SYSCTL\n 486:\t\tbool\n 487:\t\tdepends on SYSVIPC\n 488:\t\tdepends on SYSCTL\n 489:\t\tdefault y\n 490:\t\n 491:\tconfig SYSVIPC_COMPAT\n 492:\t\tdef_bool y\n 493:\t\tdepends on COMPAT \u0026\u0026 SYSVIPC\n 494:\t\n 495:\tconfig POSIX_MQUEUE\n 496:\t\tbool \"POSIX Message Queues\"\n 497:\t\tdepends on NET\n 498:\t\thelp\n 499:\t\t POSIX variant of message queues is a part of IPC. In POSIX message\n 500:\t\t queues every message has a priority which decides about succession\n 501:\t\t of receiving it by a process. If you want to compile and run\n 502:\t\t programs written e.g. for Solaris with use of its POSIX message\n 503:\t\t queues (functions mq_*) say Y here.\n 504:\t\n 505:\t\t POSIX message queues are visible as a filesystem called 'mqueue'\n 506:\t\t and can be mounted somewhere if you want to do filesystem\n 507:\t\t operations on message queues.\n 508:\t\n 509:\t\t If unsure, say Y.\n 510:\t\n 511:\tconfig POSIX_MQUEUE_SYSCTL\n 512:\t\tbool\n 513:\t\tdepends on POSIX_MQUEUE\n 514:\t\tdepends on SYSCTL\n 515:\t\tdefault y\n 516:\t\n 517:\tconfig WATCH_QUEUE\n 518:\t\tbool \"General notification queue\"\n 519:\t\tdefault n\n 520:\t\thelp\n 521:\t\n 522:\t\t This is a general notification queue for the kernel to pass events to\n 523:\t\t userspace by splicing them into pipes. It can be used in conjunction\n 524:\t\t with watches for key/keyring change notifications and device\n" }
13/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16687 output: 27 thoughts: 119 Thoughts: Okay, here's my breakdown of what's going on, thinking it through from a kernel expert's perspective: Kernel Configuration Dependencies and Namespace Setup Right, so I'm looking at these configuration options, `SYSVIPC_SYSCTL` and `POSIX_MQUEUE_SYSCTL`. They're both configured as 'y' by default. But what's really important is that their dependencies are pretty clear: `SYSVIPC_SYSCTL` needs both `SYSVIPC` and `SYSCTL` to be set, and `POSIX_MQUEUE_SYSCTL` relies on `POSIX_MQUEUE` and `SYSCTL`. That seems straightforward enough. Then I see the connection to `setup_ipc_sysctls(ns)` and `setup_mq_sysctls(ns)`. These functions are called when an IPC namespace is created. That tells me that's where the actual system control interface for these IPC mechanisms is set up, and of course `CONFIG_IPC_NS` is a prerequisite for that functionality to exist in the first place. This makes sense: namespaces and IPC go hand in hand. So, where are the system control calls defined? Looks like `proc_sysctl.c` might be the place. Okay, I need to check what actually enables that code. I need to dive into `fs/proc/proc_sysctl.c` to understand that part of the picture. That will help me connect the dots between the configuration options, the namespace setup, and the actual system control implementation.
14/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "proc_sysctl", "PathPrefix": "fs/proc" } Results: { "Output": "fs/proc/Makefile=31=proc-y\t+= thread_self.o\nfs/proc/Makefile:32:proc-$(CONFIG_SYSCTL)\t\t+= proc_sysctl.o\nfs/proc/Makefile-33-proc-$(CONFIG_NET)\t\t+= proc_net.o\n--\nfs/proc/internal.h=349=extern void proc_thread_self_init(void);\n--\nfs/proc/internal.h-351-/\nfs/proc/internal.h:352: proc_sysctl.c\nfs/proc/internal.h-353- */\n" }
15/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17319 output: 23 thoughts: 376 Thoughts: My Assessment of Kernel Configuration and System Calls Okay, so I'm looking at kernel configuration options, specifically `CONFIG_PROC_FS` and `CONFIG_SYSCTL`. Then, I'm noting the related options: `CONFIG_SYSVIPC`, `CONFIG_POSIX_MQUEUE`, and `CONFIG_IPC_NS`. I want to cover all bases, so I'll also glance at `CONFIG_CHECKPOINT_RESTORE` to see if it introduces any relevant dependencies. Hmm, looking at the code snippet, it seems like `CHECKPOINT_RESTORE` adds an entry, but it's not strictly required for the core functionality I'm focused on. It's just an extra. Next, I need to understand what's modified or added by these configurations. I'm drilling down into `fs/proc/proc_sysctl.c`. I see a static helper function, `sysctl_apply_ctx`. Also `proc_sys_call_handler`, a file operations callback for proc sysctl files (read_iter/write_iter). There's `proc_sys_permission`, which is an inode operation permission callback. Important too is `sysctl_check_table` for checks at registration time. And finally, there's `__register_sysctl_table_ctx`, an internal or exported registration function. Now I need to determine if this registration function is exposed via an export, or declared in a header. That's the key to understanding how these changes affect the larger system.
16/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "__register_sysctl_table_ctx" } Results: { "Output": "fs/proc/proc_sysctl.c=1337=static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path)\n--\nfs/proc/proc_sysctl.c-1365-/\nfs/proc/proc_sysctl.c:1366: __register_sysctl_table_ctx - register a leaf sysctl table\nfs/proc/proc_sysctl.c-1367- * @set: Sysctl tree to register on\n--\nfs/proc/proc_sysctl.c-1411- /\nfs/proc/proc_sysctl.c:1412:struct ctl_table_header __register_sysctl_table_ctx(\nfs/proc/proc_sysctl.c-1413-\tstruct ctl_table_set set,\n--\nfs/proc/proc_sysctl.c-1475- \nfs/proc/proc_sysctl.c:1476: * See __register_sysctl_table_ctx for more details.\nfs/proc/proc_sysctl.c-1477- /\n--\ninclude/linux/sysctl.h=273=struct ctl_node {\n--\ninclude/linux/sysctl.h-286- @rcu: Delays the freeing of the inode. Introduced with \"unfuck proc_sysctl -\u003ed_compare()\"\ninclude/linux/sysctl.h:287: * @ctx: instances given to __register_sysctl_table_ctx(), see struct sysctl_context\ninclude/linux/sysctl.h-288- \n--\ninclude/linux/sysctl.h=348=extern void retire_sysctl_set(struct ctl_table_set set);\ninclude/linux/sysctl.h-349-\ninclude/linux/sysctl.h:350:struct ctl_table_header __register_sysctl_table_ctx(\ninclude/linux/sysctl.h-351-\tstruct ctl_table_set set,\n--\ninclude/linux/sysctl.h=355=static inline struct ctl_table_header __register_sysctl_table(\n--\ninclude/linux/sysctl.h-358-{\ninclude/linux/sysctl.h:359:\treturn __register_sysctl_table_ctx(set, path, table, table_size, NULL);\ninclude/linux/sysctl.h-360-}\n--\nipc/ipc_sysctl.c=255=bool setup_ipc_sysctls(struct ipc_namespace ns)\n--\nipc/ipc_sysctl.c-260-\nipc/ipc_sysctl.c:261:\tns-\u003eipc_sysctls = __register_sysctl_table_ctx(\u0026ns-\u003eipc_set, \"kernel\",\nipc/ipc_sysctl.c-262-\t\t\t\t\t\t ipc_sysctls,\n--\nipc/mq_sysctl.c=121=bool setup_mq_sysctls(struct ipc_namespace *ns)\n--\nipc/mq_sysctl.c-126-\nipc/mq_sysctl.c:127:\tns-\u003emq_sysctls = __register_sysctl_table_ctx(\u0026ns-\u003emq_set, \"fs/mqueue\",\nipc/mq_sysctl.c-128-\t\t\t\t\t\t mq_sysctls,\n" }
17/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18889 output: 38 thoughts: 593 Thoughts: Analyzing the Sysctl Context for System Call Handling Okay, let's dive into this. I need to understand how these sysctl interfaces function, particularly how context is handled. My initial focus is on the registration and de-registration process. I'll start by checking `ipc/ipc_sysctl.c` and confirm that `setup_ipc_sysctls` and `retire_ipc_sysctls` are the relevant functions. Similarly, I'll examine `ipc/mq_sysctl.c` to look at `setup_mq_sysctls` and `retire_mq_sysctls`. Then I'll expand the investigation to `fs/proc/proc_sysctl.c`. Within that file I see `__register_sysctl_table_ctx`, `sysctl_apply_ctx`, `proc_sys_call_handler`, `proc_sys_permission`, and `sysctl_check_table`. Alright, the core of the matter seems to be in `sysctl_apply_ctx`. Let's scrutinize this function: ```c static const struct ctl_table sysctl_apply_ctx(struct ctl_table_header head, const struct ctl_table entry, struct ctl_table buf) { ptrdiff_t off; if (!(entry->flags & CTL_TABLE_F_CTX_DATA)) return entry; off = (const char )entry->data - (const char )head->ctx.tmpl; buf = entry; buf->data = (char )head->ctx.inst + off; return buf; } ``` Okay, so if the `CTL_TABLE_F_CTX_DATA` flag is set, it calculates an offset (`off`) between the `entry->data` and the `head->ctx.tmpl`. It then copies the entry into a buffer (`buf`) and adjusts the `data` pointer of `buf` using the calculated offset relative to `head->ctx.inst`. This suggests some form of context-specific data mapping or relocation. Now, let's look at how `proc_sys_call_handler` interacts with `sysctl_apply_ctx`: ```c static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter, int write) { struct inode inode = file_inode(iocb->ki_filp); struct ctl_table_header head = grab_header(inode); const struct ctl_table table = PROC_I(inode)->sysctl_entry; struct ctl_table ctx_entry; size_t count = iov_iter_count(iter); char kbuf; ssize_t error; if (IS_ERR(head)) return PTR_ERR(head); / * At this point we know that the sysctl was not unregistered * and won't be until we finish. */ table = sysctl_apply_ctx(head, table, &ctx_entry); error = -EPERM; if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ)) goto out; ... ``` Right, it grabs the `ctl_table_header` and then retrieves the entry. Crucially, it then calls `sysctl_apply_ctx` to modify the `table` pointer. The resulting `table` is then passed to `sysctl_perm`. This means the `table` that ends up being checked for permissions has been potentially modified by applying context. I need to trace exactly how the `table` variable changes within `proc_sys_call_handler`. This seems to be the critical point where context is applied to the sysctl table entry.
18/2	2026/09/26 19:13	tool	read-file	0m Args: { "File": "fs/proc/proc_sysctl.c", "FirstLine": 585, "LineCount": 45 } Results: { "Contents": " 585:\t\t/\n 586:\t\t At this point we know that the sysctl was not unregistered\n 587:\t\t * and won't be until we finish.\n 588:\t\t /\n 589:\t\ttable = sysctl_apply_ctx(head, table, \u0026ctx_entry);\n 590:\t\n 591:\t\terror = -EPERM;\n 592:\t\tif (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))\n 593:\t\t\tgoto out;\n 594:\t\n 595:\t\t/ if that can happen at all, it should be -EINVAL, not -EISDIR /\n 596:\t\terror = -EINVAL;\n 597:\t\tif (!table-\u003eproc_handler)\n 598:\t\t\tgoto out;\n 599:\t\n 600:\t\t/ don't even try if the size is too large /\n 601:\t\terror = -ENOMEM;\n 602:\t\tif (count \u003e= KMALLOC_MAX_SIZE)\n 603:\t\t\tgoto out;\n 604:\t\tkbuf = kvzalloc(count + 1, GFP_KERNEL);\n 605:\t\tif (!kbuf)\n 606:\t\t\tgoto out;\n 607:\t\n 608:\t\tif (write) {\n 609:\t\t\terror = -EFAULT;\n 610:\t\t\tif (!copy_from_iter_full(kbuf, count, iter))\n 611:\t\t\t\tgoto out_free_buf;\n 612:\t\t\tkbuf[count] = '\\0';\n 613:\t\t}\n 614:\t\n 615:\t\terror = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, \u0026kbuf, \u0026count,\n 616:\t\t\t\t\t\t \u0026iocb-\u003eki_pos);\n 617:\t\tif (error)\n 618:\t\t\tgoto out_free_buf;\n 619:\t\n 620:\t\t/ careful: calling conventions are nasty here */\n 621:\t\terror = table-\u003eproc_handler(table, write, kbuf, \u0026count, \u0026iocb-\u003eki_pos);\n 622:\t\tif (error)\n 623:\t\t\tgoto out_free_buf;\n 624:\t\n 625:\t\tif (!write) {\n 626:\t\t\terror = -EFAULT;\n 627:\t\t\tif (copy_to_iter(kbuf, count, iter) \u003c count)\n 628:\t\t\t\tgoto out_free_buf;\n 629:\t\t}\n" }
19/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21057 output: 19 thoughts: 697 Thoughts: My Assessment: A Deep Dive into Potential Sysctl Vulnerabilities Okay, this is interesting. I'm seeing a connection between core sysctl infrastructure and the handling of IPC sysctls, particularly when new IPC namespaces are being created. Let's break this down... My focus is on the `sysctl_apply_ctx` function, specifically how it's used with `proc_handler` and `proc_sys_permission`. I'm noting that the `table` variable, which appears to be a crucial data structure for sysctl entries, gets modified to point to an offset within the context structure. It looks like `table->data` is being re-assigned based on calculations involving `head->ctx.inst`, `off`, and the original data pointer. And, looking at the code, if `entry->flags` has `CTL_TABLE_F_CTX_DATA` set, there are checks related to `entry->data`, `header->ctx.inst`, and `header->ctx.tmpl`. I'm starting to get a sense of how these context-dependent pointers are being resolved, which is key. The possibility of pointer calculation bugs, like negative or out-of-bounds offsets, struct layout mismatches, alignment problems, or even potential lifetime issues, immediately flags this as a critical area. Any miscalculation here could lead to severe kernel memory corruption or an information leak, and I want to investigate thoroughly! Now, the crucial question is reachability, and it appears we have that! Standard syzkaller, the fuzzer that many of us rely on, is creating user namespaces and unsharing IPC namespaces using CLONE_NEWIPC, and then interacting with /proc/sys/kernel/shmmax, msgmax, sem, and similar entries, as well as /proc/sys/fs/mqueue/* . This triggers the problematic functions I mentioned, so this code path is definitely active and being used! This means that `proc_sys_call_handler`, `proc_sys_permission` and especially `sysctl_apply_ctx` are actually being executed within the context of IPC namespaces, making the potential problems far more likely. I've also reviewed the triage instructions and, based on the reachability, the fact that we're looking at a refactoring and semantic change in how per-namespace sysctl tables resolve data pointers (from the previous kmemdup table to runtime pointer resolution via ctx), and that it is clearly worth fuzzing. I can check the EnableConfigs to ensure this is a valid approach. Given the potential for vulnerabilities, this definitely warrants aggressive fuzzing. I'm going to set up fuzzing to target this code path immediately. Let's verify our configuration of `PROC_SYSCTL`.
20/2	2026/09/26 19:13	tool	grepper	0m Error: no matches Args: { "Expression": "config PROC_SYSCTL" } Results: { "error": "no matches" }
21/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 22368 output: 25 thoughts: 11 Thoughts: Okay, here's my attempt at summarizing that thought process, tailored for an expert audience, and written in the first person: Investigating the Kernel Configuration for the Procfs Filesystem Alright, time to dig into the kernel's configuration options related to `/proc`. My immediate instinct is to check the `Kconfig` file within the `fs/proc` directory. I know that's where the majority of the configuration decisions for the proc filesystem are defined. I expect to find the settings that control which features are compiled in, which are modules, and potentially even some of the default behaviors. This is the place to start peeling back the layers on how the kernel builds the `/proc` filesystem and its functionality. Let's see what's in there.
22/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "SYSCTL", "PathPrefix": "fs/proc" } Results: { "Output": "fs/proc/Kconfig=67=config PROC_VMCORE_DEVICE_RAM\n--\nfs/proc/Kconfig-82-\nfs/proc/Kconfig:83:config SYSCTL\nfs/proc/Kconfig-84-\tbool \"Sysctl support (/proc/sys)\" if EXPERT\n--\nfs/proc/Makefile=31=proc-y\t+= thread_self.o\nfs/proc/Makefile:32:proc-$(CONFIG_SYSCTL)\t\t+= proc_sysctl.o\nfs/proc/Makefile-33-proc-$(CONFIG_NET)\t\t+= proc_net.o\n--\nfs/proc/internal.h=349=extern void proc_thread_self_init(void);\n--\nfs/proc/internal.h-353- /\nfs/proc/internal.h:354:#ifdef CONFIG_SYSCTL\nfs/proc/internal.h-355-extern int proc_sys_init(void);\n--\nfs/proc/proc_sysctl.c=53=EXPORT_SYMBOL(register_sysctl_mount_point);\n--\nfs/proc/proc_sysctl.c-55-#define sysctl_is_perm_empty_ctl_header(hptr)\t\t\\\nfs/proc/proc_sysctl.c:56:\t(hptr-\u003etype == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)\nfs/proc/proc_sysctl.c-57-#define sysctl_set_perm_empty_ctl_header(hptr)\t\t\\\nfs/proc/proc_sysctl.c:58:\t(hptr-\u003etype = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)\nfs/proc/proc_sysctl.c-59-#define sysctl_clear_perm_empty_ctl_header(hptr)\t\\\nfs/proc/proc_sysctl.c:60:\t(hptr-\u003etype = SYSCTL_TABLE_TYPE_DEFAULT)\nfs/proc/proc_sysctl.c-61-\n--\nfs/proc/proc_sysctl.c=571=static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter *iter,\n--\nfs/proc/proc_sysctl.c-614-\nfs/proc/proc_sysctl.c:615:\terror = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, \u0026kbuf, \u0026count,\nfs/proc/proc_sysctl.c-616-\t\t\t\t\t \u0026iocb-\u003eki_pos);\n" }
23/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23193 output: 33 thoughts: 31 Thoughts: Okay, here's my interpretation of that thought process, from an expert's perspective: Diving into the Kernel Configuration for Sysctl Right, `fs/proc/Kconfig` is the place to start when I'm looking at how the sysctl interface is configured within the kernel. My initial thought is that `config SYSCTL` will be defined there. I'm going to quickly check around line 83 – that's a pretty standard place to find related settings in Kconfig files. I'm expecting to find the relevant Kconfig fragment, related dependencies, and maybe some associated documentation for the `proc` filesystem's sysctl implementation. Hopefully, the surrounding lines will shed light on any specific build-time considerations or conditional dependencies related to the sysctl feature.
24/2	2026/09/26 19:13	tool	read-file	0m Args: { "File": "fs/proc/Kconfig", "FirstLine": 80, "LineCount": 25 } Results: { "Contents": " 80:\t\n 81:\t\t Relevant architectures should select NEED_PROC_VMCORE_DEVICE_RAM.\n 82:\t\n 83:\tconfig SYSCTL\n 84:\t\tbool \"Sysctl support (/proc/sys)\" if EXPERT\n 85:\t\tdepends on PROC_FS\n 86:\t\tdefault y\n 87:\t\thelp\n 88:\t\t The sysctl interface provides a means of dynamically changing\n 89:\t\t certain kernel parameters and variables on the fly without requiring\n 90:\t\t a recompile of the kernel or reboot of the system. The primary\n 91:\t\t interface is through /proc/sys. If you say Y here a tree of\n 92:\t\t modifiable sysctl entries will be generated beneath the\n 93:\t\t /proc/sys directory. They are explained in the files\n 94:\t\t in \u003cfile:Documentation/admin-guide/sysctl/\u003e. Note that enabling this\n 95:\t\t option will enlarge the kernel by at least 8 KB.\n 96:\t\n 97:\t\t As it is generally a good thing, you should say Y here unless\n 98:\t\t building a kernel for install/rescue disks or your system is very\n 99:\t\t limited in memory.\n 100:\t\n 101:\tconfig PROC_PAGE_MONITOR\n 102:\t \tdefault y\n 103:\t\tdepends on PROC_FS \u0026\u0026 MMU\n 104:\t\tbool \"Enable /proc page monitoring\" if EXPERT\n" }
25/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23807 output: 26 thoughts: 98 Thoughts: Okay, here's my breakdown of this. Dependencies and Configurations - A Quick Analysis Alright, let's see, it looks like we have a few modules here with some clear dependencies. I see that `SYSCTL` relies on `PROC_FS` – that's expected; `procfs` is a common source for control parameters. Then, `SYSVIPC_SYSCTL` builds on top of both `SYSVIPC` and `SYSCTL`, making it clear that IPC settings will likely be intertwined with system-wide controls. `POSIX_MQUEUE_SYSCTL` similarly hangs off `POSIX_MQUEUE` and `SYSCTL`, which makes sense. The interesting piece here is `create_ipc_ns` being tied to `CONFIG_IPC_NS`. That's the key. Since `IPC_NS` is the common thread, I'll need to check the Kconfig file for `init/Kconfig` to determine its configuration options. I need to understand what `CONFIG_IPC_NS` is actually doing in terms of enabling or disabling IPC namespace functionality.
26/2	2026/09/26 19:13	tool	grepper	0m Args: { "Expression": "config IPC_NS", "PathPrefix": "init/" } Results: { "Output": "init/Kconfig=1435=config TIME_NS_VDSO\n--\ninit/Kconfig-1437-\ninit/Kconfig:1438:config IPC_NS\ninit/Kconfig-1439-\tbool \"IPC namespace\"\n" }
27/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 24238 output: 33 thoughts: 17 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience and presented in the first person: Navigating the Kconfig Labyrinth Alright, time to dive into this. Let's get down to brass tacks. I need to take a look at the `init/Kconfig` file. Specifically, I'm thinking around line 1438. That usually gives a good starting point to investigate whatever dependency or configuration issue is currently at play. That specific area has often been a key node for handling initialization settings, and it’s usually where I find the answers to these kinds of build problems. I need to trace this specific area, look for any unusual configurations, and consider the implications of whatever the code around that line is doing. I can then use that information to refine my understanding of the issue and pinpoint the root cause. This seems like a reasonable place to begin.
28/2	2026/09/26 19:13	tool	read-file	0m Args: { "File": "init/Kconfig", "FirstLine": 1435, "LineCount": 20 } Results: { "Contents": "1435:\tconfig TIME_NS_VDSO\n1436:\t\tdef_bool TIME_NS \u0026\u0026 GENERIC_GETTIMEOFDAY\n1437:\t\n1438:\tconfig IPC_NS\n1439:\t\tbool \"IPC namespace\"\n1440:\t\tdepends on (SYSVIPC \|\| POSIX_MQUEUE)\n1441:\t\tdefault y\n1442:\t\thelp\n1443:\t\t In this namespace tasks work with IPC ids which correspond to\n1444:\t\t different IPC objects in different namespaces.\n1445:\t\n1446:\tconfig USER_NS\n1447:\t\tbool \"User namespace\"\n1448:\t\tdefault n\n1449:\t\thelp\n1450:\t\t This allows containers, i.e. vservers, to use user namespaces\n1451:\t\t to provide different user info for different servers.\n1452:\t\n1453:\t\t When user namespaces are enabled in the kernel it is\n1454:\t\t recommended that the MEMCG option also be enabled and that\n" }
29/2	2026/09/26 19:13	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 24758 output: 29 thoughts: 1202 Thoughts: Focus Symbol Selection for Kernel Fuzzing Okay, so I need to pick the right focus symbols for this fuzzing effort, given these kernel configuration options: `CONFIG_PROC_FS`, `CONFIG_SYSCTL`, `CONFIG_SYSVIPC`, `CONFIG_POSIX_MQUEUE`, and `CONFIG_IPC_NS`. The goal is to maximize fuzzing effectiveness by targeting specific feature logic and entry points, while avoiding ubiquitous functions that would dilute the fuzzing signal. I should also be mindful of the compiler's inlining behavior with static inline functions. Based on the commit's changes, here's what I'm thinking: First, let's look at the modified functions: I've got `__register_sysctl_table_ctx` in `fs/proc/proc_sysctl.c`. That looks like a direct API entrypoint for registering sysctl tables and should be a good candidate. Then there's `sysctl_apply_ctx`, a static function in the same file. I need to be careful with statics; the compiler might inline it. To be safe, I'll include its callers, `proc_sys_call_handler` and `proc_sys_permission` instead. They are still feature-specific but are not so generic. Now, let's consider `proc_sys_call_handler`. This function handles read/write operations for `/proc/sys` entries. Is that too broad? No, it only gets invoked for specific operations within the `/proc/sys/` space, so it seems targeted enough. `proc_sys_permission` is also related to `/proc/sys`, and is called for inodes in that path, so it seems specific enough as well. Then, there is `sysctl_check_table` (also in `fs/proc/proc_sysctl.c`). The patch significantly alters this function's validation logic, particularly regarding context data and table flags. This is definitely* relevant, and I should include it. I'll need to check if it's static or not; if so, I need to include the caller. Next, I need to consider `setup_ipc_sysctls` and `setup_mq_sysctls` (in `ipc/ipc_sysctl.c` and `ipc/mq_sysctl.c`, respectively). These functions seem like clear registration entrypoints for IPC and message queue sysctls, which aligns with the goal. The corresponding `retire_ipc_sysctls` and `retire_mq_sysctls` functions, however, are teardown callbacks. They are called during `free_ipc_ns`, which is automatic when an IPC namespace is unshared and the process exits. This is not the target of the fuzz. Looking back, `sysctl_apply_ctx` is static and potentially inlined. Given that `proc_sys_call_handler` and `proc_sys_permission` are the callers, I'm confident those should be on the list. So, here's my list of Focus Symbols, as a start: * `__register_sysctl_table_ctx` * `proc_sys_call_handler` * `proc_sys_permission` * `sysctl_check_table` * `setup_ipc_sysctls` * `setup_mq_sysctls` I'll keep an eye on how these perform, and I might need to refine this list based on fuzzing results.
30/2	2026/09/26 19:14	tool	grepper	0m Args: { "Expression": "sysctl_check_table", "PathPrefix": "fs/proc" } Results: { "Output": "fs/proc/proc_sysctl.c=1115=static int sysctl_err(const char path, const struct ctl_table table, char fmt, ...)\n--\nfs/proc/proc_sysctl.c-1130-\nfs/proc/proc_sysctl.c:1131:static int sysctl_check_table_array(const char path, const struct ctl_table table)\nfs/proc/proc_sysctl.c-1132-{\n--\nfs/proc/proc_sysctl.c-1167-\nfs/proc/proc_sysctl.c:1168:static int sysctl_check_table(const char path, struct ctl_table_header header)\nfs/proc/proc_sysctl.c-1169-{\n--\nfs/proc/proc_sysctl.c-1199-\t\t\telse\nfs/proc/proc_sysctl.c:1200:\t\t\t\terr \|= sysctl_check_table_array(path, entry);\nfs/proc/proc_sysctl.c-1201-\t\t}\n--\nfs/proc/proc_sysctl.c=1412=struct ctl_table_header __register_sysctl_table_ctx(\n--\nfs/proc/proc_sysctl.c-1430-\t\theader-\u003ectx = *ctx;\nfs/proc/proc_sysctl.c:1431:\tif (sysctl_check_table(path, header))\nfs/proc/proc_sysctl.c-1432-\t\tgoto fail;\n" }
31/2	2026/09/26 19:14	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27155 output: 263 thoughts: 841 Thoughts: Fuzzing Verdict: Confirmed Okay, let's break this down. First, `sysctl_check_table` is a static function called only by `__register_sysctl_table_ctx`. It's a fairly complex function, with loops and calls to things like `sysctl_err`, `sysctl_check_table_array`, so inlining is unlikely. But even if it were, `__register_sysctl_table_ctx` is non-static and its direct caller. This makes it a relevant entry point. So, the key functions that are in play here are: `__register_sysctl_table_ctx`, `sysctl_check_table`, `sysctl_apply_ctx`, `proc_sys_call_handler`, `proc_sys_permission`, `setup_ipc_sysctls`, and `setup_mq_sysctls`. I've taken a look at the diff and re-confirmed all the functions involved: `retire_ipc_sysctls` and `retire_mq_sysctls` are also present. And I am confident they are all specific to the Sysctl IPC/MQ feature and not core, ubiquitous kernel functions. That's good from a fuzzing perspective, as it narrows down the scope. Next, I need to verify the configuration requirements. The `EnableConfigs` list includes `PROC_FS`, `SYSCTL`, `SYSVIPC`, `POSIX_MQUEUE`, and `IPC_NS`. Now, let's verify if `SYSVIPC_SYSCTL` and `POSIX_MQUEUE_SYSCTL` are user-visible config options or are just selected/defaulted. Looking at `init/Kconfig`, I see that `SYSVIPC_SYSCTL` depends on `SYSVIPC` and `SYSCTL`, and is defaulted to `y`. It isn't a directly user-configurable option. However, that means we should include both SYSVIPC and SYSCTL. The same is true for `POSIX_MQUEUE_SYSCTL`. We can include these in `EnableConfigs`. Finally, let's confirm the requirements. The change modifies reachable code that is worth fuzzing, so "WorthFuzzing: True" is accurate. The focus symbols are specific and non-ubiquitous: `__register_sysctl_table_ctx`, `sysctl_apply_ctx`, `proc_sys_call_handler`, `proc_sys_permission`, `sysctl_check_table`, `setup_ipc_sysctls`, and `setup_mq_sysctls`. The configs also look correct: `SYSCTL`, `PROC_FS`, `SYSVIPC`, `POSIX_MQUEUE`, `IPC_NS`. Everything seems correct and I can confirm that this is a valid candidate for fuzzing.
32/2	2026/09/26 19:14	tool	set-results	0m Args: { "EnableConfigs": [ "SYSCTL", "PROC_FS", "SYSVIPC", "POSIX_MQUEUE", "IPC_NS" ], "FocusSymbols": [ "__register_sysctl_table_ctx", "sysctl_apply_ctx", "proc_sys_call_handler", "proc_sys_permission", "sysctl_check_table", "setup_ipc_sysctls", "setup_mq_sysctls" ], "Reasoning": "The patch introduces a new context-based data pointer resolution mechanism for sysctl entries (CTL_TABLE_F_CTX_DATA) to avoid duplicating ctl_tables when instantiating new IPC namespaces. This alters pointer calculation in core sysctl access paths (proc_sys_call_handler, proc_sys_permission) and adds new table validation checks in sysctl_check_table and __register_sysctl_table_ctx. This code is fully reachable via standard unshare(CLONE_NEWIPC) and /proc/sys read/write operations, making it valuable to fuzz for potential out-of-bounds pointer calculation issues or registration inconsistencies.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "SYSCTL", "PROC_FS", "SYSVIPC", "POSIX_MQUEUE", "IPC_NS" ], "FocusSymbols": [ "__register_sysctl_table_ctx", "sysctl_apply_ctx", "proc_sys_call_handler", "proc_sys_permission", "sysctl_check_table", "setup_ipc_sysctls", "setup_mq_sysctls" ], "Reasoning": "The patch introduces a new context-based data pointer resolution mechanism for sysctl entries (CTL_TABLE_F_CTX_DATA) to avoid duplicating ctl_tables when instantiating new IPC namespaces. This alters pointer calculation in core sysctl access paths (proc_sys_call_handler, proc_sys_permission) and adds new table validation checks in sysctl_check_table and __register_sysctl_table_ctx. This code is fully reachable via standard unshare(CLONE_NEWIPC) and /proc/sys read/write operations, making it valuable to fuzz for potential out-of-bounds pointer calculation issues or registration inconsistencies.", "WorthFuzzing": true }
33/1	2026/09/26 19:14	action	If	2m Args: { "WorthFuzzing": true } Results: null
34/2	2026/09/26 19:14	agent	kmsan-evaluator	2m Model: core Args: null Results: { "KMSANReasoning": "The patch refactors per-namespace sysctl tables in IPC and POSIX message queues (mq) to eliminate dynamic kmemdup allocations. Instead, it introduces `struct sysctl_context` and a flag `CTL_TABLE_F_CTX_DATA` to resolve per-namespace struct member offsets dynamically via `sysctl_apply_ctx()` into a local stack buffer (`ctx_entry`).\n\nKMSAN vs KASAN applicability analysis:\n1. Uninitialized memory reads / branching:\n - The stack variables `struct ctl_table ctx_entry` in `proc_sys_call_handler()` and `proc_sys_permission()` are passed as out-parameters to `sysctl_apply_ctx()`. When `CTL_TABLE_F_CTX_DATA` is set, `buf = entry;` fully initializes the struct from the static const sysctl table before updating `buf-\u003edata` and returning `buf`. When the flag is not set, `sysctl_apply_ctx()` returns `entry` directly, leaving `buf` untouched and completely unreferenced.\n - The `struct sysctl_context` created by `SYSCTL_CTX` initializes all struct fields (`inst` and `tmpl`) via a compound literal.\n - `struct ctl_table_header` is allocated using `kzalloc()`, and `struct ipc_namespace` is allocated using `kzalloc_obj()`.\n2. Kernel-to-userspace info-leaks:\n - `struct ctl_table` is an internal kernel structure and is never copied to user space. Data written to userspace by sysctl read handlers is formatted into `kbuf` allocated with `kvzalloc()`.\n3. Memory safety risks:\n - Any potential offset calculation errors (`(char )head-\u003ectx.inst + off`) would lead to out-of-bounds pointer dereferences, which are detected by KASAN, not KMSAN.\n\nTherefore, the patch does not expose any uninitialized memory risks or info-leaks. A dedicated KMSAN fuzzing session is not warranted; standard KASAN fuzzing is sufficient.", "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 72956c04a50c26de34979e555c595f8609103b90 Author: syz-cluster <triage@syzkaller.com> Date: Sat Sep 26 19:12:52 2026 +0000 syz-cluster: applied patch under review diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index 04a382178c657..1ed9f4e1a17e2 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -550,12 +550,31 @@ static struct dentry proc_sys_lookup(struct inode dir, struct dentry dentry, return err; } +/ Returns @entry itself when it is not flagged, else a resolved copy in @buf. / +static const struct ctl_table sysctl_apply_ctx(struct ctl_table_header head, + const struct ctl_table entry, + struct ctl_table buf) +{ + ptrdiff_t off; + + if (!(entry->flags & CTL_TABLE_F_CTX_DATA)) + return entry; + + off = (const char )entry->data - (const char )head->ctx.tmpl; + + buf = entry; + buf->data = (char )head->ctx.inst + off; + + return buf; +} + static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter, int write) { struct inode inode = file_inode(iocb->ki_filp); struct ctl_table_header head = grab_header(inode); const struct ctl_table table = PROC_I(inode)->sysctl_entry; + struct ctl_table ctx_entry; size_t count = iov_iter_count(iter); char kbuf; ssize_t error; @@ -567,6 +586,8 @@ static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter, * At this point we know that the sysctl was not unregistered * and won't be until we finish. / + table = sysctl_apply_ctx(head, table, &ctx_entry); + error = -EPERM; if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ)) goto out; @@ -797,6 +818,7 @@ static int proc_sys_permission(struct mnt_idmap idmap, / struct ctl_table_header head; const struct ctl_table table; + struct ctl_table ctx_entry; int error; / Executable files are not allowed under /proc/sys/ / @@ -810,8 +832,11 @@ static int proc_sys_permission(struct mnt_idmap idmap, table = PROC_I(inode)->sysctl_entry; if (!table) /* global root - r-xr-xr-x / error = mask & MAY_WRITE ? -EACCES : 0; - else / Use the permissions on the sysctl table entry / + else { + / ->permissions may inspect the entry, so resolve it first. / + table = sysctl_apply_ctx(head, table, &ctx_entry); error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK); + } sysctl_head_finish(head); return error; @@ -1143,10 +1168,18 @@ static int sysctl_check_table_array(const char path, const struct ctl_table ta static int sysctl_check_table(const char path, struct ctl_table_header header) { const struct ctl_table entry; + u8 flagged = 0; int err = 0; list_for_each_table_entry(entry, header) { if (!entry->procname) err \|= sysctl_err(path, entry, "procname is null"); + if (entry->flags & CTL_TABLE_F_CTX_DATA) { + if (!entry->data) + err \|= sysctl_err(path, entry, "No data to resolve"); + if (!header->ctx.inst \|\| !header->ctx.tmpl) + err \|= sysctl_err(path, entry, "No context to resolve against"); + } + flagged \|= entry->flags & CTL_TABLE_F_CTX; if ((entry->proc_handler == proc_dostring) \|\| (entry->proc_handler == proc_dobool) \|\| (entry->proc_handler == proc_dointvec) \|\| @@ -1173,6 +1206,12 @@ static int sysctl_check_table(const char path, struct ctl_table_header header) err \|= sysctl_err(path, entry, "bogus .mode 0%o", entry->mode); } + /* A context nobody resolves against is a forgotten flag. / + if (!flagged && (header->ctx.inst \|\| header->ctx.tmpl)) { + pr_err("sysctl table check failed: %s context given but no entry is flagged\n", + path); + err = -EINVAL; + } return err; } @@ -1324,7 +1363,7 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) } /** - * __register_sysctl_table - register a leaf sysctl table + * __register_sysctl_table_ctx - register a leaf sysctl table * @set: Sysctl tree to register on * @path: The path to the directory the sysctl table is in. * @@ -1333,6 +1372,9 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) be a global or dynamically allocated by the caller and free'd later * after sysctl unregistration. * @table_size : The number of elements in table + * @ctx: instances that entries flagged CTL_TABLE_F_CTX_* resolve against, see + * struct sysctl_context. Copied, so it may be on stack. %NULL when no + * entry is flagged. * * Register a sysctl table hierarchy. @table should be a filled in ctl_table * array. @@ -1343,6 +1385,7 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) data - a pointer to data for use by proc_handler * maxlen - the maximum size in bytes of the data * mode - the file permissions for the /proc/sys file + * flags - CTL_TABLE_F_* bits naming members to resolve against @ctx * type - Defines the target type (described in struct definition) * proc_handler - the text handler routine (described below) * @@ -1366,9 +1409,10 @@ static struct ctl_dir sysctl_mkdir_p(struct ctl_dir dir, const char path) This routine returns %NULL on a failure to register, and a pointer * to the table header on success. / -struct ctl_table_header __register_sysctl_table( +struct ctl_table_header __register_sysctl_table_ctx( struct ctl_table_set set, - const char path, const struct ctl_table table, size_t table_size) + const char path, const struct ctl_table table, size_t table_size, + const struct sysctl_context ctx) { struct ctl_table_root root = set->dir.header.root; struct ctl_table_header header; @@ -1382,6 +1426,8 @@ struct ctl_table_header __register_sysctl_table( node = (struct ctl_node )(header + 1); init_header(header, root, set, node, table, table_size); + if (ctx) + header->ctx = ctx; if (sysctl_check_table(path, header)) goto fail; @@ -1427,7 +1473,7 @@ struct ctl_table_header __register_sysctl_table( Register a sysctl table. @table should be a filled in ctl_table * array. A completely 0 filled entry terminates the table. * - * See __register_sysctl_table for more details. + * See __register_sysctl_table_ctx for more details. / struct ctl_table_header register_sysctl_sz(const char path, const struct ctl_table table, size_t table_size) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index e5d7226ab6f5a..b2c57c530bdc9 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -22,6 +22,8 @@ #ifndef _LINUX_SYSCTL_H #define _LINUX_SYSCTL_H +#include <linux/bits.h> +#include <linux/build_bug.h> #include <linux/list.h> #include <linux/rcupdate.h> #include <linux/wait.h> @@ -224,12 +226,50 @@ struct ctl_table { void data; int maxlen; umode_t mode; + u8 flags; / CTL_TABLE_F_* / proc_handler proc_handler; /* Callback for text formatting / struct ctl_table_poll poll; void extra1; void extra2; } __randomize_layout; +/* + * ctl_table::flags. Resolve the corresponding member against the + * registration context instead of using it as it stands. + / +#define CTL_TABLE_F_CTX_DATA BIT(0) +#define CTL_TABLE_F_CTX CTL_TABLE_F_CTX_DATA + +/* + * struct sysctl_context - ctl_table specific context + * @inst: entry location + * @tmpl: struct template (used to calculate offset into @inst) + * + * @inst/@tmpl pair is used to overlay the ctl_table entry before calling + * proc_handler. This is relevant when struct members (like ->data) are + * somewhere different than the const static ctl_table array (think + * namespaces). Build it with SYSCTL_CTX() so the compiler checks that + * both point at the same type. + / +struct sysctl_context { + void inst; + const void tmpl; +}; + +/* + * SYSCTL_CTX - build a struct sysctl_context + * @_inst: the instance this registration describes + * @_tmpl: the instance the table's data members name + * + * Fails to build unless @_inst and @_tmpl point at the same type. + / +#define SYSCTL_CTX(_inst, _tmpl) \ + ((struct sysctl_context){ \ + .inst = (_inst) + \ + BUILD_BUG_ON_ZERO(!__same_type((_inst), (_tmpl))), \ + .tmpl = (_tmpl), \ + }) + struct ctl_node { struct rb_node node; struct ctl_table_header header; @@ -244,6 +284,7 @@ struct ctl_node { * something is removed from inodes * @nreg: When nreg drops to 0 the ctl_table_header will be unregistered. * @rcu: Delays the freeing of the inode. Introduced with "unfuck proc_sysctl ->d_compare()" + * @ctx: instances given to __register_sysctl_table_ctx(), see struct sysctl_context * * @type: Enumeration to differentiate between ctl target types: * type.SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations @@ -268,6 +309,7 @@ struct ctl_table_header { struct ctl_dir parent; struct ctl_node node; struct hlist_head inodes; /* head for proc_inode->sysctl_inodes / + struct sysctl_context ctx; enum { SYSCTL_TABLE_TYPE_DEFAULT, SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY, @@ -305,9 +347,18 @@ extern void setup_sysctl_set(struct ctl_table_set p, int (is_seen)(struct ctl_table_set )); extern void retire_sysctl_set(struct ctl_table_set set); -struct ctl_table_header __register_sysctl_table( +struct ctl_table_header __register_sysctl_table_ctx( + struct ctl_table_set set, + const char path, const struct ctl_table table, size_t table_size, + const struct sysctl_context ctx); + +static inline struct ctl_table_header __register_sysctl_table( struct ctl_table_set set, - const char path, const struct ctl_table table, size_t table_size); + const char path, const struct ctl_table table, size_t table_size) +{ + return __register_sysctl_table_ctx(set, path, table, table_size, NULL); +} + struct ctl_table_header register_sysctl_sz(const char path, const struct ctl_table table, size_t table_size); void unregister_sysctl_table(struct ctl_table_header * table); diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c index d038d944257f6..5d73487bb81c0 100644 --- a/ipc/ipc_sysctl.c +++ b/ipc/ipc_sysctl.c @@ -13,7 +13,6 @@ #include <linux/capability.h> #include <linux/ipc_namespace.h> #include <linux/msg.h> -#include <linux/slab.h> #include <linux/cred.h> #include "util.h" @@ -79,6 +78,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_ctlmax, .maxlen = sizeof(init_ipc_ns.shm_ctlmax), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_doulongvec_minmax, }, { @@ -86,6 +86,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_ctlall, .maxlen = sizeof(init_ipc_ns.shm_ctlall), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_doulongvec_minmax, }, { @@ -93,6 +94,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_ctlmni, .maxlen = sizeof(init_ipc_ns.shm_ctlmni), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = &ipc_mni, @@ -102,6 +104,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.shm_rmid_forced, .maxlen = sizeof(init_ipc_ns.shm_rmid_forced), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_ipc_dointvec_minmax_orphans, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, @@ -111,6 +114,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.msg_ctlmax, .maxlen = sizeof(init_ipc_ns.msg_ctlmax), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -120,6 +124,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.msg_ctlmni, .maxlen = sizeof(init_ipc_ns.msg_ctlmni), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = &ipc_mni, @@ -138,6 +143,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.msg_ctlmnb, .maxlen = sizeof(init_ipc_ns.msg_ctlmnb), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -147,6 +153,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.sem_ctls, .maxlen = 4sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_ipc_sem_dointvec, }, #ifdef CONFIG_CHECKPOINT_RESTORE @@ -155,6 +162,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.ids[IPC_SEM_IDS].next_id, .maxlen = sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id), .mode = 0444, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -164,6 +172,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.ids[IPC_MSG_IDS].next_id, .maxlen = sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id), .mode = 0444, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -173,6 +182,7 @@ static const struct ctl_table ipc_sysctls[] = { .data = &init_ipc_ns.ids[IPC_SHM_IDS].next_id, .maxlen = sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id), .mode = 0444, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_INT_MAX, @@ -244,57 +254,15 @@ static struct ctl_table_root set_root = { bool setup_ipc_sysctls(struct ipc_namespace ns) { - struct ctl_table tbl; + struct sysctl_context ctx = SYSCTL_CTX(ns, &init_ipc_ns); setup_sysctl_set(&ns->ipc_set, &set_root, set_is_seen); - tbl = kmemdup(ipc_sysctls, sizeof(ipc_sysctls), GFP_KERNEL); - if (tbl) { - int i; - - for (i = 0; i < ARRAY_SIZE(ipc_sysctls); i++) { - if (tbl[i].data == &init_ipc_ns.shm_ctlmax) - tbl[i].data = &ns->shm_ctlmax; - - else if (tbl[i].data == &init_ipc_ns.shm_ctlall) - tbl[i].data = &ns->shm_ctlall; - - else if (tbl[i].data == &init_ipc_ns.shm_ctlmni) - tbl[i].data = &ns->shm_ctlmni; - - else if (tbl[i].data == &init_ipc_ns.shm_rmid_forced) - tbl[i].data = &ns->shm_rmid_forced; - - else if (tbl[i].data == &init_ipc_ns.msg_ctlmax) - tbl[i].data = &ns->msg_ctlmax; - - else if (tbl[i].data == &init_ipc_ns.msg_ctlmni) - tbl[i].data = &ns->msg_ctlmni; - - else if (tbl[i].data == &init_ipc_ns.msg_ctlmnb) - tbl[i].data = &ns->msg_ctlmnb; - - else if (tbl[i].data == &init_ipc_ns.sem_ctls) - tbl[i].data = &ns->sem_ctls; -#ifdef CONFIG_CHECKPOINT_RESTORE - else if (tbl[i].data == &init_ipc_ns.ids[IPC_SEM_IDS].next_id) - tbl[i].data = &ns->ids[IPC_SEM_IDS].next_id; - - else if (tbl[i].data == &init_ipc_ns.ids[IPC_MSG_IDS].next_id) - tbl[i].data = &ns->ids[IPC_MSG_IDS].next_id; - - else if (tbl[i].data == &init_ipc_ns.ids[IPC_SHM_IDS].next_id) - tbl[i].data = &ns->ids[IPC_SHM_IDS].next_id; -#endif - else - tbl[i].data = NULL; - } - - ns->ipc_sysctls = __register_sysctl_table(&ns->ipc_set, "kernel", tbl, - ARRAY_SIZE(ipc_sysctls)); - } + ns->ipc_sysctls = __register_sysctl_table_ctx(&ns->ipc_set, "kernel", + ipc_sysctls, + ARRAY_SIZE(ipc_sysctls), + &ctx); if (!ns->ipc_sysctls) { - kfree(tbl); retire_sysctl_set(&ns->ipc_set); return false; } @@ -304,12 +272,8 @@ bool setup_ipc_sysctls(struct ipc_namespace ns) void retire_ipc_sysctls(struct ipc_namespace ns) { - const struct ctl_table tbl; - - tbl = ns->ipc_sysctls->ctl_table_arg; unregister_sysctl_table(ns->ipc_sysctls); retire_sysctl_set(&ns->ipc_set); - kfree(tbl); } static int __init ipc_sysctl_init(void) diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c index 0dd12e1c9f53e..9919e2d3a11a4 100644 --- a/ipc/mq_sysctl.c +++ b/ipc/mq_sysctl.c @@ -11,7 +11,6 @@ #include <linux/stat.h> #include <linux/capability.h> -#include <linux/slab.h> #include <linux/cred.h> static int msg_max_limit_min = MIN_MSGMAX; @@ -26,6 +25,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_queues_max, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec, }, { @@ -33,6 +33,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msg_max, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_max_limit_min, .extra2 = &msg_max_limit_max, @@ -42,6 +43,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msgsize_max, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_maxsize_limit_min, .extra2 = &msg_maxsize_limit_max, @@ -51,6 +53,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msg_default, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_max_limit_min, .extra2 = &msg_max_limit_max, @@ -60,6 +63,7 @@ static const struct ctl_table mq_sysctls[] = { .data = &init_ipc_ns.mq_msgsize_default, .maxlen = sizeof(int), .mode = 0644, + .flags = CTL_TABLE_F_CTX_DATA, .proc_handler = proc_dointvec_minmax, .extra1 = &msg_maxsize_limit_min, .extra2 = &msg_maxsize_limit_max, @@ -116,39 +120,15 @@ static struct ctl_table_root set_root = { bool setup_mq_sysctls(struct ipc_namespace ns) { - struct ctl_table tbl; + struct sysctl_context ctx = SYSCTL_CTX(ns, &init_ipc_ns); setup_sysctl_set(&ns->mq_set, &set_root, set_is_seen); - tbl = kmemdup(mq_sysctls, sizeof(mq_sysctls), GFP_KERNEL); - if (tbl) { - int i; - - for (i = 0; i < ARRAY_SIZE(mq_sysctls); i++) { - if (tbl[i].data == &init_ipc_ns.mq_queues_max) - tbl[i].data = &ns->mq_queues_max; - - else if (tbl[i].data == &init_ipc_ns.mq_msg_max) - tbl[i].data = &ns->mq_msg_max; - - else if (tbl[i].data == &init_ipc_ns.mq_msgsize_max) - tbl[i].data = &ns->mq_msgsize_max; - - else if (tbl[i].data == &init_ipc_ns.mq_msg_default) - tbl[i].data = &ns->mq_msg_default; - - else if (tbl[i].data == &init_ipc_ns.mq_msgsize_default) - tbl[i].data = &ns->mq_msgsize_default; - else - tbl[i].data = NULL; - } - - ns->mq_sysctls = __register_sysctl_table(&ns->mq_set, - "fs/mqueue", tbl, - ARRAY_SIZE(mq_sysctls)); - } + ns->mq_sysctls = __register_sysctl_table_ctx(&ns->mq_set, "fs/mqueue", + mq_sysctls, + ARRAY_SIZE(mq_sysctls), + &ctx); if (!ns->mq_sysctls) { - kfree(tbl); retire_sysctl_set(&ns->mq_set); return false; } @@ -158,10 +138,6 @@ bool setup_mq_sysctls(struct ipc_namespace ns) void retire_mq_sysctls(struct ipc_namespace ns) { - const struct ctl_table *tbl; - - tbl = ns->mq_sysctls->ctl_table_arg; unregister_sysctl_table(ns->mq_sysctls); retire_sysctl_set(&ns->mq_set); - kfree(tbl); }
35/3	2026/09/26 19:14	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 9849 output: 37 thoughts: 908 Thoughts: KMSAN Fuzzing Evaluation of sysctl Patch Okay, let's break this down. The user wants me to decide if this sysctl patch warrants a KMSAN fuzzing session. I need to understand the potential for memory safety issues. First, I see the patch touches `fs/proc/proc_sysctl.c`, `include/linux/sysctl.h`, `ipc/ipc_sysctl.c`, and `ipc/mq_sysctl.c`. That's a good starting point. It looks like it's addressing sysctl table handling, specifically for per-namespace instances. The old method of `kmemdup` and patching pointers sounds clunky, so this new `sysctl_context` structure with `inst`, `tmpl`, and the `CTL_TABLE_F_CTX_DATA` flag seems like a more elegant approach. Now, I need to understand `sysctl_apply_ctx`. It appears to conditionally return a modified copy of a `ctl_table` entry. The `CTL_TABLE_F_CTX_DATA` flag is key here. If the flag is not set, the original `entry` pointer is returned. If it is set, a new `ctl_table` (`buf`) is populated, with the data pointer adjusted to point to the namespace instance. My spidey sense is tingling now... Specifically because of `proc_sys_call_handler` and `proc_sys_permission`, where they declare the `ctx_entry` on the stack. My concern is around the potential for uninitialized memory usage. I see `struct ctl_table ctx_entry;` is allocated locally. Then `sysctl_apply_ctx` is called, and the return value is assigned to `table`. Okay, the crucial question is this: if `CTL_TABLE_F_CTX_DATA` isn't set, `table` will still point to the original `entry` which is fine, but `ctx_entry` will be untouched. So, `ctx_entry` isn't used. But if the flag is set, the code copies `entry` into `ctx_entry` then overwrites `data`. However, it performs a struct copy, so I need to know: Does `struct ctl_table` have any padding? If there is padding, does the copy in `buf = entry` initialize all of it? If not, there's a possible uninitialized memory read or write here, leading to KMSAN issues! The fact that the table, `ipc_sysctls[]` is in `.rodata` and zero-initialized is a relief, but still, I need to confirm `ctx_entry`'s use in those functions. Therefore, I need to see how `table` (which points either to `entry` or the modified `ctx_entry`) is subsequently used within `proc_sys_call_handler` and `proc_sys_permission`, and any other spots, to see if an uninitialized value is read or leaked. Let me go read the surrounding code in `fs/proc/proc_sysctl.c` around those functions.
36/3	2026/09/26 19:14	tool	grepper	0m Args: { "Expression": "proc_sys_call_handler", "PathPrefix": "fs/proc/proc_sysctl.c" } Results: { "Output": "fs/proc/proc_sysctl.c=554=static const struct ctl_table sysctl_apply_ctx(struct ctl_table_header head,\n--\nfs/proc/proc_sysctl.c-570-\nfs/proc/proc_sysctl.c:571:static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter,\nfs/proc/proc_sysctl.c-572-\t\tint write)\n--\nfs/proc/proc_sysctl.c=640=static ssize_t proc_sys_read(struct kiocb iocb, struct iov_iter iter)\nfs/proc/proc_sysctl.c-641-{\nfs/proc/proc_sysctl.c:642:\treturn proc_sys_call_handler(iocb, iter, 0);\nfs/proc/proc_sysctl.c-643-}\n--\nfs/proc/proc_sysctl.c=645=static ssize_t proc_sys_write(struct kiocb iocb, struct iov_iter iter)\nfs/proc/proc_sysctl.c-646-{\nfs/proc/proc_sysctl.c:647:\treturn proc_sys_call_handler(iocb, iter, 1);\nfs/proc/proc_sysctl.c-648-}\n" }
37/3	2026/09/26 19:14	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 11833 output: 38 thoughts: 27 Thoughts: Okay, here's my interpretation of what's going on, formatted as you requested: Delving into the Kernel's System Control Interface Alright, time to dive into the kernel's internals. I'm going to focus my attention on the `fs/proc/proc_sysctl.c` file, specifically lines 565 through 640. This chunk likely deals with the implementation of the proc filesystem's interface for system control variables – the mechanism by which user-space programs can read and modify kernel parameters on the fly. This is a crucial area; misconfigurations here can lead to anything from subtle performance degradation to outright system instability, so I want to get a solid grasp of this particular code segment. I'm expecting to find the details of how some of the sysctl entries are mapped to underlying kernel data structures. I am likely looking at the control logic and parameter checking too, and trying to identify any potential security implications or performance bottlenecks. I need to see how the kernel handles the reads and writes, and how it ensures data consistency. Let's see what gems are hidden in this section.
38/3	2026/09/26 19:14	tool	read-file	0m Args: { "File": "fs/proc/proc_sysctl.c", "FirstLine": 565, "LineCount": 80 } Results: { "Contents": " 565:\t\tbuf = entry;\n 566:\t\tbuf-\u003edata = (char )head-\u003ectx.inst + off;\n 567:\t\n 568:\t\treturn buf;\n 569:\t}\n 570:\t\n 571:\tstatic ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter,\n 572:\t\t\tint write)\n 573:\t{\n 574:\t\tstruct inode inode = file_inode(iocb-\u003eki_filp);\n 575:\t\tstruct ctl_table_header head = grab_header(inode);\n 576:\t\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\n 577:\t\tstruct ctl_table ctx_entry;\n 578:\t\tsize_t count = iov_iter_count(iter);\n 579:\t\tchar kbuf;\n 580:\t\tssize_t error;\n 581:\t\n 582:\t\tif (IS_ERR(head))\n 583:\t\t\treturn PTR_ERR(head);\n 584:\t\n 585:\t\t/\n 586:\t\t * At this point we know that the sysctl was not unregistered\n 587:\t\t * and won't be until we finish.\n 588:\t\t /\n 589:\t\ttable = sysctl_apply_ctx(head, table, \u0026ctx_entry);\n 590:\t\n 591:\t\terror = -EPERM;\n 592:\t\tif (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))\n 593:\t\t\tgoto out;\n 594:\t\n 595:\t\t/ if that can happen at all, it should be -EINVAL, not -EISDIR /\n 596:\t\terror = -EINVAL;\n 597:\t\tif (!table-\u003eproc_handler)\n 598:\t\t\tgoto out;\n 599:\t\n 600:\t\t/ don't even try if the size is too large /\n 601:\t\terror = -ENOMEM;\n 602:\t\tif (count \u003e= KMALLOC_MAX_SIZE)\n 603:\t\t\tgoto out;\n 604:\t\tkbuf = kvzalloc(count + 1, GFP_KERNEL);\n 605:\t\tif (!kbuf)\n 606:\t\t\tgoto out;\n 607:\t\n 608:\t\tif (write) {\n 609:\t\t\terror = -EFAULT;\n 610:\t\t\tif (!copy_from_iter_full(kbuf, count, iter))\n 611:\t\t\t\tgoto out_free_buf;\n 612:\t\t\tkbuf[count] = '\\0';\n 613:\t\t}\n 614:\t\n 615:\t\terror = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, \u0026kbuf, \u0026count,\n 616:\t\t\t\t\t\t \u0026iocb-\u003eki_pos);\n 617:\t\tif (error)\n 618:\t\t\tgoto out_free_buf;\n 619:\t\n 620:\t\t/ careful: calling conventions are nasty here /\n 621:\t\terror = table-\u003eproc_handler(table, write, kbuf, \u0026count, \u0026iocb-\u003eki_pos);\n 622:\t\tif (error)\n 623:\t\t\tgoto out_free_buf;\n 624:\t\n 625:\t\tif (!write) {\n 626:\t\t\terror = -EFAULT;\n 627:\t\t\tif (copy_to_iter(kbuf, count, iter) \u003c count)\n 628:\t\t\t\tgoto out_free_buf;\n 629:\t\t}\n 630:\t\n 631:\t\terror = count;\n 632:\tout_free_buf:\n 633:\t\tkvfree(kbuf);\n 634:\tout:\n 635:\t\tsysctl_head_finish(head);\n 636:\t\n 637:\t\treturn error;\n 638:\t}\n 639:\t\n 640:\tstatic ssize_t proc_sys_read(struct kiocb iocb, struct iov_iter *iter)\n 641:\t{\n 642:\t\treturn proc_sys_call_handler(iocb, iter, 0);\n 643:\t}\n 644:\t\n" }
39/3	2026/09/26 19:14	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 13289 output: 34 thoughts: 20 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: Digging Deeper into System Security Right, so we're talking about system-level permissions. We've got a handle on the broader context, the architectural overview, and maybe even a few specific vulnerabilities. Now, to truly understand the granular control, we need to drill down into some specific areas. My mind's immediately jumping to two key components: `proc_sys_permission` and `sysctl_perm`. These are the bedrock, aren’t they? They're where the rubber meets the road in terms of regulating access to critical system parameters and controlling how processes interact with the kernel. I need to understand how these elements function in relation to everything else we've discussed. Are there subtle differences in their enforcement? Interdependencies? Areas where misconfiguration creates potential attack vectors? Let's analyze.
40/3	2026/09/26 19:14	tool	grepper	0m Args: { "Expression": "sysctl_perm", "PathPrefix": "fs/proc/proc_sysctl.c" } Results: { "Output": "fs/proc/proc_sysctl.c=400=static void next_entry(struct ctl_table_header phead, const struct ctl_table pentry)\n--\nfs/proc/proc_sysctl.c-420-/\nfs/proc/proc_sysctl.c:421: sysctl_perm does NOT grant the superuser all rights automatically, because\nfs/proc/proc_sysctl.c-422- * some sysctl variables are readonly even to root.\n--\nfs/proc/proc_sysctl.c=425=static int test_perm(int mode, int op)\n--\nfs/proc/proc_sysctl.c-435-\nfs/proc/proc_sysctl.c:436:static int sysctl_perm(struct ctl_table_header head, const struct ctl_table table, int op)\nfs/proc/proc_sysctl.c-437-{\n--\nfs/proc/proc_sysctl.c=571=static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter,\n--\nfs/proc/proc_sysctl.c-591-\terror = -EPERM;\nfs/proc/proc_sysctl.c:592:\tif (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))\nfs/proc/proc_sysctl.c-593-\t\tgoto out;\n--\nfs/proc/proc_sysctl.c=812=static int proc_sys_permission(struct mnt_idmap *idmap,\n--\nfs/proc/proc_sysctl.c-837-\t\ttable = sysctl_apply_ctx(head, table, \u0026ctx_entry);\nfs/proc/proc_sysctl.c:838:\t\terror = sysctl_perm(head, table, mask \u0026 ~MAY_NOT_BLOCK);\nfs/proc/proc_sysctl.c-839-\t}\n" }
41/3	2026/09/26 19:14	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14040 output: 38 thoughts: 10 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and rendered in the first person: Analyzing `sysctl_perm` - A Quick Check Right, let's dive into this `sysctl_perm` variable. First instinct is a quick mental scan. I need to understand its role. What are we dealing with? Is it a permission setting related to a specific kernel parameter, or a broader system-wide access control mechanism managed through `sysctl`? The naming convention suggests it’s permission-related, probably controlling what a user or process can do with particular sysctl variables. My experience tells me there are several ways to implement this, so I need to assess the specific implementation. The nuances are key: is it a simple boolean, a mask, a user/group based access control, or something more complex? The architecture of this will dictate how to proceed with any vulnerability scanning, auditing, or hardening steps. Time to dig deeper into the code.
42/3	2026/09/26 19:14	tool	read-file	0m Args: { "File": "fs/proc/proc_sysctl.c", "FirstLine": 430, "LineCount": 40 } Results: { "Contents": " 430:\t\t\tmode \u003e\u003e= 3;\n 431:\t\tif ((op \u0026 ~mode \u0026 (MAY_READ\|MAY_WRITE\|MAY_EXEC)) == 0)\n 432:\t\t\treturn 0;\n 433:\t\treturn -EACCES;\n 434:\t}\n 435:\t\n 436:\tstatic int sysctl_perm(struct ctl_table_header head, const struct ctl_table table, int op)\n 437:\t{\n 438:\t\tstruct ctl_table_root root = head-\u003eroot;\n 439:\t\tint mode;\n 440:\t\n 441:\t\tif (root-\u003epermissions)\n 442:\t\t\tmode = root-\u003epermissions(head, table);\n 443:\t\telse\n 444:\t\t\tmode = table-\u003emode;\n 445:\t\n 446:\t\treturn test_perm(mode, op);\n 447:\t}\n 448:\t\n 449:\tstatic struct inode proc_sys_make_inode(struct super_block sb,\n 450:\t\t\tstruct ctl_table_header head, const struct ctl_table table)\n 451:\t{\n 452:\t\tstruct ctl_table_root root = head-\u003eroot;\n 453:\t\tstruct inode inode;\n 454:\t\tstruct proc_inode ei;\n 455:\t\n 456:\t\tinode = new_inode(sb);\n 457:\t\tif (!inode)\n 458:\t\t\treturn ERR_PTR(-ENOMEM);\n 459:\t\n 460:\t\tinode-\u003ei_ino = get_next_ino();\n 461:\t\n 462:\t\tei = PROC_I(inode);\n 463:\t\n 464:\t\tspin_lock(\u0026sysctl_lock);\n 465:\t\tif (unlikely(head-\u003eunregistering)) {\n 466:\t\t\tspin_unlock(\u0026sysctl_lock);\n 467:\t\t\tiput(inode);\n 468:\t\t\treturn ERR_PTR(-ENOENT);\n 469:\t\t}\n" }
43/3	2026/09/26 19:14	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14858 output: 19 thoughts: 40 Thoughts: Okay, let's dive into this `root->permissions` thing. I'm curious to see how this hypothetical implementation would actually behave. My first thought is: What's the impact of this particular member? How is it defined? I need to get a clear picture before I can even begin to think about the architectural implications or potential bugs. Investigating the "root->permissions" Implementation I'm immediately going to search the codebase. A quick `grep` for `\.permissions\s*=` should pinpoint any instances where that particular field is defined or assigned a value. I'm focusing on those instances for now. That should give me a good starting point to understand its structure. Knowing the definition is key; its data type, and its intended function within the system. Understanding this field is my focus right now, which is a starting point for thinking about this function.
44/3	2026/09/26 19:14	tool	grepper	0m Args: { "Expression": "\\.permissions\\s=" } Results:* { "Output": "drivers/infiniband/hw/efa/efa_com_cmd.c=225=int efa_com_register_mr(struct efa_com_dev edev,\n--\ndrivers/infiniband/hw/efa/efa_com_cmd.c-239-\tmr_cmd.iova = params-\u003eiova;\ndrivers/infiniband/hw/efa/efa_com_cmd.c:240:\tmr_cmd.permissions = params-\u003epermissions;\ndrivers/infiniband/hw/efa/efa_com_cmd.c-241-\n--\ndrivers/infiniband/hw/efa/efa_verbs.c=1665=static int efa_register_mr(struct ib_pd ibpd, struct efa_mr *mr, u64 start,\n--\ndrivers/infiniband/hw/efa/efa_verbs.c-1678-\tparams.mr_length_in_bytes = length;\ndrivers/infiniband/hw/efa/efa_verbs.c:1679:\tparams.permissions = access_flags;\ndrivers/infiniband/hw/efa/efa_verbs.c-1680-\n--\nipc/ipc_sysctl.c=249=static struct ctl_table_root set_root = {\nipc/ipc_sysctl.c-250-\t.lookup = set_lookup,\nipc/ipc_sysctl.c:251:\t.permissions = ipc_permissions,\nipc/ipc_sysctl.c-252-\t.set_ownership = ipc_set_ownership,\n--\nipc/mq_sysctl.c=115=static struct ctl_table_root set_root = {\nipc/mq_sysctl.c-116-\t.lookup = set_lookup,\nipc/mq_sysctl.c:117:\t.permissions = mq_permissions,\nipc/mq_sysctl.c-118-\t.set_ownership = mq_set_ownership,\n--\nkernel/pid.c=763=static struct ctl_table_root pid_table_root = {\nkernel/pid.c-764-\t.lookup\t\t= pid_table_root_lookup,\nkernel/pid.c:765:\t.permissions\t= pid_table_root_permissions,\nkernel/pid.c-766-\t.set_ownership\t= pid_table_root_set_ownership,\n--\nkernel/ucount.c=59=static struct ctl_table_root set_root = {\nkernel/ucount.c-60-\t.lookup = set_lookup,\nkernel/ucount.c:61:\t.permissions = set_permissions,\nkernel/ucount.c-62-};\n--\nnet/sysctl_net.c=72=static struct ctl_table_root net_sysctl_root = {\nnet/sysctl_net.c-73-\t.lookup = net_ctl_header_lookup,\nnet/sysctl_net.c:74:\t.permissions = net_ctl_permissions,\nnet/sysctl_net.c-75-\t.set_ownership = net_ctl_set_ownership,\n--\ntools/testing/selftests/sgx/main.c=720=TEST_F(enclave, tcs_permissions)\n--\ntools/testing/selftests/sgx/main.c-758-\tioc.length = PAGE_SIZE;\ntools/testing/selftests/sgx/main.c:759:\tioc.permissions = SGX_SECINFO_R;\ntools/testing/selftests/sgx/main.c-760-\n--\ntools/testing/selftests/sgx/main.c=778=TEST_F(enclave, epcm_permissions)\n--\ntools/testing/selftests/sgx/main.c-868-\trestrict_ioc.length = PAGE_SIZE;\ntools/testing/selftests/sgx/main.c:869:\trestrict_ioc.permissions = SGX_SECINFO_R;\ntools/testing/selftests/sgx/main.c-870-\n" }
45/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16128 output: 25 thoughts: 24 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Diving into IPC Permissions Alright, let's get down to brass tacks. I'm seeing `ipc_permissions` and `mq_permissions` thrown around – immediately, I'm thinking about shared memory, message queues, semaphores, the whole Inter-Process Communication (IPC) shebang. My first instinct is to zero in on `ipc_permissions`. I want to understand exactly what that variable is doing. Is it setting access control lists? Is it controlling ownership? Is there a bitmask involved? I need to quickly recall how this plays out in the kernel, and the implications for security and concurrency. I want to make sure I'm not overlooking any obvious potential problems. Let's see what we're dealing with here...
46/3	2026/09/26 19:15	tool	grepper	0m Args: { "Expression": "ipc_permissions", "PathPrefix": "ipc/" } Results: { "Output": "ipc/ipc_sysctl.c=203=static void ipc_set_ownership(struct ctl_table_header head,\n--\nipc/ipc_sysctl.c-215-\nipc/ipc_sysctl.c:216:static int ipc_permissions(struct ctl_table_header head, const struct ctl_table *table)\nipc/ipc_sysctl.c-217-{\n--\nipc/ipc_sysctl.c=249=static struct ctl_table_root set_root = {\nipc/ipc_sysctl.c-250-\t.lookup = set_lookup,\nipc/ipc_sysctl.c:251:\t.permissions = ipc_permissions,\nipc/ipc_sysctl.c-252-\t.set_ownership = ipc_set_ownership,\n" }
47/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16566 output: 36 thoughts: 15 Thoughts: Okay, here's my take on those texts, focusing on the core meaning, as I understand it: Decoding Permissions: IPC and Message Queues Alright, let's dive into the `ipc_permissions` and `mq_permissions` concepts. My initial thought is that we're talking about access control, obviously. Specifically, how we regulate who can interact with Inter-Process Communication (IPC) mechanisms and message queues within the system. I'm immediately thinking about the significance of this. Without proper permissions management, these IPC objects become potential security vulnerabilities. I'm imagining scenarios involving unauthorized processes eavesdropping on, injecting, or maliciously modifying data being shared through these channels. We need robust mechanisms to prevent that. I'll need to look at who is the owner, what are the group settings, and other relevant access control details. It's about protecting data integrity and preventing unauthorized interaction in an environment where processes need to collaborate, but in a controlled manner.
48/3	2026/09/26 19:15	tool	read-file	0m Args: { "File": "ipc/ipc_sysctl.c", "FirstLine": 210, "LineCount": 40 } Results: { "Contents": " 210:\t\tkgid_t ns_root_gid = make_kgid(ns-\u003euser_ns, 0);\n 211:\t\n 212:\t\tuid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;\n 213:\t\tgid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;\n 214:\t}\n 215:\t\n 216:\tstatic int ipc_permissions(struct ctl_table_header head, const struct ctl_table table)\n 217:\t{\n 218:\t\tint mode = table-\u003emode;\n 219:\t\n 220:\t#ifdef CONFIG_CHECKPOINT_RESTORE\n 221:\t\tstruct ipc_namespace *ns =\n 222:\t\t\tcontainer_of(head-\u003eset, struct ipc_namespace, ipc_set);\n 223:\t\n 224:\t\tif (((table-\u003edata == \u0026ns-\u003eids[IPC_SEM_IDS].next_id) \|\|\n 225:\t\t (table-\u003edata == \u0026ns-\u003eids[IPC_MSG_IDS].next_id) \|\|\n 226:\t\t (table-\u003edata == \u0026ns-\u003eids[IPC_SHM_IDS].next_id)) \u0026\u0026\n 227:\t\t checkpoint_restore_ns_capable_noaudit(ns-\u003euser_ns))\n 228:\t\t\tmode = 0666;\n 229:\t\telse\n 230:\t#endif\n 231:\t\t{\n 232:\t\t\tkuid_t ns_root_uid;\n 233:\t\t\tkgid_t ns_root_gid;\n 234:\t\n 235:\t\t\tipc_set_ownership(head, \u0026ns_root_uid, \u0026ns_root_gid);\n 236:\t\n 237:\t\t\tif (uid_eq(current_euid(), ns_root_uid))\n 238:\t\t\t\tmode \u003e\u003e= 6;\n 239:\t\n 240:\t\t\telse if (in_egroup_p(ns_root_gid))\n 241:\t\t\t\tmode \u003e\u003e= 3;\n 242:\t\t}\n 243:\t\n 244:\t\tmode \u0026= 7;\n 245:\t\n 246:\t\treturn (mode \u003c\u003c 6) \| (mode \u003c\u003c 3) \| mode;\n 247:\t}\n 248:\t\n 249:\tstatic struct ctl_table_root set_root = {\n" }
49/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17475 output: 34 thoughts: 742 Thoughts: Analyzing the sysctl Context Resolution Okay, let's break this down. The key here, and what I was picking up on, is how `table->data` is handled within the `proc_sys_call_handler` and, crucially, how it interacts with the permissions check related to checkpoint/restore. Looking at those lines, specifically lines 224-226, I see that this code snippet addresses a scenario where we're dealing with IPC namespaces and checkpoint/restore. The conditional checks `table->data` against offsets related to IPC namespace IDs (semaphores, message queues, shared memory). The critical point is that without the resolution of `table->data` it would be comparing against the global `init_ipc_ns` namespace, which is incorrect. The `else` block, where `sysctl_apply_ctx` is called, is essential because of `ipc_permissions` comparing `table->data`! The patch was needed because if `table->data` isn't resolved, the comparison will fail, since it's pointing to the wrong data. Now, zooming in on `proc_sys_call_handler`, it's clear this function is the core of the sysctl interface for `/proc/sys`. Notice how `table` is initialized from `PROC_I(inode)->sysctl_entry`, and then, importantly, it's passed through `sysctl_apply_ctx`. After the call, the `table` variable may point to the resolved entry, depending on the `CTL_TABLE_F_CTX_DATA` flag. Then the function proceeds to call `table->proc_handler`. Now, the `sysctl_apply_ctx` function itself is the key to understand the resolution. If the `CTL_TABLE_F_CTX_DATA` flag is set, it resolves the pointer by calculating an offset from `head->ctx.tmpl` to `entry->data` and then setting `buf->data` to the corresponding address within `head->ctx.inst`. This mechanism is designed to handle context-specific data within the sysctl tables, probably for cases where the data associated with a sysctl entry is dependent on some structure in the sysctl context. It works by taking an offset between a template structure and an instance struct that has the data. I'm now thinking I need to find all uses of `sysctl_entry` in `fs/proc/proc_sysctl.c`. My next step is to explore the broader use of this context resolution. I need to be sure that the resolution logic is correct across all sysctl operations within `/proc/sys` and not just in this specific IPC namespace case. So, let's find any other uses of the `sysctl_entry` and how it is used.
50/3	2026/09/26 19:15	tool	grepper	0m Args: { "Expression": "sysctl_entry", "PathPrefix": "fs/proc/proc_sysctl.c" } Results: { "Output": "fs/proc/proc_sysctl.c=449=static struct inode proc_sys_make_inode(struct super_block sb,\n--\nfs/proc/proc_sysctl.c-470-\tei-\u003esysctl = head;\nfs/proc/proc_sysctl.c:471:\tei-\u003esysctl_entry = table;\nfs/proc/proc_sysctl.c-472-\thlist_add_head_rcu(\u0026ei-\u003esibling_inodes, \u0026head-\u003einodes);\n--\nfs/proc/proc_sysctl.c=571=static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter,\n--\nfs/proc/proc_sysctl.c-575-\tstruct ctl_table_header head = grab_header(inode);\nfs/proc/proc_sysctl.c:576:\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\nfs/proc/proc_sysctl.c-577-\tstruct ctl_table ctx_entry;\n--\nfs/proc/proc_sysctl.c=650=static int proc_sys_open(struct inode inode, struct file filp)\n--\nfs/proc/proc_sysctl.c-652-\tstruct ctl_table_header head = grab_header(inode);\nfs/proc/proc_sysctl.c:653:\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\nfs/proc/proc_sysctl.c-654-\n--\nfs/proc/proc_sysctl.c=667=static __poll_t proc_sys_poll(struct file filp, poll_table wait)\n--\nfs/proc/proc_sysctl.c-670-\tstruct ctl_table_header head = grab_header(inode);\nfs/proc/proc_sysctl.c:671:\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\nfs/proc/proc_sysctl.c-672-\t__poll_t ret = DEFAULT_POLLMASK;\n--\nfs/proc/proc_sysctl.c=812=static int proc_sys_permission(struct mnt_idmap idmap,\n--\nfs/proc/proc_sysctl.c-831-\nfs/proc/proc_sysctl.c:832:\ttable = PROC_I(inode)-\u003esysctl_entry;\nfs/proc/proc_sysctl.c-833-\tif (!table) / global root - r-xr-xr-x /\n--\nfs/proc/proc_sysctl.c=862=static int proc_sys_getattr(struct mnt_idmap idmap,\n--\nfs/proc/proc_sysctl.c-867-\tstruct ctl_table_header head = grab_header(inode);\nfs/proc/proc_sysctl.c:868:\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\nfs/proc/proc_sysctl.c-869-\n" }
51/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 19635 output: 38 thoughts: 25 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Analyzing System Call Hooks in the /proc Filesystem Alright, let's dive in. I need to refresh my understanding and confirm my assumptions about the hook points within the `/proc` filesystem. Specifically, I want to zero in on how these calls affect performance, security, and traceability: Let's start by looking closely at how `proc_sys_open`, `proc_sys_poll`, and `proc_sys_getattr` are implemented and if they interact in some way. I have to see how each of these system calls interacts with the `/proc` filesystem. I want to see if each hook point might be used for intercepting or modifying system behavior. What are the common use cases for each hook? Are there specific types of data I should anticipate being accessed or manipulated through these entry points?
52/3	2026/09/26 19:15	tool	read-file	0m Args: { "File": "fs/proc/proc_sysctl.c", "FirstLine": 650, "LineCount": 45 } Results: { "Contents": " 650:\tstatic int proc_sys_open(struct inode inode, struct file filp)\n 651:\t{\n 652:\t\tstruct ctl_table_header head = grab_header(inode);\n 653:\t\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\n 654:\t\n 655:\t\t/* sysctl was unregistered /\n 656:\t\tif (IS_ERR(head))\n 657:\t\t\treturn PTR_ERR(head);\n 658:\t\n 659:\t\tif (table-\u003epoll)\n 660:\t\t\tfilp-\u003eprivate_data = proc_sys_poll_event(table-\u003epoll);\n 661:\t\n 662:\t\tsysctl_head_finish(head);\n 663:\t\n 664:\t\treturn 0;\n 665:\t}\n 666:\t\n 667:\tstatic __poll_t proc_sys_poll(struct file filp, poll_table wait)\n 668:\t{\n 669:\t\tstruct inode inode = file_inode(filp);\n 670:\t\tstruct ctl_table_header head = grab_header(inode);\n 671:\t\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\n 672:\t\t__poll_t ret = DEFAULT_POLLMASK;\n 673:\t\tunsigned long event;\n 674:\t\n 675:\t\t/* sysctl was unregistered */\n 676:\t\tif (IS_ERR(head))\n 677:\t\t\treturn EPOLLERR \| EPOLLHUP;\n 678:\t\n 679:\t\tif (!table-\u003eproc_handler)\n 680:\t\t\tgoto out;\n 681:\t\n 682:\t\tif (!table-\u003epoll)\n 683:\t\t\tgoto out;\n 684:\t\n 685:\t\tevent = (unsigned long)filp-\u003eprivate_data;\n 686:\t\tpoll_wait(filp, \u0026table-\u003epoll-\u003ewait, wait);\n 687:\t\n 688:\t\tif (event != atomic_read(\u0026table-\u003epoll-\u003eevent)) {\n 689:\t\t\tfilp-\u003eprivate_data = proc_sys_poll_event(table-\u003epoll);\n 690:\t\t\tret = EPOLLIN \| EPOLLRDNORM \| EPOLLERR \| EPOLLPRI;\n 691:\t\t}\n 692:\t\n 693:\tout:\n 694:\t\tsysctl_head_finish(head);\n" }
53/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 20554 output: 38 thoughts: 12 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, and delivered as a first-person summary: Digging into `proc_sys_getattr` Alright, so I'm thinking about the kernel-level attribute retrieval process... specifically, I want to take a closer look at `proc_sys_getattr`. I've got a hunch about something going on with how we're handling the system calls or, more likely, how we're caching attributes in procfs and need to make sure we aren't creating a bottleneck. I’ve been looking at the tracepoints and feel like this is the next logical function to dive into. Time to get my hands dirty and understand exactly how `proc_sys_getattr` interacts with the vfs layer and how we resolve the data that get's returned. Is there something we're missing in the locking, caching, or data validation? Let's check it.
54/3	2026/09/26 19:15	tool	read-file	0m Args: { "File": "fs/proc/proc_sysctl.c", "FirstLine": 860, "LineCount": 45 } Results: { "Contents": " 860:\t}\n 861:\t\n 862:\tstatic int proc_sys_getattr(struct mnt_idmap idmap,\n 863:\t\t\t\t const struct path path, struct kstat stat,\n 864:\t\t\t\t u32 request_mask, unsigned int query_flags)\n 865:\t{\n 866:\t\tstruct inode inode = d_inode(path-\u003edentry);\n 867:\t\tstruct ctl_table_header head = grab_header(inode);\n 868:\t\tconst struct ctl_table table = PROC_I(inode)-\u003esysctl_entry;\n 869:\t\n 870:\t\tif (IS_ERR(head))\n 871:\t\t\treturn PTR_ERR(head);\n 872:\t\n 873:\t\tgeneric_fillattr(\u0026nop_mnt_idmap, request_mask, inode, stat);\n 874:\t\tif (table)\n 875:\t\t\tstat-\u003emode = (stat-\u003emode \u0026 S_IFMT) \| table-\u003emode;\n 876:\t\n 877:\t\tsysctl_head_finish(head);\n 878:\t\treturn 0;\n 879:\t}\n 880:\t\n 881:\tstatic const struct file_operations proc_sys_file_operations = {\n 882:\t\t.open\t\t= proc_sys_open,\n 883:\t\t.poll\t\t= proc_sys_poll,\n 884:\t\t.read_iter\t= proc_sys_read,\n 885:\t\t.write_iter\t= proc_sys_write,\n 886:\t\t.splice_read\t= copy_splice_read,\n 887:\t\t.splice_write\t= iter_file_splice_write,\n 888:\t\t.llseek\t\t= default_llseek,\n 889:\t};\n 890:\t\n 891:\tstatic const struct file_operations proc_sys_dir_file_operations = {\n 892:\t\t.read\t\t= generic_read_dir,\n 893:\t\t.iterate_shared\t= proc_sys_readdir,\n 894:\t\t.llseek\t\t= generic_file_llseek,\n 895:\t};\n 896:\t\n 897:\tstatic const struct inode_operations proc_sys_inode_operations = {\n 898:\t\t.permission\t= proc_sys_permission,\n 899:\t\t.setattr\t= proc_sys_setattr,\n 900:\t\t.getattr\t= proc_sys_getattr,\n 901:\t};\n 902:\t\n 903:\tstatic const struct inode_operations proc_sys_dir_operations = {\n 904:\t\t.lookup\t\t= proc_sys_lookup,\n" }
55/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21522 output: 28 thoughts: 79 Thoughts: Here's my summary, as I see it: Analyzing `proc_sys` Table Usage Okay, so I'm digging into how the `proc_sys` file system utilizes its `table` structures. It looks like `proc_sys_open`, `proc_sys_poll`, and `proc_sys_getattr` are only referencing `table->poll` and `table->mode`. That's good to know, keeps it simple, less to worry about in that particular set of functions. But, I need to be sure I understand the full picture, so I can't stop here. The real question I need answered is whether other functions, such as `BPF_CGROUP_RUN_PROG_SYSCTL`, use other parts of the table, specifically `table->data`. I should check the implementation of that function to see how it uses `table` to be certain I have a complete understanding of how the `proc_sys` table structure is used. I need to make sure I don't miss anything that depends on `table->data`. Let's see how that one is written.
56/3	2026/09/26 19:15	tool	grepper	0m Args: { "Expression": "BPF_CGROUP_RUN_PROG_SYSCTL" } Results: { "Output": "fs/proc/proc_sysctl.c=571=static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter,\n--\nfs/proc/proc_sysctl.c-614-\nfs/proc/proc_sysctl.c:615:\terror = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, \u0026kbuf, \u0026count,\nfs/proc/proc_sysctl.c-616-\t\t\t\t\t \u0026iocb-\u003eki_pos);\n--\ninclude/linux/bpf-cgroup.h=180=static inline bool cgroup_bpf_sock_enabled(struct sock sk,\n--\ninclude/linux/bpf-cgroup.h-368-\ninclude/linux/bpf-cgroup.h:369:#define BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, count, pos) \\\ninclude/linux/bpf-cgroup.h-370-({\t\t\t\t\t\t\t\t\t \\\n--\ninclude/linux/bpf-cgroup.h=477=static inline int bpf_percpu_cgroup_storage_update(struct bpf_map map,\n--\ninclude/linux/bpf-cgroup.h-505-#define BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(atype, major, minor, access) ({ 0; })\ninclude/linux/bpf-cgroup.h:506:#define BPF_CGROUP_RUN_PROG_SYSCTL(head,table,write,buf,count,pos) ({ 0; })\ninclude/linux/bpf-cgroup.h-507-#define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, \\\n" }
57/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 22328 output: 39 thoughts: 37 Thoughts: Okay, let's dive into this. Here's my take on understanding `BPF_CGROUP_RUN_PROG_SYSCTL`, focusing on how I'd approach its analysis. Analyzing `BPF_CGROUP_RUN_PROG_SYSCTL` in `linux/bpf-cgroup.h` Alright, so I need to figure out what this `BPF_CGROUP_RUN_PROG_SYSCTL` does. Clearly, it's something related to BPF programs and cgroups, given the naming convention and the file path. My first instinct, as always, is to treat this as a signal and start building context from the code. I need to understand this `SYSCTL` first. I'll need to know where it's used. What does the kernel do with this? I'm thinking: * Purpose: Given the name, I'd immediately infer that this deals with running a BPF program from within a cgroup context in response to a sysctl configuration. This likely means some kind of runtime interaction, potentially allowing administrators to dynamically alter the behavior of a cgroup based on system state. * Implementation: Now, I'm thinking about the implementation details. I'm imagining it's some sort of system call, or some internal kernel mechanism, that triggers the execution of a BPF program. I'll be looking for where this constant is defined and used. I'll need to trace it down. Is it a flag, an action code, or something else entirely? The definition will give me the first clue. Next, I'll need to follow the usage. Where does the kernel actually check this constant? What functions reference it? * Usage Context: My understanding is that the cgroup-BPF integration would be used for very specific tasks - resource control, monitoring, and potentially enforcement. It's likely that a `SYSCTL` would be used to control the execution environment of a cgroup. For instance, being able to enable or disable the BPF program, or perhaps inject certain configuration parameters into the program runtime. * Security Concerns: My mind immediately jumps to security implications. With a feature that allows executing code from sysctl, I anticipate the importance of carefully scrutinizing any code that uses this and I'll look for checks to validate inputs and to prevent privilege escalation. This is kernel code we're talking about, so malicious actors could attempt to exploit any vulnerabilities present. In essence, I'll need to trace the usage of this constant to fully understand its function. I'll need to consider its context, its potential impact, and its security implications. I'm expecting some sophisticated interactions between BPF, cgroups, and system configuration, all with a critical focus on security and resource management. Let's start digging!
58/3	2026/09/26 19:15	tool	read-file	0m Args: { "File": "include/linux/bpf-cgroup.h", "FirstLine": 368, "LineCount": 40 } Results: { "Contents": " 368:\t\n 369:\t#define BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, count, pos) \\\n 370:\t({\t\t\t\t\t\t\t\t\t \\\n 371:\t\tint __ret = 0;\t\t\t\t\t\t\t \\\n 372:\t\tif (cgroup_bpf_enabled(CGROUP_SYSCTL))\t\t\t \\\n 373:\t\t\t__ret = __cgroup_bpf_run_filter_sysctl(head, table, write, \\\n 374:\t\t\t\t\t\t\t buf, count, pos, \\\n 375:\t\t\t\t\t\t\t CGROUP_SYSCTL); \\\n 376:\t\t__ret;\t\t\t\t\t\t\t\t \\\n 377:\t})\n 378:\t\n 379:\t#define BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock, level, optname, optval, optlen, \\\n 380:\t\t\t\t\t kernel_optval)\t\t\t \\\n 381:\t({\t\t\t\t\t\t\t\t\t \\\n 382:\t\tint __ret = 0;\t\t\t\t\t\t\t \\\n 383:\t\tif (cgroup_bpf_enabled(CGROUP_SETSOCKOPT) \u0026\u0026\t\t\t \\\n 384:\t\t cgroup_bpf_sock_enabled(sock, CGROUP_SETSOCKOPT))\t\t \\\n 385:\t\t\t__ret = __cgroup_bpf_run_filter_setsockopt(sock, level,\t \\\n 386:\t\t\t\t\t\t\t\t optname, optval, \\\n 387:\t\t\t\t\t\t\t\t optlen,\t \\\n 388:\t\t\t\t\t\t\t\t kernel_optval); \\\n 389:\t\t__ret;\t\t\t\t\t\t\t\t \\\n 390:\t})\n 391:\t\n 392:\t#define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, optlen, \\\n 393:\t\t\t\t\t max_optlen, retval)\t\t \\\n 394:\t({\t\t\t\t\t\t\t\t\t \\\n 395:\t\tint __ret = retval;\t\t\t\t\t\t \\\n 396:\t\tif (cgroup_bpf_enabled(CGROUP_GETSOCKOPT) \u0026\u0026\t\t\t \\\n 397:\t\t cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT))\t\t \\\n 398:\t\t\tif (!(sock)-\u003esk_prot-\u003ebpf_bypass_getsockopt \|\|\t\t \\\n 399:\t\t\t !INDIRECT_CALL_INET_1((sock)-\u003esk_prot-\u003ebpf_bypass_getsockopt, \\\n 400:\t\t\t\t\t\ttcp_bpf_bypass_getsockopt,\t \\\n 401:\t\t\t\t\t\tlevel, optname))\t\t \\\n 402:\t\t\t\t__ret = __cgroup_bpf_run_filter_getsockopt(\t \\\n 403:\t\t\t\t\tsock, level, optname, optval, optlen,\t \\\n 404:\t\t\t\t\tmax_optlen, retval);\t\t\t \\\n 405:\t\t__ret;\t\t\t\t\t\t\t\t \\\n 406:\t})\n 407:\t\n" }
59/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23809 output: 27 thoughts: 19 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Analyzing `__cgroup_bpf_run_filter_sysctl` Alright, let's dive into this. I'm taking a look at `__cgroup_bpf_run_filter_sysctl`. This suggests we're dealing with a sysctl interface related to BPF filtering within the cgroup context. I need to understand how this function is structured, what inputs it takes, and crucially, what its security implications are. My primary concern, as always, is potential privilege escalation or denial-of-service vulnerabilities. I'll need to scrutinize how it handles user-provided BPF programs, especially their interaction with the cgroup hierarchy and resource limits. Is there adequate validation of the BPF code to prevent malicious behavior? Are there any race conditions that could be exploited? And, how does this sysctl interact with other related BPF and cgroup subsystems? I'll probably start by looking at its implementation, cross-referencing it with the relevant documentation, and then running it through some static analysis tools to identify potential weaknesses. I'll also want to look at its call graph and see who is calling it, and from where, looking for points of entry and egress.
60/3	2026/09/26 19:15	tool	grepper	0m Args: { "Expression": "__cgroup_bpf_run_filter_sysctl" } Results: { "Output": "include/linux/bpf-cgroup.h=133=int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,\n--\ninclude/linux/bpf-cgroup.h-135-\ninclude/linux/bpf-cgroup.h:136:int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header head,\ninclude/linux/bpf-cgroup.h-137-\t\t\t\t const struct ctl_table table, int write,\n--\ninclude/linux/bpf-cgroup.h=180=static inline bool cgroup_bpf_sock_enabled(struct sock sk,\n--\ninclude/linux/bpf-cgroup.h-372-\tif (cgroup_bpf_enabled(CGROUP_SYSCTL))\t\t\t \\\ninclude/linux/bpf-cgroup.h:373:\t\t__ret = __cgroup_bpf_run_filter_sysctl(head, table, write, \\\ninclude/linux/bpf-cgroup.h-374-\t\t\t\t\t\t buf, count, pos, \\\n--\nkernel/bpf/cgroup.c=1926=const struct bpf_verifier_ops cg_dev_verifier_ops = {\n--\nkernel/bpf/cgroup.c-1931-/\nkernel/bpf/cgroup.c:1932: __cgroup_bpf_run_filter_sysctl - Run a program on sysctl\nkernel/bpf/cgroup.c-1933- \n--\nkernel/bpf/cgroup.c-1951- /\nkernel/bpf/cgroup.c:1952:int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header head,\nkernel/bpf/cgroup.c-1953-\t\t\t\t const struct ctl_table table, int write,\n" }
61/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 24620 output: 38 thoughts: 22 Thoughts: Here's a summary of my thought process, expert to expert: Investigating a Potential BPF/cgroup Issue Okay, so I need to dive into this. Based on the issue description, my intuition tells me there might be something related to cgroups and BPF. My first step is to zero in on a potential area of concern. Let's start with the kernel source code. Specifically, the BPF and cgroup interaction code. I'm going to jump straight to `kernel/bpf/cgroup.c`, and I'll begin by focusing on line 1952. My experience dictates that this is a reasonable starting point when debugging these kinds of interactions. I will see what is being done at that line and try to understand the context.
62/3	2026/09/26 19:15	tool	read-file	0m Args: { "File": "kernel/bpf/cgroup.c", "FirstLine": 1950, "LineCount": 45 } Results: { "Contents": "1950:\t * returned value != 1 during execution. In all other cases 0 is returned.\n1951:\t /\n1952:\tint __cgroup_bpf_run_filter_sysctl(struct ctl_table_header head,\n1953:\t\t\t\t\t const struct ctl_table table, int write,\n1954:\t\t\t\t\t char buf, size_t pcount, loff_t ppos,\n1955:\t\t\t\t\t enum cgroup_bpf_attach_type atype)\n1956:\t{\n1957:\t\tstruct bpf_sysctl_kern ctx = {\n1958:\t\t\t.head = head,\n1959:\t\t\t.table = table,\n1960:\t\t\t.write = write,\n1961:\t\t\t.ppos = ppos,\n1962:\t\t\t.cur_val = NULL,\n1963:\t\t\t.cur_len = PAGE_SIZE,\n1964:\t\t\t.new_val = NULL,\n1965:\t\t\t.new_len = 0,\n1966:\t\t\t.new_updated = 0,\n1967:\t\t};\n1968:\t\tstruct cgroup cgrp;\n1969:\t\tloff_t pos = 0;\n1970:\t\tint ret;\n1971:\t\n1972:\t\tctx.cur_val = kmalloc_track_caller(ctx.cur_len, GFP_KERNEL);\n1973:\t\tif (!ctx.cur_val \|\|\n1974:\t\t table-\u003eproc_handler(table, 0, ctx.cur_val, \u0026ctx.cur_len, \u0026pos)) {\n1975:\t\t\t/* Let BPF program decide how to proceed. /\n1976:\t\t\tctx.cur_len = 0;\n1977:\t\t}\n1978:\t\n1979:\t\tif (write \u0026\u0026 buf \u0026\u0026 pcount) {\n1980:\t\t\t/ BPF program should be able to override new value with a\n1981:\t\t\t * buffer bigger than provided by user.\n1982:\t\t\t /\n1983:\t\t\tctx.new_val = kmalloc_track_caller(PAGE_SIZE, GFP_KERNEL);\n1984:\t\t\tctx.new_len = min_t(size_t, PAGE_SIZE, pcount);\n1985:\t\t\tif (ctx.new_val) {\n1986:\t\t\t\tmemcpy(ctx.new_val, buf, ctx.new_len);\n1987:\t\t\t} else {\n1988:\t\t\t\t/ Let BPF program decide how to proceed. */\n1989:\t\t\t\tctx.new_len = 0;\n1990:\t\t\t}\n1991:\t\t}\n1992:\t\n1993:\t\trcu_read_lock();\n1994:\t\tcgrp = task_dfl_cgroup(current);\n" }
63/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25584 output: 20 thoughts: 2676 Thoughts: BPF Sysctl Filter Analysis: Context and Data Handling Alright, let's break this down. The core is the sysctl filter that calls `table->proc_handler`. The patch is about how the `ctl_table` data, and particularly its associated context, is handled. Previously, there was a `kmemdup` of `ipc_sysctls` and `mq_sysctls` which led to dynamic allocation on the slab cache. This patch changes that by making `ipc_sysctls` (and others) static and read-only. The key is `__register_sysctl_table_ctx`. Instead of `kmemdup`, it now registers these static `ctl_table` arrays. The crucial part is the `sysctl_apply_ctx` function. When a sysctl entry is accessed, it applies a context to the table entry. The context is encapsulated in `struct ctl_table_header` which now copies a `struct sysctl_context` from the stack. `sysctl_apply_ctx` uses this context to potentially modify the data pointer (`entry->data`). It copies the whole `struct ctl_table` into a local buffer (`buf`). If `CTL_TABLE_F_CTX_DATA` is set, it calculates an offset (`off`) between the `entry->data` and the context template (`header->ctx.tmpl`) and sets `buf->data` to point to a corresponding location in the context instance (`header->ctx.inst`). This is where the magic happens: instead of the original `.rodata` address, data can now be pointed to within the context. Let's look at `struct ctl_table`. The crucial field is `data`, which is what this patch is manipulating. Also, the `proc_handler` is being set up correctly, it seems. Crucially, there's a local, uninitialized `struct ctl_table ctx_entry` on the stack. The function `sysctl_apply_ctx` copies from the static `entry` to this local `buf` (`ctx_entry`). It seems as though this `ctx_entry` is never copied to userspace; the kernel pointer to `table` is what is used. The `kbuf` that gets copied to user space in `proc_sys_call_handler` is allocated using `kvzalloc`, meaning it's zero-initialized. Its data is then populated by the `table->proc_handler`. The concern is that `buf->data` could point to something unexpected. However, it's relative to the context, so the offset calculation prevents this. The context instance is initialized. `SYSCTL_CTX(ns, &init_ipc_ns)` ensures both `.inst` and `.tmpl` are fully initialized. The code includes checks in `sysctl_check_table` to make sure the context is properly set up. It checks if the `data` pointer is valid and if there's a context available if `CTL_TABLE_F_CTX_DATA` is set. If the context is missing when needed, registration will fail. The code assumes that `ctl_table` entries are either `static` or `static const`, thus the padding (if any) is zero-initialized and any uninitialized bits in `flags` will be zero. I need to be careful when there is no context flag, in that the static `entry` pointer is returned directly, with no changes or copies. No issues there either. I'll need to remember to check for dynamically allocated ones.
64/3	2026/09/26 19:15	tool	grepper	0m Args: { "Expression": "kzalloc.ctl_table" } Results:* { "Output": "arch/s390/appldata/appldata_base.c=347=int appldata_register_ops(struct appldata_ops ops)\n--\narch/s390/appldata/appldata_base.c-351-\narch/s390/appldata/appldata_base.c:352:\tops-\u003ectl_table = kzalloc_objs(struct ctl_table, 1);\narch/s390/appldata/appldata_base.c-353-\tif (!ops-\u003ectl_table)\n--\nfs/proc/proc_sysctl.c=1218=static struct ctl_table_header new_links(struct ctl_dir dir, struct ctl_table_header head)\n--\nfs/proc/proc_sysctl.c-1231-\nfs/proc/proc_sysctl.c:1232:\tlinks = kzalloc(sizeof(struct ctl_table_header) +\nfs/proc/proc_sysctl.c-1233-\t\t\tsizeof(struct ctl_node)head-\u003ectl_table_size +\n--\nfs/proc/proc_sysctl.c=1412=struct ctl_table_header __register_sysctl_table_ctx(\n--\nfs/proc/proc_sysctl.c-1421-\nfs/proc/proc_sysctl.c:1422:\theader = kzalloc(sizeof(struct ctl_table_header) +\nfs/proc/proc_sysctl.c-1423-\t\t\t sizeof(struct ctl_node)*table_size, GFP_KERNEL_ACCOUNT);\n" }
65/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29448 output: 20 thoughts: 18 Thoughts: Okay, here's my summary, presented as a stream of thought: Checking for `kmalloc` of `ctl_table` Alright, let's get down to business. My first step in this analysis is to rigorously check for the presence of any uses of `kmalloc` associated with `ctl_table`. I need to understand how this crucial data structure is being allocated and managed. This initial check will give me a critical foundation for further exploration; seeing this usage, or lack thereof, immediately points to particular avenues for me to focus on. Is it using a custom allocator? Are there any potential memory leaks here? Knowing the allocation method is fundamental to understanding the overall architecture and potential vulnerabilities associated with `ctl_table`.
66/3	2026/09/26 19:15	tool	grepper	0m Error: no matches Args: { "Expression": "kmalloc.ctl_table" } Results:* { "error": "no matches" }
67/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29653 output: 21 thoughts: 17 Thoughts: Okay, let's dive into this. Here's my thought process laid out: Checking `kmemdup` of `ctl_table` Right, before I proceed with any further analysis or modifications, I need to make absolutely sure that the `ctl_table` has been properly handled using `kmemdup`. This is crucial. If the table isn't duplicated correctly, any changes I make to a potentially shared copy could lead to massive problems down the line, including memory corruption, security vulnerabilities, or unpredictable kernel behavior. I have to avoid making assumptions about the state of this structure. This initial check is non-negotiable. It’s a foundational safety measure that needs to be ironclad before I can even think about modifying the contents or usage of the `ctl_table`. I am expecting to see the duplicate is working as intended.
68/3	2026/09/26 19:15	tool	grepper	0m Args: { "Expression": "kmemdup.ctl_table" } Results:* { "Output": "net/ieee802154/6lowpan/reassembly.c=362=static int __net_init lowpan_frags_ns_sysctl_register(struct net net)\n--\nnet/ieee802154/6lowpan/reassembly.c-371-\tif (!net_eq(net, \u0026init_net)) {\nnet/ieee802154/6lowpan/reassembly.c:372:\t\ttable = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),\nnet/ieee802154/6lowpan/reassembly.c-373-\t\t\t\tGFP_KERNEL);\n--\nnet/ipv4/ip_fragment.c=588=static int __net_init ip4_frags_ns_ctl_register(struct net net)\n--\nnet/ipv4/ip_fragment.c-594-\tif (!net_eq(net, \u0026init_net)) {\nnet/ipv4/ip_fragment.c:595:\t\ttable = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);\nnet/ipv4/ip_fragment.c-596-\t\tif (!table)\n--\nnet/ipv6/netfilter/nf_conntrack_reasm.c=67=static int nf_ct_frag6_sysctl_register(struct net net)\n--\nnet/ipv6/netfilter/nf_conntrack_reasm.c-74-\tif (!net_eq(net, \u0026init_net)) {\nnet/ipv6/netfilter/nf_conntrack_reasm.c:75:\t\ttable = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),\nnet/ipv6/netfilter/nf_conntrack_reasm.c-76-\t\t\t\tGFP_KERNEL);\n--\nnet/ipv6/reassembly.c=456=static int __net_init ip6_frags_ns_sysctl_register(struct net net)\n--\nnet/ipv6/reassembly.c-462-\tif (!net_eq(net, \u0026init_net)) {\nnet/ipv6/reassembly.c:463:\t\ttable = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);\nnet/ipv6/reassembly.c-464-\t\tif (!table)\n--\nnet/mptcp/ctrl.c=382=static int mptcp_pernet_new_table(struct net net, struct mptcp_pernet pernet)\n--\nnet/mptcp/ctrl.c-388-\tif (!net_eq(net, \u0026init_net)) {\nnet/mptcp/ctrl.c:389:\t\ttable = kmemdup(table, sizeof(mptcp_sysctl_table), GFP_KERNEL);\nnet/mptcp/ctrl.c-390-\t\tif (!table)\n--\nnet/netfilter/nf_conntrack_standalone.c=1003=static int nf_conntrack_standalone_init_sysctl(struct net net)\n--\nnet/netfilter/nf_conntrack_standalone.c-1010-\nnet/netfilter/nf_conntrack_standalone.c:1011:\ttable = kmemdup(nf_ct_sysctl_table, sizeof(nf_ct_sysctl_table),\nnet/netfilter/nf_conntrack_standalone.c-1012-\t\t\tGFP_KERNEL);\n--\nnet/netfilter/nf_hooks_lwtunnel.c=67=static int __net_init nf_lwtunnel_net_init(struct net net)\n--\nnet/netfilter/nf_hooks_lwtunnel.c-73-\tif (!net_eq(net, \u0026init_net)) {\nnet/netfilter/nf_hooks_lwtunnel.c:74:\t\ttable = kmemdup(nf_lwtunnel_sysctl_table,\nnet/netfilter/nf_hooks_lwtunnel.c-75-\t\t\t\tsizeof(nf_lwtunnel_sysctl_table),\n--\nnet/netfilter/nf_log.c=487=static int netfilter_log_sysctl_init(struct net net)\n--\nnet/netfilter/nf_log.c-493-\tif (!net_eq(net, \u0026init_net)) {\nnet/netfilter/nf_log.c:494:\t\ttable = kmemdup(nf_log_sysctl_table,\nnet/netfilter/nf_log.c-495-\t\t\t\t sizeof(nf_log_sysctl_table),\n--\nnet/rds/tcp.c=612=static __net_init int rds_tcp_init_net(struct net net)\n--\nnet/rds/tcp.c-627-\t} else {\nnet/rds/tcp.c:628:\t\ttbl = kmemdup(rds_tcp_sysctl_table,\nnet/rds/tcp.c-629-\t\t\t sizeof(rds_tcp_sysctl_table), GFP_KERNEL);\n" }
69/3	2026/09/26 19:15	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31149 output: 27 thoughts: 324 Thoughts: Analyzing Potential Vulnerabilities in sysctl_apply_ctx Okay, so I'm looking at these `kmemdup` calls from static tables, zero-initialized, and now I'm digging into this patch. Let's see... we have `sysctl_apply_ctx`. Right, it returns either the original entry if it's not context-specific, or a resolved copy in the buffer. The critical bit here is the `off` calculation: `(const char )entry->data - (const char )head->ctx.tmpl`. I'm starting to think... is there a way this offset could result in an invalid or out-of-bounds address? That's what I am asking myself. If it's OOB, KASAN should catch it, right? But... what about uninitialized memory? Could `(char *)head->ctx.inst + off` potentially point to uninitialized memory? That's the real worry here. Uninitialized memory can lead to all sorts of fun, potentially exploitable, behavior. Now, where is `head->ctx.inst` coming from? And where is `head->ctx.tmpl` coming from? I need to track down the allocation of `ns` in `setup_ipc_sysctls`. Let's see... it looks like `ns` is allocated in `create_ipc_ns`! Okay, back to `create_ipc_ns`...
70/3	2026/09/26 19:16	tool	grepper	0m Args: { "Expression": "create_ipc_ns", "PathPrefix": "ipc/" } Results: { "Output": "ipc/namespace.c=34=static void dec_ipc_namespaces(struct ucounts ucounts)\n--\nipc/namespace.c-38-\nipc/namespace.c:39:static struct ipc_namespace create_ipc_ns(struct user_namespace user_ns,\nipc/namespace.c-40-\t\t\t\t\t struct ipc_namespace old_ns)\n--\nipc/namespace.c=111=struct ipc_namespace *copy_ipcs(u64 flags,\n--\nipc/namespace.c-115-\t\treturn get_ipc_ns(ns);\nipc/namespace.c:116:\treturn create_ipc_ns(user_ns, ns);\nipc/namespace.c-117-}\n" }
71/3	2026/09/26 19:16	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31995 output: 32 thoughts: 19 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into the IPC Namespace Creation Alright, let's get down to brass tacks. I need to understand the mechanics behind creating an IPC namespace, so I'm heading straight for the `create_ipc_ns` function in `ipc/namespace.c`. This is where the core logic must reside. I want to see how this crucial structure is initialized, what resources are allocated, and how the namespace is integrated into the overall kernel architecture. I'm looking for the details that will help me reason about its lifecycle, how it interacts with other kernel subsystems, and potential implications for IPC resource management. Time to dig in and see how the sausage is made.
72/3	2026/09/26 19:16	tool	read-file	0m Args: { "File": "ipc/namespace.c", "FirstLine": 38, "LineCount": 55 } Results: { "Contents": " 38:\t\n 39:\tstatic struct ipc_namespace create_ipc_ns(struct user_namespace user_ns,\n 40:\t\t\t\t\t\t struct ipc_namespace old_ns)\n 41:\t{\n 42:\t\tstruct ipc_namespace ns;\n 43:\t\tstruct ucounts ucounts;\n 44:\t\tint err;\n 45:\t\n 46:\t\terr = -ENOSPC;\n 47:\t again:\n 48:\t\tucounts = inc_ipc_namespaces(user_ns);\n 49:\t\tif (!ucounts) {\n 50:\t\t\t/\n 51:\t\t\t * IPC namespaces are freed asynchronously, by free_ipc_work.\n 52:\t\t\t * If frees were pending, flush_work will wait, and\n 53:\t\t\t * return true. Fail the allocation if no frees are pending.\n 54:\t\t\t */\n 55:\t\t\tif (flush_work(\u0026free_ipc_work))\n 56:\t\t\t\tgoto again;\n 57:\t\t\tgoto fail;\n 58:\t\t}\n 59:\t\n 60:\t\terr = -ENOMEM;\n 61:\t\tns = kzalloc_obj(struct ipc_namespace, GFP_KERNEL_ACCOUNT);\n 62:\t\tif (ns == NULL)\n 63:\t\t\tgoto fail_dec;\n 64:\t\n 65:\t\terr = ns_common_init(ns);\n 66:\t\tif (err)\n 67:\t\t\tgoto fail_free;\n 68:\t\n 69:\t\tns_tree_gen_id(ns);\n 70:\t\tns-\u003euser_ns = get_user_ns(user_ns);\n 71:\t\tns-\u003eucounts = ucounts;\n 72:\t\n 73:\t\terr = mq_init_ns(ns);\n 74:\t\tif (err)\n 75:\t\t\tgoto fail_put;\n 76:\t\n 77:\t\terr = -ENOMEM;\n 78:\t\tif (!setup_mq_sysctls(ns))\n 79:\t\t\tgoto fail_mq_mount;\n 80:\t\n 81:\t\tif (!setup_ipc_sysctls(ns))\n 82:\t\t\tgoto fail_mq_sysctls;\n 83:\t\n 84:\t\terr = msg_init_ns(ns);\n 85:\t\tif (err)\n 86:\t\t\tgoto fail_ipc;\n 87:\t\n 88:\t\tsem_init_ns(ns);\n 89:\t\tshm_init_ns(ns);\n 90:\t\tns_tree_add_raw(ns);\n 91:\t\n 92:\t\treturn ns;\n" }
73/3	2026/09/26 19:16	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 32892 output: 28 thoughts: 1222 Thoughts: Analyzing Potential Uninitialized Memory in sysctl Context Okay, so I'm looking at this code and immediately I see `ns = kzalloc_obj(...)`. Good, `ns` is zeroed out right away. That's a solid start. Let me just confirm that the initialization order in relation to the `setup_ipc_sysctls`, `msg_init_ns`, `sem_init_ns`, and `shm_init_ns` calls is as expected, seems the existing order is correct. The values accessed via sysctl from `ns` are already present. Now, I'm concerned about `struct ctl_table ctx_entry;` in `proc_sys_call_handler` and `proc_sys_permission`. Could this be a source of uninitialized memory access? Let's trace it. Within `proc_sys_call_handler`, I find: ```c static ssize_t proc_sys_call_handler(struct kiocb iocb, struct iov_iter iter, int write) { struct inode inode = file_inode(iocb->ki_filp); struct ctl_table_header head = grab_header(inode); const struct ctl_table table = PROC_I(inode)->sysctl_entry; struct ctl_table ctx_entry; ... table = sysctl_apply_ctx(head, table, &ctx_entry); ``` Let's dive into `sysctl_apply_ctx`: ```c static const struct ctl_table sysctl_apply_ctx(struct ctl_table_header head, const struct ctl_table entry, struct ctl_table buf) { ptrdiff_t off; if (!(entry->flags & CTL_TABLE_F_CTX_DATA)) return entry; off = (const char )entry->data - (const char )head->ctx.tmpl; buf = entry; buf->data = (char )head->ctx.inst + off; return buf; } ``` Okay, if `!(entry->flags & CTL_TABLE_F_CTX_DATA)`, the function simply returns the original `entry` without touching `buf` or `ctx_entry`. So, `table` in the caller would remain unchanged, pointing to the original entry. This is safe. If `(entry->flags & CTL_TABLE_F_CTX_DATA)`, `buf = entry` fully copies the contents of `entry` into `buf`. Then, `buf->data` gets overwritten. Crucially, `buf` (and therefore `ctx_entry` in the caller) is completely overwritten. The question is, is `entry` fully initialized? Here's the key: `entry` points to a registered `ctl_table`, specifically `ipc_sysctls[]` or `mq_sysctls[]` in this case. These are static const objects. In C, static objects are zero-initialized by default, meaning every byte is initialized. Therefore, every byte of `entry` is initialized, and thus, every byte of `buf` and `ctx_entry` becomes initialized. No uninitialized memory is left. But, a compiler could theoretically mishandle struct assignment. Does the compiler copy padding? A struct assignment (`dst = src;`) is typically compiled to a `memcpy` or a sequence of `mov` instructions. Even if the compiler skips padding bytes, these are not semantically accessed by C code unless a `memcpy` or `copy_to_user` of the whole struct is happening. The question then, is whether `table` or `ctx_entry` (the buffer that gets updated in `sysctl_apply_ctx`) are ever copied to userspace, compared with `memcmp`, or written to a buffer sent to a user. Let's check where `table` is used* within `proc_sys_call_handler`: 1. `sysctl_perm(head, table, ...)` -> Accesses `table->mode` or calls `root->permissions(head, table)` which accesses `table->data`, `table->mode`. 2. `if (!table->proc_handler)` -> Accesses `table->proc_handler`. 3. `BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count, &iocb->ki_pos)` -> creates a `struct bpf_sysctl_kern ctx` with `.table =
74/3	2026/09/26 19:16	tool	grepper	0m Args: { "Expression": "ctx-\u003etable", "PathPrefix": "kernel/bpf/" } Results: { "Output": "kernel/bpf/cgroup.c=2306=BPF_CALL_4(bpf_sysctl_get_name, struct bpf_sysctl_kern , ctx, char , buf,\n--\nkernel/bpf/cgroup.c-2321-\nkernel/bpf/cgroup.c:2322:\tret = strscpy(buf, ctx-\u003etable-\u003eprocname, buf_len);\nkernel/bpf/cgroup.c-2323-\n" }
75/3	2026/09/26 19:16	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35297 output: 30 thoughts: 24 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, and written as if they were my own: Investigating Potential `table` Usage in `kernel/bpf/cgroup.c` Alright, let's dive in. I need to get a handle on all potential uses of "table" within `kernel/bpf/cgroup.c`. This isn't just a casual search; I'm looking for specific implementations, interactions, maybe even subtle design patterns related to how tables are handled within that particular module. I'm expecting to see things like: table lookups, table updates (insertions, deletions, modifications), table creation and destruction, maybe even indirect references or uses of helpers operating on some table data structure. This could be a BPF map, a control structure, anything really. I need to be methodical. Let's see what turns up.
76/3	2026/09/26 19:16	tool	grepper	0m Args: { "Expression": "table", "PathPrefix": "kernel/bpf/cgroup.c" } Results: { "Output": "kernel/bpf/cgroup.c=1115=static struct bpf_prog_list find_detach_entry(struct hlist_head progs,\n--\nkernel/bpf/cgroup.c-1148- * purge_effective_progs() - After compute_effective_progs fails to alloc new\nkernel/bpf/cgroup.c:1149: * cgrp-\u003ebpf.inactive table we can recover by\nkernel/bpf/cgroup.c-1150- * recomputing the array in place.\n--\nkernel/bpf/cgroup.c=1585=int cgroup_bpf_prog_query(const union bpf_attr attr,\n--\nkernel/bpf/cgroup.c-1609- \nkernel/bpf/cgroup.c:1610: * The program type passed in via @type must be suitable for network\nkernel/bpf/cgroup.c-1611- * filtering. No further check is performed to assert that.\n--\nkernel/bpf/cgroup.c=1687=EXPORT_SYMBOL(__cgroup_bpf_run_filter_skb);\n--\nkernel/bpf/cgroup.c-1695- \nkernel/bpf/cgroup.c:1696: The program type passed in via @type must be suitable for sock\nkernel/bpf/cgroup.c-1697- * filtering. No further check is performed to assert that.\n--\nkernel/bpf/cgroup.c=1766=EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_addr);\n--\nkernel/bpf/cgroup.c-1777- \nkernel/bpf/cgroup.c:1778: The program type passed in via @type must be suitable for sock_ops\nkernel/bpf/cgroup.c-1779- * filtering. No further check is performed to assert that.\n--\nkernel/bpf/cgroup.c=1926=const struct bpf_verifier_ops cg_dev_verifier_ops = {\n--\nkernel/bpf/cgroup.c-1933- \nkernel/bpf/cgroup.c:1934: @head: sysctl table header\nkernel/bpf/cgroup.c:1935: * @table: sysctl table\nkernel/bpf/cgroup.c-1936- * @write: sysctl is being read (= 0) or written (= 1)\n--\nkernel/bpf/cgroup.c-1951- /\nkernel/bpf/cgroup.c:1952:int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header head,\nkernel/bpf/cgroup.c:1953:\t\t\t\t const struct ctl_table table, int write,\nkernel/bpf/cgroup.c-1954-\t\t\t\t char buf, size_t pcount, loff_t ppos,\n--\nkernel/bpf/cgroup.c-1958-\t\t.head = head,\nkernel/bpf/cgroup.c:1959:\t\t.table = table,\nkernel/bpf/cgroup.c-1960-\t\t.write = write,\n--\nkernel/bpf/cgroup.c-1973-\tif (!ctx.cur_val \|\|\nkernel/bpf/cgroup.c:1974:\t table-\u003eproc_handler(table, 0, ctx.cur_val, \u0026ctx.cur_len, \u0026pos)) {\nkernel/bpf/cgroup.c-1975-\t\t/ Let BPF program decide how to proceed. /\n--\nkernel/bpf/cgroup.c=2275=static ssize_t sysctl_cpy_dir(const struct ctl_dir dir, char *bufp,\n--\nkernel/bpf/cgroup.c-2285-\nkernel/bpf/cgroup.c:2286:\tret = strscpy(bufp, dir-\u003eheader.ctl_table[0].procname, lenp);\nkernel/bpf/cgroup.c-2287-\tif (ret \u003c 0)\n--\nkernel/bpf/cgroup.c=2306=BPF_CALL_4(bpf_sysctl_get_name, struct bpf_sysctl_kern , ctx, char *, buf,\n--\nkernel/bpf/cgroup.c-2321-\nkernel/bpf/cgroup.c:2322:\tret = strscpy(buf, ctx-\u003etable-\u003eprocname, buf_len);\nkernel/bpf/cgroup.c-2323-\n" }
77/3	2026/09/26 19:16	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36711 output: 35 thoughts: 1437 Thoughts: Analyzing BPF Sysctl Access and Potential Vulnerabilities Okay, so I'm looking at how the BPF sysctl interacts with the system. It appears the flow is pretty straightforward: it uses `ctx->table->procname` and calls `ctx->table->proc_handler`. The `proc_handler` seems to be the core, handling various sysctl types like integer vectors, min/max values, and IPC-related parameters. I can see these handlers read values from `table->data`, `table->maxlen`, `table->extra1`, and `table->extra2`. For reading sysctl values, they grab the data from `table->data`, format it into a buffer `kbuf`, and then copy the data to user space via `copy_to_iter`. The buffer `kbuf` is dynamically allocated using `kvzalloc`. My initial concern was around `buf->data` potentially pointing to invalid memory or leading to out-of-bounds reads. So, I dug into `sysctl_apply_ctx`. This function's purpose is to resolve the correct `ctl_table` entry. It calculates an offset to get the correct data pointer, and, as I read through it, I can see how it works. Essentially, `off` is calculated as the offset of the data field within the `ipc_namespace` structure (or whatever structure is relevant to the specific sysctl). It's using the difference between a template ( `head->ctx.tmpl` which seems to be initialized with the `init_ipc_ns` instance) and an instance (`head->ctx.inst`, which is the actual namespace `ns` in use). `entry->data` is initialized to the address of a field in `init_ipc_ns`. So, the calculation gives the correct pointer to the instance field, matching the original manual pointer adjustment. This makes sense; it's a clean and safer way to handle this. It matches the manual pointer adjustments previously in place. I also see that the `ctl_table` itself is now not duplicated. Previously, `setup_ipc_sysctls` used `kmemdup` to allocate a copy of `ipc_sysctls`, and `retire_ipc_sysctls` would free this duplicate. This is no longer the case. The `ctl_table` (like `ipc_sysctls`) is a `static const` structure, now, and the `kfree` call has been removed from the `retire_` functions. Further, it seems the code now also removes the use of `ctl_table_arg` in `retire_ipc_sysctls`! This makes the code cleaner, and avoids any double-free issues if the dynamic allocation was somehow missed.
78/3	2026/09/26 19:16	tool	grepper	0m Args: { "Expression": "ctl_table_arg", "PathPrefix": "fs/proc/proc_sysctl.c" } Results: { "Output": "fs/proc/proc_sysctl.c=77=static struct ctl_table_root sysctl_table_root = {\n--\nfs/proc/proc_sysctl.c-81-\t\t .ctl_table = root_table }},\nfs/proc/proc_sysctl.c:82:\t\t.ctl_table_arg = root_table,\nfs/proc/proc_sysctl.c-83-\t\t.root = \u0026sysctl_table_root,\n--\nfs/proc/proc_sysctl.c=192=static void init_header(struct ctl_table_header *head,\n--\nfs/proc/proc_sysctl.c-197-\thead-\u003ectl_table_size = table_size;\nfs/proc/proc_sysctl.c:198:\thead-\u003ectl_table_arg = table;\nfs/proc/proc_sysctl.c-199-\thead-\u003eused = 0;\n" }
79/3	2026/09/26 19:16	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 39012 output: 19 thoughts: 18 Thoughts: Okay, here's my summary, tailored for an expert audience, as if I'm thinking these things myself: Diving into `ctl_table_arg` Usage Alright, time to get my hands dirty. I need to understand the landscape of `ctl_table_arg` within the kernel. I'm thinking, this isn't just a casual perusal; I want a comprehensive overview of every usage. Forget skimming – I'm talking a deep dive to identify patterns, potential areas for optimization, and, quite frankly, any potential vulnerabilities. I need to know the context of each instance: where is it being used? What type of control structures are being passed, and are we dealing with sysctls, procfs, or something else entirely? The type safety and potential for type mismatches are always a consideration when digging into these low-level interfaces. I'll need to look at how data is marshaled, validated, and how potential errors are handled. I'm expecting some interesting edge cases to pop up, so a systematic approach is key. Let's start digging!
80/3	2026/09/26 19:16	tool	grepper	0m Args: { "Expression": "ctl_table_arg" } Results: { "Output": "drivers/net/vrf.c=1888=static void vrf_netns_exit_sysctl(struct net net)\n--\ndrivers/net/vrf.c-1892-\ndrivers/net/vrf.c:1893:\ttable = nn_vrf-\u003ectl_hdr-\u003ectl_table_arg;\ndrivers/net/vrf.c-1894-\tunregister_net_sysctl_table(nn_vrf-\u003ectl_hdr);\n--\nfs/proc/proc_sysctl.c=77=static struct ctl_table_root sysctl_table_root = {\n--\nfs/proc/proc_sysctl.c-81-\t\t .ctl_table = root_table }},\nfs/proc/proc_sysctl.c:82:\t\t.ctl_table_arg = root_table,\nfs/proc/proc_sysctl.c-83-\t\t.root = \u0026sysctl_table_root,\n--\nfs/proc/proc_sysctl.c=192=static void init_header(struct ctl_table_header head,\n--\nfs/proc/proc_sysctl.c-197-\thead-\u003ectl_table_size = table_size;\nfs/proc/proc_sysctl.c:198:\thead-\u003ectl_table_arg = table;\nfs/proc/proc_sysctl.c-199-\thead-\u003eused = 0;\n--\ninclude/linux/sysctl.h=294=struct ctl_table_header {\n--\ninclude/linux/sysctl.h-305-\tstruct completion unregistering;\ninclude/linux/sysctl.h:306:\tconst struct ctl_table ctl_table_arg;\ninclude/linux/sysctl.h-307-\tstruct ctl_table_root root;\n--\nkernel/pid.c=807=void unregister_pidns_sysctls(struct pid_namespace pidns)\n--\nkernel/pid.c-811-\nkernel/pid.c:812:\ttbl = pidns-\u003esysctls-\u003ectl_table_arg;\nkernel/pid.c-813-\tunregister_sysctl_table(pidns-\u003esysctls);\n--\nkernel/ucount.c=124=void retire_userns_sysctls(struct user_namespace ns)\n--\nkernel/ucount.c-128-\nkernel/ucount.c:129:\ttbl = ns-\u003esysctls-\u003ectl_table_arg;\nkernel/ucount.c-130-\tunregister_sysctl_table(ns-\u003esysctls);\n--\nnet/bridge/br_netfilter_hooks.c=1266=static void br_netfilter_sysctl_exit_net(struct net net,\n--\nnet/bridge/br_netfilter_hooks.c-1268-{\nnet/bridge/br_netfilter_hooks.c:1269:\tconst struct ctl_table table = brnet-\u003ectl_hdr-\u003ectl_table_arg;\nnet/bridge/br_netfilter_hooks.c-1270-\n--\nnet/core/sysctl_net_core.c=837=static __net_exit void sysctl_core_net_exit(struct net net)\n--\nnet/core/sysctl_net_core.c-840-\nnet/core/sysctl_net_core.c:841:\ttbl = net-\u003ecore.sysctl_hdr-\u003ectl_table_arg;\nnet/core/sysctl_net_core.c-842-\tunregister_net_sysctl_table(net-\u003ecore.sysctl_hdr);\n--\nnet/ieee802154/6lowpan/reassembly.c=403=static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net net)\n--\nnet/ieee802154/6lowpan/reassembly.c-408-\nnet/ieee802154/6lowpan/reassembly.c:409:\ttable = ieee802154_lowpan-\u003esysctl.frags_hdr-\u003ectl_table_arg;\nnet/ieee802154/6lowpan/reassembly.c-410-\tunregister_net_sysctl_table(ieee802154_lowpan-\u003esysctl.frags_hdr);\n--\nnet/ipv4/devinet.c=2916=static __net_exit void devinet_exit_net(struct net net)\n--\nnet/ipv4/devinet.c-2924-#ifdef CONFIG_SYSCTL\nnet/ipv4/devinet.c:2925:\ttbl = net-\u003eipv4.forw_hdr-\u003ectl_table_arg;\nnet/ipv4/devinet.c-2926-\tunregister_net_sysctl_table(net-\u003eipv4.forw_hdr);\n--\nnet/ipv4/ip_fragment.c=622=static void __net_exit ip4_frags_ns_ctl_unregister(struct net net)\n--\nnet/ipv4/ip_fragment.c-625-\nnet/ipv4/ip_fragment.c:626:\ttable = net-\u003eipv4.frags_hdr-\u003ectl_table_arg;\nnet/ipv4/ip_fragment.c-627-\tunregister_net_sysctl_table(net-\u003eipv4.frags_hdr);\n--\nnet/ipv4/route.c=3676=static __net_exit void sysctl_route_net_exit(struct net net)\n--\nnet/ipv4/route.c-3679-\nnet/ipv4/route.c:3680:\ttbl = net-\u003eipv4.route_hdr-\u003ectl_table_arg;\nnet/ipv4/route.c-3681-\tunregister_net_sysctl_table(net-\u003eipv4.route_hdr);\n--\nnet/ipv4/sysctl_net_ipv4.c=1722=static __net_exit void ipv4_sysctl_exit_net(struct net net)\n--\nnet/ipv4/sysctl_net_ipv4.c-1725-\nnet/ipv4/sysctl_net_ipv4.c:1726:\ttable = net-\u003eipv4.ipv4_hdr-\u003ectl_table_arg;\nnet/ipv4/sysctl_net_ipv4.c-1727-\tunregister_net_sysctl_table(net-\u003eipv4.ipv4_hdr);\n--\nnet/ipv4/xfrm4_policy.c=195=static __net_exit void xfrm4_net_sysctl_exit(struct net net)\n--\nnet/ipv4/xfrm4_policy.c-201-\nnet/ipv4/xfrm4_policy.c:202:\ttable = net-\u003eipv4.xfrm4_hdr-\u003ectl_table_arg;\nnet/ipv4/xfrm4_policy.c-203-\tunregister_net_sysctl_table(net-\u003eipv4.xfrm4_hdr);\n--\nnet/ipv6/addrconf.c=7373=static void __addrconf_sysctl_unregister(struct net net,\n--\nnet/ipv6/addrconf.c-7380-\nnet/ipv6/addrconf.c:7381:\ttable = p-\u003esysctl_header-\u003ectl_table_arg;\nnet/ipv6/addrconf.c-7382-\tunregister_net_sysctl_table(p-\u003esysctl_header);\n--\nnet/ipv6/netfilter/nf_conntrack_reasm.c=104=static void __net_exit nf_ct_frags6_sysctl_unregister(struct net net)\n--\nnet/ipv6/netfilter/nf_conntrack_reasm.c-108-\nnet/ipv6/netfilter/nf_conntrack_reasm.c:109:\ttable = nf_frag-\u003enf_frag_frags_hdr-\u003ectl_table_arg;\nnet/ipv6/netfilter/nf_conntrack_reasm.c-110-\tunregister_net_sysctl_table(nf_frag-\u003enf_frag_frags_hdr);\n--\nnet/ipv6/reassembly.c=489=static void __net_exit ip6_frags_ns_sysctl_unregister(struct net net)\n--\nnet/ipv6/reassembly.c-492-\nnet/ipv6/reassembly.c:493:\ttable = net-\u003eipv6.sysctl.frags_hdr-\u003ectl_table_arg;\nnet/ipv6/reassembly.c-494-\tunregister_net_sysctl_table(net-\u003eipv6.sysctl.frags_hdr);\n--\nnet/ipv6/sysctl_net_ipv6.c=312=static void __net_exit ipv6_sysctl_net_exit(struct net net)\n--\nnet/ipv6/sysctl_net_ipv6.c-317-\nnet/ipv6/sysctl_net_ipv6.c:318:\tipv6_table = net-\u003eipv6.sysctl.hdr-\u003ectl_table_arg;\nnet/ipv6/sysctl_net_ipv6.c:319:\tipv6_route_table = net-\u003eipv6.sysctl.route_hdr-\u003ectl_table_arg;\nnet/ipv6/sysctl_net_ipv6.c:320:\tipv6_icmp_table = net-\u003eipv6.sysctl.icmp_hdr-\u003ectl_table_arg;\nnet/ipv6/sysctl_net_ipv6.c-321-\n--\nnet/ipv6/xfrm6_policy.c=241=static void __net_exit xfrm6_net_sysctl_exit(struct net net)\n--\nnet/ipv6/xfrm6_policy.c-247-\nnet/ipv6/xfrm6_policy.c:248:\ttable = net-\u003eipv6.sysctl.xfrm6_hdr-\u003ectl_table_arg;\nnet/ipv6/xfrm6_policy.c-249-\tunregister_net_sysctl_table(net-\u003eipv6.sysctl.xfrm6_hdr);\n--\nnet/mpls/af_mpls.c=1467=static void mpls_dev_sysctl_unregister(struct net_device dev,\n--\nnet/mpls/af_mpls.c-1475-\nnet/mpls/af_mpls.c:1476:\ttable = mdev-\u003esysctl-\u003ectl_table_arg;\nnet/mpls/af_mpls.c-1477-\tunregister_net_sysctl_table(mdev-\u003esysctl);\n--\nnet/mpls/af_mpls.c=2779=static __net_exit void mpls_net_exit(struct net net)\n--\nnet/mpls/af_mpls.c-2785-\nnet/mpls/af_mpls.c:2786:\ttable = net-\u003empls.ctl-\u003ectl_table_arg;\nnet/mpls/af_mpls.c-2787-\tunregister_net_sysctl_table(net-\u003empls.ctl);\n--\nnet/mptcp/ctrl.c=425=static void mptcp_pernet_del_table(struct mptcp_pernet pernet)\nnet/mptcp/ctrl.c-426-{\nnet/mptcp/ctrl.c:427:\tconst struct ctl_table table = pernet-\u003ectl_table_hdr-\u003ectl_table_arg;\nnet/mptcp/ctrl.c-428-\n--\nnet/netfilter/nf_conntrack_standalone.c=1059=static void nf_conntrack_standalone_fini_sysctl(struct net net)\n--\nnet/netfilter/nf_conntrack_standalone.c-1063-\nnet/netfilter/nf_conntrack_standalone.c:1064:\ttable = cnet-\u003esysctl_header-\u003ectl_table_arg;\nnet/netfilter/nf_conntrack_standalone.c-1065-\tunregister_net_sysctl_table(cnet-\u003esysctl_header);\n--\nnet/netfilter/nf_hooks_lwtunnel.c=96=static void __net_exit nf_lwtunnel_net_exit(struct net net)\n--\nnet/netfilter/nf_hooks_lwtunnel.c-99-\nnet/netfilter/nf_hooks_lwtunnel.c:100:\ttable = net-\u003enf.nf_lwtnl_dir_header-\u003ectl_table_arg;\nnet/netfilter/nf_hooks_lwtunnel.c-101-\tunregister_net_sysctl_table(net-\u003enf.nf_lwtnl_dir_header);\n--\nnet/netfilter/nf_log.c=540=static void netfilter_log_sysctl_exit(struct net net)\n--\nnet/netfilter/nf_log.c-543-\nnet/netfilter/nf_log.c:544:\ttable = net-\u003enf.nf_log_dir_header-\u003ectl_table_arg;\nnet/netfilter/nf_log.c-545-\tunregister_net_sysctl_table(net-\u003enf.nf_log_dir_header);\n--\nnet/sctp/sysctl.c=616=void sctp_sysctl_net_unregister(struct net net)\n--\nnet/sctp/sysctl.c-623-\nnet/sctp/sysctl.c:624:\ttable = header-\u003ectl_table_arg;\nnet/sctp/sysctl.c-625-\tunregister_net_sysctl_table(header);\n--\nnet/smc/smc_sysctl.c=266=void __net_exit smc_sysctl_net_exit(struct net net)\n--\nnet/smc/smc_sysctl.c-269-\nnet/smc/smc_sysctl.c:270:\ttable = net-\u003esmc.smc_hdr-\u003ectl_table_arg;\nnet/smc/smc_sysctl.c-271-\tunregister_net_sysctl_table(net-\u003esmc.smc_hdr);\n--\nnet/unix/sysctl_net_unix.c=65=void unix_sysctl_unregister(struct net net)\n--\nnet/unix/sysctl_net_unix.c-68-\nnet/unix/sysctl_net_unix.c:69:\ttable = net-\u003eunx.ctl-\u003ectl_table_arg;\nnet/unix/sysctl_net_unix.c-70-\tunregister_net_sysctl_table(net-\u003eunx.ctl);\n--\nnet/vmw_vsock/af_vsock.c=2979=static void vsock_sysctl_unregister(struct net net)\n--\nnet/vmw_vsock/af_vsock.c-2982-\nnet/vmw_vsock/af_vsock.c:2983:\ttable = net-\u003evsock.sysctl_hdr-\u003ectl_table_arg;\nnet/vmw_vsock/af_vsock.c-2984-\tunregister_net_sysctl_table(net-\u003evsock.sysctl_hdr);\n--\nnet/xfrm/xfrm_sysctl.c=74=void __net_exit xfrm_sysctl_fini(struct net *net)\n--\nnet/xfrm/xfrm_sysctl.c-77-\nnet/xfrm/xfrm_sysctl.c:78:\ttable = net-\u003exfrm.sysctl_hdr-\u003ectl_table_arg;\nnet/xfrm/xfrm_sysctl.c-79-\tunregister_net_sysctl_table(net-\u003exfrm.sysctl_hdr);\n" }
81/3	2026/09/26 19:16	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43247 output: 479 thoughts: 2345 Thoughts: KMSAN Assessment: sysctl Table Optimization Alright, let's break this down. We've optimized the handling of sysctl tables for IPC and MQ namespaces. Previously, these tables were duplicated using `kmemdup`, but now we're passing static tables directly, avoiding the overhead of dynamic allocation and freeing. My objective here is to determine if this change introduces any risk of uninitialized memory usage, particularly risks that would only be caught by KMSAN. Since KMSAN is an extremely expensive tool to run, I need to make sure it's absolutely necessary. I went through the checklist to see if the patch introduced changes that would potentially expose uninitialized memory. 1. User-Space Exposure: I checked, and there are no kernel structures that are sent to user space that could contain uninitialized fields. Sysctl read operations format the data correctly, into kernel allocated buffers that are initialized with `kvzalloc` before being copied to userspace using `copy_to_iter`. The `ctl_table` structures are purely internal to the kernel, so no risk there. 2. Conditional Logic: Then, I examined the logic surrounding the `struct ctl_table ctx_entry`, which is a local variable. I tracked its usage through `proc_sys_call_handler` and `proc_sys_permission`, and into `sysctl_apply_ctx`. The critical point is whether this variable is read before it's written to. It turns out that `sysctl_apply_ctx` uses a static `ctl_table`, and always initializes the local `ctx_entry` with a copy of a static `ctl_table` before the updated `buf` is returned, so there's no way that `ctx_entry` could be used with uninitialized fields. There's also the `head->ctx` to consider; that's initialized by either explicit construction, or `kzalloc`. The initializers are correct. 3. Data Structure Initialization: I checked for allocation of complex data structures where uninitialized fields could be read, and I found none. 4. Bounds Checks/Uninitialized Bytes: The potential for a `off` offset calculation in `sysctl_apply_ctx` causing issues arose. If the `entry->data` pointer was not within the allocated memory, the offset could go out-of-bounds, potentially leading to a memory access error. I realized that this would be caught by KASAN because it would be out-of-bounds memory access! Also, the underlying `struct ipc_namespace` is zero-initialized via `kzalloc_obj`, and the offset calculation is strictly within the allocated memory for that structure. I double-checked all the occurrences of the `CTL_TABLE_F_CTX_DATA` flag and that all the table checks are performed on registration. Conclusion: After a careful review, the answer is no. This patch does not introduce any risks of uninitialized memory that would be detected only by KMSAN. Standard bug detectors like KASAN are sufficient here. So, I can set `NeedsKMSAN = false`. I also took the time to write a succinct summary of the changes and the reasoning, contrasting KASAN versus KMSAN for clarity. This is a good, low-risk optimization. Now let's call the `set-results` tool and move on.
82/3	2026/09/26 19:16	tool	set-results	0m Args: { "KMSANReasoning": "The patch refactors per-namespace sysctl tables in IPC and POSIX message queues (mq) to eliminate dynamic kmemdup allocations. Instead, it introduces `struct sysctl_context` and a flag `CTL_TABLE_F_CTX_DATA` to resolve per-namespace struct member offsets dynamically via `sysctl_apply_ctx()` into a local stack buffer (`ctx_entry`).\n\nKMSAN vs KASAN applicability analysis:\n1. Uninitialized memory reads / branching:\n - The stack variables `struct ctl_table ctx_entry` in `proc_sys_call_handler()` and `proc_sys_permission()` are passed as out-parameters to `sysctl_apply_ctx()`. When `CTL_TABLE_F_CTX_DATA` is set, `buf = entry;` fully initializes the struct from the static const sysctl table before updating `buf-\u003edata` and returning `buf`. When the flag is not set, `sysctl_apply_ctx()` returns `entry` directly, leaving `buf` untouched and completely unreferenced.\n - The `struct sysctl_context` created by `SYSCTL_CTX` initializes all struct fields (`inst` and `tmpl`) via a compound literal.\n - `struct ctl_table_header` is allocated using `kzalloc()`, and `struct ipc_namespace` is allocated using `kzalloc_obj()`.\n2. Kernel-to-userspace info-leaks:\n - `struct ctl_table` is an internal kernel structure and is never copied to user space. Data written to userspace by sysctl read handlers is formatted into `kbuf` allocated with `kvzalloc()`.\n3. Memory safety risks:\n - Any potential offset calculation errors (`(char )head-\u003ectx.inst + off`) would lead to out-of-bounds pointer dereferences, which are detected by KASAN, not KMSAN.\n\nTherefore, the patch does not expose any uninitialized memory risks or info-leaks. A dedicated KMSAN fuzzing session is not warranted; standard KASAN fuzzing is sufficient.", "NeedsKMSAN": false } Results:* { "KMSANReasoning": "The patch refactors per-namespace sysctl tables in IPC and POSIX message queues (mq) to eliminate dynamic kmemdup allocations. Instead, it introduces `struct sysctl_context` and a flag `CTL_TABLE_F_CTX_DATA` to resolve per-namespace struct member offsets dynamically via `sysctl_apply_ctx()` into a local stack buffer (`ctx_entry`).\n\nKMSAN vs KASAN applicability analysis:\n1. Uninitialized memory reads / branching:\n - The stack variables `struct ctl_table ctx_entry` in `proc_sys_call_handler()` and `proc_sys_permission()` are passed as out-parameters to `sysctl_apply_ctx()`. When `CTL_TABLE_F_CTX_DATA` is set, `buf = entry;` fully initializes the struct from the static const sysctl table before updating `buf-\u003edata` and returning `buf`. When the flag is not set, `sysctl_apply_ctx()` returns `entry` directly, leaving `buf` untouched and completely unreferenced.\n - The `struct sysctl_context` created by `SYSCTL_CTX` initializes all struct fields (`inst` and `tmpl`) via a compound literal.\n - `struct ctl_table_header` is allocated using `kzalloc()`, and `struct ipc_namespace` is allocated using `kzalloc_obj()`.\n2. Kernel-to-userspace info-leaks:\n - `struct ctl_table` is an internal kernel structure and is never copied to user space. Data written to userspace by sysctl read handlers is formatted into `kbuf` allocated with `kvzalloc()`.\n3. Memory safety risks:\n - Any potential offset calculation errors (`(char *)head-\u003ectx.inst + off`) would lead to out-of-bounds pointer dereferences, which are detected by KASAN, not KMSAN.\n\nTherefore, the patch does not expose any uninitialized memory risks or info-leaks. A dedicated KMSAN fuzzing session is not warranted; standard KASAN fuzzing is sufficient.", "NeedsKMSAN": false }

LLM Calls Summary:
Total Calls	Total Tokens	Avg Tokens	Total Duration (Seconds)	Avg Duration (Seconds)

Tool Calls Summary:
Total Calls	Total Duration (Seconds)	Avg Duration (Seconds)