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Seq	Timestamp	Type	Name	Duration
0/0	2026/10/26 20:23	flow	patch-triage	2m Args: null Results: { "EnableConfigs": [ "NVME_TARGET", "BLK_CGROUP", "NVME_TARGET_LOOP", "CONFIGFS_FS" ], "FocusSymbols": [ "nvmet_ns_cgroup_id_store", "nvmet_blkcg_ns_enable", "nvmet_blkcg_ns_disable", "nvmet_blkcg_begin", "nvmet_blkcg_end", "nvmet_blkcg_work", "nvmet_ns_enable" ], "KMSANReasoning": "The patch adds cgroup-based I/O throttling support to NVMe target (nvmet) namespaces via configfs (`cgroup_id` attribute), dispatching I/O requests through dedicated per-namespace workqueues associated with the corresponding blkcg.\n\nFrom a memory safety perspective:\n1. All newly introduced struct members in `struct nvmet_ns` (`cgroup_id`, `cgrp`, `blkcg_wq`) are zero-initialized at allocation time via `kzalloc_obj()` in `nvmet_ns_alloc()`.\n2. The new configfs attribute show handler (`nvmet_ns_cgroup_id_show`) formats a scalar `u64` into an ASCII string using `snprintf()`, presenting no uninitialized padding or info-leak risk.\n3. In `nvmet_req`, the new fields (`blkcg_execute`, `blkcg_work`) are initialized via `INIT_WORK` and direct assignment during request handling when `ns-\u003ecgrp` is active, and local variables (`associated`, `status`, `noio_flag`) are explicitly assigned before use.\n4. Any potential issues with this patch relate to concurrency, lifetime management of the workqueue/cgroup reference across disable/enable operations, use-after-free, or locking dependencies, all of which are covered by KASAN and LOCKDEP.\n\nThere are no uninitialized memory reads or kernel info-leaks, so a dedicated KMSAN session is not warranted.", "NeedsKMSAN": false, "Reasoning": "The patch introduces cgroup v2 throttling and charging support for NVMe target (nvmet) namespaces. When a namespace is configured with a cgroup_id via configfs, I/O commands are dispatched through a dedicated per-namespace workqueue and associated with the cgroup's blkcg css via kthread_associate_blkcg. This code is fully reachable in standard virtualized QEMU environments using virtual/loopback transports (such as nvme-loop or nvmet-tcp over loopback). The changes add concurrency, asynchronous workqueue handling, cgroup refcounting, and teardown synchronization, which warrants fuzzing to detect potential race conditions or resource leaks.", "WorthFuzzing": true }
1/1	2026/10/26 20:23	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 21158167c09894da68b4c04b907acbadceeeed2a\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Mon Oct 26 20:23:56 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/Documentation/ABI/stable/configfs-nvmet b/Documentation/ABI/stable/configfs-nvmet\nindex 36b587404ee7ef..ea9c4083c6a0de 100644\n--- a/Documentation/ABI/stable/configfs-nvmet\n+++ b/Documentation/ABI/stable/configfs-nvmet\n@@ -314,6 +314,22 @@ Description:\n \t\tattr_subsys_vendor_id: Shows or sets the PCI subsystem\n \t\tvendor ID. Displayed in \"0x%x\" format.\n \n+What:\t\t/config/nvmet/subsystems/NAME/namespaces/NSID/cgroup_id\n+Date:\t\tOctober 2026\n+KernelVersion:\t7.5\n+Contact:\tPeng Yu \u003cyupeng0921@gmail.com\u003e\n+Description:\n+\t\tShows or sets the cgroup2 ID of the cgroup to charge this\n+\t\tnamespace's I/O to. Writing 0 clears it. The I/O is\n+\t\tcharged to the cgroup's effective io css: the cgroup\n+\t\titself or its nearest ancestor with the io controller\n+\t\tenabled. The namespace must be disabled before\n+\t\tmodification. Enabling the namespace fails if the cgroup\n+\t\tcan't be found or if buffered_io is set. A cgroup that is\n+\t\tremoved and created again gets a new ID.\n+\n+\t\tOnly available when CONFIG_BLK_CGROUP is enabled.\n+\n What:\t\t/config/nvmet/hosts/HOSTNQN/dhchap_key\n What:\t\t/config/nvmet/hosts/HOSTNQN/dhchap_ctrl_key\n What:\t\t/config/nvmet/hosts/HOSTNQN/dhchap_hash\ndiff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c\nindex 8aea64d279c4af..9f0d48677c4a22 100644\n--- a/drivers/nvme/target/configfs.c\n+++ b/drivers/nvme/target/configfs.c\n@@ -564,6 +564,50 @@ static ssize_t nvmet_ns_device_path_store(struct config_item item,\n \n CONFIGFS_ATTR(nvmet_ns_, device_path);\n \n+#ifdef CONFIG_BLK_CGROUP\n+static ssize_t nvmet_ns_cgroup_id_show(struct config_item item, char page)\n+{\n+\tstruct nvmet_ns ns = to_nvmet_ns(item);\n+\tstruct nvmet_subsys subsys = ns-\u003esubsys;\n+\tssize_t ret;\n+\n+\tmutex_lock(\u0026subsys-\u003elock);\n+\tret = snprintf(page, PAGE_SIZE, \"%llu\\n\", ns-\u003ecgroup_id);\n+\tmutex_unlock(\u0026subsys-\u003elock);\n+\treturn ret;\n+}\n+\n+static ssize_t nvmet_ns_cgroup_id_store(struct config_item item,\n+\t\tconst char page, size_t count)\n+{\n+\tstruct nvmet_ns ns = to_nvmet_ns(item);\n+\tstruct nvmet_subsys subsys = ns-\u003esubsys;\n+\tu64 cgroup_id;\n+\tint ret;\n+\n+\tret = kstrtou64(page, 0, \u0026cgroup_id);\n+\tif (ret)\n+\t\treturn ret;\n+\n+\tmutex_lock(\u0026subsys-\u003elock);\n+\n+\tif (ns-\u003eenabled) {\n+\t\tret = -EBUSY;\n+\t\tgoto out_unlock;\n+\t}\n+\n+\t/ Writing 0 clears the association. /\n+\tns-\u003ecgroup_id = cgroup_id;\n+\tret = count;\n+\n+out_unlock:\n+\tmutex_unlock(\u0026subsys-\u003elock);\n+\treturn ret;\n+}\n+\n+CONFIGFS_ATTR(nvmet_ns_, cgroup_id);\n+#endif / CONFIG_BLK_CGROUP /\n+\n #ifdef CONFIG_PCI_P2PDMA\n static ssize_t nvmet_ns_p2pmem_show(struct config_item item, char page)\n {\n@@ -836,6 +880,9 @@ static struct configfs_attribute nvmet_ns_attrs[] = {\n \t\u0026nvmet_ns_attr_buffered_io,\n \t\u0026nvmet_ns_attr_revalidate_size,\n \t\u0026nvmet_ns_attr_resv_enable,\n+#ifdef CONFIG_BLK_CGROUP\n+\t\u0026nvmet_ns_attr_cgroup_id,\n+#endif\n #ifdef CONFIG_PCI_P2PDMA\n \t\u0026nvmet_ns_attr_p2pmem,\n #endif\ndiff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c\nindex 8353950f346f3c..5472a8b3853ca8 100644\n--- a/drivers/nvme/target/core.c\n+++ b/drivers/nvme/target/core.c\n@@ -4,12 +4,15 @@\n * Copyright (c) 2015-2016 HGST, a Western Digital Company.\n /\n #define pr_fmt(fmt) KBUILD_MODNAME \": \" fmt\n+#include \u003clinux/cgroup.h\u003e\n #include \u003clinux/hex.h\u003e\n+#include \u003clinux/kthread.h\u003e\n #include \u003clinux/module.h\u003e\n #include \u003clinux/random.h\u003e\n #include \u003clinux/rculist.h\u003e\n #include \u003clinux/pci-p2pdma.h\u003e\n #include \u003clinux/scatterlist.h\u003e\n+#include \u003clinux/sched/mm.h\u003e\n \n #include \u003cgenerated/utsrelease.h\u003e\n \n@@ -481,8 +484,144 @@ void nvmet_put_namespace(struct nvmet_ns ns)\n \tpercpu_ref_put(\u0026ns-\u003eref);\n }\n \n+#ifdef CONFIG_BLK_CGROUP\n+static int nvmet_blkcg_ns_enable(struct nvmet_ns ns)\n+{\n+\tstruct cgroup cgrp;\n+\n+\tif (!ns-\u003ecgroup_id)\n+\t\treturn 0;\n+\n+\t/\n+\t Buffered writes will be handled by a separate thread,\n+\t * these IOs have no namespace/cgroup information at that time,\n+\t * so we don't support buffered io.\n+\t /\n+\tif (ns-\u003ebuffered_io) {\n+\t\tpr_err(\"cgroup_id is not supported with buffered_io: %s\\n\",\n+\t\t ns-\u003edevice_path);\n+\t\treturn -EINVAL;\n+\t}\n+\n+\tcgrp = cgroup_get_from_id(ns-\u003ecgroup_id);\n+\tif (IS_ERR(cgrp)) {\n+\t\tpr_err(\"failed to resolve cgroup id %llu: %ld\\n\",\n+\t\t ns-\u003ecgroup_id, PTR_ERR(cgrp));\n+\t\treturn PTR_ERR(cgrp);\n+\t}\n+\n+\tns-\u003eblkcg_wq = alloc_workqueue(\"nvmet-blkcg-%u\",\n+\t\t\tWQ_MEM_RECLAIM \| WQ_UNBOUND, num_online_cpus(),\n+\t\t\tns-\u003ensid);\n+\tif (!ns-\u003eblkcg_wq) {\n+\t\tcgroup_put(cgrp);\n+\t\treturn -ENOMEM;\n+\t}\n+\n+\tns-\u003ecgrp = cgrp;\n+\treturn 0;\n+}\n+\n+static void nvmet_blkcg_ns_disable(struct nvmet_ns ns)\n+{\n+\tif (ns-\u003ecgrp) {\n+\t\t/\n+\t\t No command is left, but the work item of a command that\n+\t\t * completed from inside -\u003eblkcg_execute() may still be\n+\t\t * returning: destroy_workqueue() waits for it.\n+\t\t /\n+\t\tdestroy_workqueue(ns-\u003eblkcg_wq);\n+\t\tns-\u003eblkcg_wq = NULL;\n+\t\tcgroup_put(ns-\u003ecgrp);\n+\t\tns-\u003ecgrp = NULL;\n+\t}\n+}\n+\n+/\n+ * Charge the I/O that the current work item submits for @req to the\n+ * effective io css of the namespace's cgroup, looked up for each command.\n+ /\n+bool nvmet_blkcg_begin(struct nvmet_req req)\n+{\n+\tstruct nvmet_ns ns = req-\u003ens;\n+\tstruct cgroup_subsys_state css;\n+\n+\t/* a disable waits for the command: don't throttle it any more /\n+\tif (!ns-\u003ecgrp \|\| !READ_ONCE(ns-\u003eenabled))\n+\t\treturn false;\n+\n+\tcss = cgroup_get_e_css(ns-\u003ecgrp, \u0026io_cgrp_subsys);\n+\tkthread_associate_blkcg(css);\n+\tcss_put(css);\n+\treturn true;\n+}\n+\n+void nvmet_blkcg_end(bool associated)\n+{\n+\tif (associated)\n+\t\tkthread_associate_blkcg(NULL);\n+}\n+\n+/\n+ * The io.cost and io.latency enforce their limits by putting the thread to\n+ * sleep. A transport thread may be shared by multiple namespaces. In the\n+ * tcp-nvmeof case, all namespaces in the same subsystem may share a\n+ * thread. So we submit the IOs via the workqueue, thus the current thread\n+ * won't be blocked.\n+ /\n+static void nvmet_blkcg_work(struct work_struct work)\n+{\n+\tstruct nvmet_req req =\n+\t\tcontainer_of(work, struct nvmet_req, blkcg_work);\n+\tunsigned int noio_flag;\n+\tbool associated;\n+\n+\t/ its queue is being deleted: abort it rather than throttle it /\n+\tif (unlikely(percpu_ref_is_dying(\u0026req-\u003esq-\u003eref))) {\n+\t\tnvmet_req_complete(req, NVME_SC_ABORT_QUEUE);\n+\t\treturn;\n+\t}\n+\n+\t/ reclaim must not wait for I/O queued on this workqueue /\n+\tnoio_flag = memalloc_noio_save();\n+\tassociated = nvmet_blkcg_begin(req);\n+\treq-\u003eblkcg_execute(req);\n+\tnvmet_blkcg_end(associated);\n+\tmemalloc_noio_restore(noio_flag);\n+}\n+\n+static void nvmet_blkcg_queue_req(struct nvmet_req req)\n+{\n+\tINIT_WORK(\u0026req-\u003eblkcg_work, nvmet_blkcg_work);\n+\tqueue_work(req-\u003ens-\u003eblkcg_wq, \u0026req-\u003eblkcg_work);\n+}\n+\n+static void nvmet_blkcg_init_req(struct nvmet_req req)\n+{\n+\tif (!req-\u003ens-\u003ecgrp)\n+\t\treturn;\n+\n+\treq-\u003eblkcg_execute = req-\u003eexecute;\n+\treq-\u003eexecute = nvmet_blkcg_queue_req;\n+}\n+#else\n+static inline int nvmet_blkcg_ns_enable(struct nvmet_ns ns)\n+{\n+\treturn 0;\n+}\n+\n+static inline void nvmet_blkcg_ns_disable(struct nvmet_ns ns)\n+{\n+}\n+\n+static inline void nvmet_blkcg_init_req(struct nvmet_req req)\n+{\n+}\n+#endif /* CONFIG_BLK_CGROUP /\n+\n static void nvmet_ns_dev_disable(struct nvmet_ns ns)\n {\n+\tnvmet_blkcg_ns_disable(ns);\n \tnvmet_bdev_ns_disable(ns);\n \tnvmet_file_ns_disable(ns);\n }\n@@ -609,6 +748,10 @@ int nvmet_ns_enable(struct nvmet_ns ns)\n \tif (ret)\n \t\tgoto out_unlock;\n \n+\tret = nvmet_blkcg_ns_enable(ns);\n+\tif (ret)\n+\t\tgoto out_dev_disable;\n+\n \tret = nvmet_p2pmem_ns_enable(ns);\n \tif (ret)\n \t\tgoto out_dev_disable;\n@@ -1165,6 +1308,8 @@ static u16 nvmet_parse_io_cmd(struct nvmet_req req)\n \tif (ret)\n \t\treturn ret;\n \n+\tnvmet_blkcg_init_req(req);\n+\n \tif (req-\u003ens-\u003epr.enable) {\n \t\tret = nvmet_pr_check_cmd_access(req);\n \t\tif (ret)\ndiff --git a/drivers/nvme/target/io-cmd-file.c b/drivers/nvme/target/io-cmd-file.c\nindex 695963dd932ee7..673df713c954f9 100644\n--- a/drivers/nvme/target/io-cmd-file.c\n+++ b/drivers/nvme/target/io-cmd-file.c\n@@ -257,8 +257,13 @@ u16 nvmet_file_flush(struct nvmet_req req)\n static void nvmet_file_flush_work(struct work_struct w)\n {\n \tstruct nvmet_req req = container_of(w, struct nvmet_req, f.work);\n+\tbool associated;\n+\tu16 status;\n \n-\tnvmet_req_complete(req, nvmet_file_flush(req));\n+\tassociated = nvmet_blkcg_begin(req);\n+\tstatus = nvmet_file_flush(req);\n+\tnvmet_blkcg_end(associated);\n+\tnvmet_req_complete(req, status);\n }\n \n static void nvmet_file_execute_flush(struct nvmet_req req)\n@@ -266,7 +271,7 @@ static void nvmet_file_execute_flush(struct nvmet_req req)\n \tif (!nvmet_check_transfer_len(req, 0))\n \t\treturn;\n \tINIT_WORK(\u0026req-\u003ef.work, nvmet_file_flush_work);\n-\tqueue_work(nvmet_wq, \u0026req-\u003ef.work);\n+\tnvmet_req_queue_work(req, nvmet_wq, \u0026req-\u003ef.work);\n }\n \n static void nvmet_file_execute_discard(struct nvmet_req req)\n@@ -274,10 +279,12 @@ static void nvmet_file_execute_discard(struct nvmet_req req)\n \tint mode = FALLOC_FL_PUNCH_HOLE \| FALLOC_FL_KEEP_SIZE;\n \tstruct nvme_dsm_range range;\n \tloff_t offset, len;\n+\tbool associated;\n \tu16 status = 0;\n \tint ret;\n \tint i;\n \n+\tassociated = nvmet_blkcg_begin(req);\n \tfor (i = 0; i \u003c= le32_to_cpu(req-\u003ecmd-\u003edsm.nr); i++) {\n \t\tstatus = nvmet_copy_from_sgl(req, i sizeof(range), \u0026range,\n \t\t\t\t\tsizeof(range));\n@@ -300,6 +307,7 @@ static void nvmet_file_execute_discard(struct nvmet_req req)\n \t\t\tbreak;\n \t\t}\n \t}\n+\tnvmet_blkcg_end(associated);\n \n \tnvmet_req_complete(req, status);\n }\n@@ -326,7 +334,7 @@ static void nvmet_file_execute_dsm(struct nvmet_req req)\n \tif (!nvmet_check_data_len_lte(req, nvmet_dsm_len(req)))\n \t\treturn;\n \tINIT_WORK(\u0026req-\u003ef.work, nvmet_file_dsm_work);\n-\tqueue_work(nvmet_wq, \u0026req-\u003ef.work);\n+\tnvmet_req_queue_work(req, nvmet_wq, \u0026req-\u003ef.work);\n }\n \n static void nvmet_file_write_zeroes_work(struct work_struct w)\n@@ -336,6 +344,7 @@ static void nvmet_file_write_zeroes_work(struct work_struct w)\n \tint mode = FALLOC_FL_ZERO_RANGE \| FALLOC_FL_KEEP_SIZE;\n \tloff_t offset;\n \tloff_t len;\n+\tbool associated;\n \tint ret;\n \n \toffset = le64_to_cpu(write_zeroes-\u003eslba) \u003c\u003c req-\u003ens-\u003eblksize_shift;\n@@ -347,7 +356,9 @@ static void nvmet_file_write_zeroes_work(struct work_struct w)\n \t\treturn;\n \t}\n \n+\tassociated = nvmet_blkcg_begin(req);\n \tret = vfs_fallocate(req-\u003ens-\u003efile, mode, offset, len);\n+\tnvmet_blkcg_end(associated);\n \tnvmet_req_complete(req, ret \u003c 0 ? errno_to_nvme_status(req, ret) : 0);\n }\n \n@@ -356,7 +367,7 @@ static void nvmet_file_execute_write_zeroes(struct nvmet_req req)\n \tif (!nvmet_check_transfer_len(req, 0))\n \t\treturn;\n \tINIT_WORK(\u0026req-\u003ef.work, nvmet_file_write_zeroes_work);\n-\tqueue_work(nvmet_wq, \u0026req-\u003ef.work);\n+\tnvmet_req_queue_work(req, nvmet_wq, \u0026req-\u003ef.work);\n }\n \n u16 nvmet_file_parse_io_cmd(struct nvmet_req req)\ndiff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h\nindex 9cec19e6f4857e..4eac1b5195a855 100644\n--- a/drivers/nvme/target/nvmet.h\n+++ b/drivers/nvme/target/nvmet.h\n@@ -117,6 +117,22 @@ struct nvmet_ns {\n \tstruct nvmet_subsys\tsubsys;\n \tconst char\t\tdevice_path;\n \n+#ifdef CONFIG_BLK_CGROUP\n+\tu64\t\t\tcgroup_id;\n+\t/\n+\t * Resolved from -\u003ecgroup_id when the namespace is enabled and\n+\t * released when it is disabled, so it has the same lifetime and\n+\t * visibility rules as -\u003ebdev and -\u003efile.\n+\t /\n+\tstruct cgroup\t\tcgrp;\n+\t/\n+\t The I/O commands of a namespace with a cgroup, except Reservation\n+\t * commands, are executed from their own work items on -\u003eblkcg_wq, so\n+\t * the cgroup's throttling doesn't put a transport context to sleep.\n+\t /\n+\tstruct workqueue_struct\tblkcg_wq;\n+#endif\n+\n \tstruct config_group\tdevice_group;\n \tstruct config_group\tgroup;\n \n@@ -509,6 +525,11 @@ struct nvmet_req {\n \n \tvoid (execute)(struct nvmet_req req);\n \tconst struct nvmet_fabrics_ops ops;\n+#ifdef CONFIG_BLK_CGROUP\n+\t/ the backend's -\u003eexecute, called from -\u003eblkcg_work /\n+\tvoid (blkcg_execute)(struct nvmet_req req);\n+\tstruct work_struct\tblkcg_work;\n+#endif\n \n \tstruct pci_dev\t\tp2p_dev;\n \tstruct device\t\tp2p_client;\n@@ -748,6 +769,36 @@ void nvmet_bdev_execute_zone_mgmt_recv(struct nvmet_req req);\n void nvmet_bdev_execute_zone_mgmt_send(struct nvmet_req req);\n void nvmet_bdev_execute_zone_append(struct nvmet_req req);\n \n+#ifdef CONFIG_BLK_CGROUP\n+bool nvmet_blkcg_begin(struct nvmet_req req);\n+void nvmet_blkcg_end(bool associated);\n+#else\n+static inline bool nvmet_blkcg_begin(struct nvmet_req req)\n+{\n+\treturn false;\n+}\n+\n+static inline void nvmet_blkcg_end(bool associated)\n+{\n+}\n+#endif /* CONFIG_BLK_CGROUP /\n+\n+/\n+ * The backends' work items of a namespace with a cgroup may sleep in the\n+ * cgroup's throttling, so queue them on the namespace's own workqueue,\n+ * where they can't use up the max_active or the rescuer of a workqueue\n+ * that other namespaces share.\n+ /\n+static inline void nvmet_req_queue_work(struct nvmet_req req,\n+\t\tstruct workqueue_struct wq, struct work_struct work)\n+{\n+#ifdef CONFIG_BLK_CGROUP\n+\tif (req-\u003ens-\u003eblkcg_wq)\n+\t\twq = req-\u003ens-\u003eblkcg_wq;\n+#endif\n+\tqueue_work(wq, work);\n+}\n+\n static inline u32 nvmet_rw_data_len(struct nvmet_req req)\n {\n \treturn ((u32)le16_to_cpu(req-\u003ecmd-\u003erw.length) + 1) \u003c\u003c\ndiff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c\nindex 78d82b6ff1214e..33faf32a1a3bfd 100644\n--- a/drivers/nvme/target/zns.c\n+++ b/drivers/nvme/target/zns.c\n@@ -490,8 +490,11 @@ static void nvmet_bdev_zmgmt_send_work(struct work_struct w)\n \tstruct block_device bdev = req-\u003ens-\u003ebdev;\n \tsector_t zone_sectors = bdev_zone_sectors(bdev);\n \tu16 status = NVME_SC_SUCCESS;\n+\tbool associated;\n \tint ret;\n \n+\tassociated = nvmet_blkcg_begin(req);\n+\n \tif (op == REQ_OP_LAST) {\n \t\treq-\u003eerror_loc = offsetof(struct nvme_zone_mgmt_send_cmd, zsa);\n \t\tstatus = NVME_SC_ZONE_INVALID_TRANSITION \| NVME_STATUS_DNR;\n@@ -521,13 +524,14 @@ static void nvmet_bdev_zmgmt_send_work(struct work_struct w)\n \t\tstatus = blkdev_zone_mgmt_errno_to_nvme_status(ret);\n \n out:\n+\tnvmet_blkcg_end(associated);\n \tnvmet_req_complete(req, status);\n }\n \n void nvmet_bdev_execute_zone_mgmt_send(struct nvmet_req req)\n {\n \tINIT_WORK(\u0026req-\u003ez.zmgmt_work, nvmet_bdev_zmgmt_send_work);\n-\tqueue_work(zbd_wq, \u0026req-\u003ez.zmgmt_work);\n+\tnvmet_req_queue_work(req, zbd_wq, \u0026req-\u003ez.zmgmt_work);\n }\n \n static void nvmet_bdev_zone_append_bio_done(struct bio bio)\n" }
2/1	2026/10/26 20:23	agent	patch-evaluator	1m Model: core Args: null Results: { "EnableConfigs": [ "NVME_TARGET", "BLK_CGROUP", "NVME_TARGET_LOOP", "CONFIGFS_FS" ], "FocusSymbols": [ "nvmet_ns_cgroup_id_store", "nvmet_blkcg_ns_enable", "nvmet_blkcg_ns_disable", "nvmet_blkcg_begin", "nvmet_blkcg_end", "nvmet_blkcg_work", "nvmet_ns_enable" ], "Reasoning": "The patch introduces cgroup v2 throttling and charging support for NVMe target (nvmet) namespaces. When a namespace is configured with a cgroup_id via configfs, I/O commands are dispatched through a dedicated per-namespace workqueue and associated with the cgroup's blkcg css via kthread_associate_blkcg. This code is fully reachable in standard virtualized QEMU environments using virtual/loopback transports (such as nvme-loop or nvmet-tcp over loopback). The changes add concurrency, asynchronous workqueue handling, cgroup refcounting, and teardown synchronization, which warrants fuzzing to detect potential race conditions or resource leaks.", "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 21158167c09894da68b4c04b907acbadceeeed2a Author: syz-cluster <triage@syzkaller.com> Date: Mon Oct 26 20:23:56 2026 +0000 syz-cluster: applied patch under review diff --git a/Documentation/ABI/stable/configfs-nvmet b/Documentation/ABI/stable/configfs-nvmet index 36b587404ee7ef..ea9c4083c6a0de 100644 --- a/Documentation/ABI/stable/configfs-nvmet +++ b/Documentation/ABI/stable/configfs-nvmet @@ -314,6 +314,22 @@ Description: attr_subsys_vendor_id: Shows or sets the PCI subsystem vendor ID. Displayed in "0x%x" format. +What: /config/nvmet/subsystems/NAME/namespaces/NSID/cgroup_id +Date: October 2026 +KernelVersion: 7.5 +Contact: Peng Yu <yupeng0921@gmail.com> +Description: + Shows or sets the cgroup2 ID of the cgroup to charge this + namespace's I/O to. Writing 0 clears it. The I/O is + charged to the cgroup's effective io css: the cgroup + itself or its nearest ancestor with the io controller + enabled. The namespace must be disabled before + modification. Enabling the namespace fails if the cgroup + can't be found or if buffered_io is set. A cgroup that is + removed and created again gets a new ID. + + Only available when CONFIG_BLK_CGROUP is enabled. + What: /config/nvmet/hosts/HOSTNQN/dhchap_key What: /config/nvmet/hosts/HOSTNQN/dhchap_ctrl_key What: /config/nvmet/hosts/HOSTNQN/dhchap_hash diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c index 8aea64d279c4af..9f0d48677c4a22 100644 --- a/drivers/nvme/target/configfs.c +++ b/drivers/nvme/target/configfs.c @@ -564,6 +564,50 @@ static ssize_t nvmet_ns_device_path_store(struct config_item item, CONFIGFS_ATTR(nvmet_ns_, device_path); +#ifdef CONFIG_BLK_CGROUP +static ssize_t nvmet_ns_cgroup_id_show(struct config_item item, char page) +{ + struct nvmet_ns ns = to_nvmet_ns(item); + struct nvmet_subsys subsys = ns->subsys; + ssize_t ret; + + mutex_lock(&subsys->lock); + ret = snprintf(page, PAGE_SIZE, "%llu\n", ns->cgroup_id); + mutex_unlock(&subsys->lock); + return ret; +} + +static ssize_t nvmet_ns_cgroup_id_store(struct config_item item, + const char page, size_t count) +{ + struct nvmet_ns ns = to_nvmet_ns(item); + struct nvmet_subsys subsys = ns->subsys; + u64 cgroup_id; + int ret; + + ret = kstrtou64(page, 0, &cgroup_id); + if (ret) + return ret; + + mutex_lock(&subsys->lock); + + if (ns->enabled) { + ret = -EBUSY; + goto out_unlock; + } + + / Writing 0 clears the association. / + ns->cgroup_id = cgroup_id; + ret = count; + +out_unlock: + mutex_unlock(&subsys->lock); + return ret; +} + +CONFIGFS_ATTR(nvmet_ns_, cgroup_id); +#endif / CONFIG_BLK_CGROUP / + #ifdef CONFIG_PCI_P2PDMA static ssize_t nvmet_ns_p2pmem_show(struct config_item item, char page) { @@ -836,6 +880,9 @@ static struct configfs_attribute nvmet_ns_attrs[] = { &nvmet_ns_attr_buffered_io, &nvmet_ns_attr_revalidate_size, &nvmet_ns_attr_resv_enable, +#ifdef CONFIG_BLK_CGROUP + &nvmet_ns_attr_cgroup_id, +#endif #ifdef CONFIG_PCI_P2PDMA &nvmet_ns_attr_p2pmem, #endif diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c index 8353950f346f3c..5472a8b3853ca8 100644 --- a/drivers/nvme/target/core.c +++ b/drivers/nvme/target/core.c @@ -4,12 +4,15 @@ * Copyright (c) 2015-2016 HGST, a Western Digital Company. / #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/cgroup.h> #include <linux/hex.h> +#include <linux/kthread.h> #include <linux/module.h> #include <linux/random.h> #include <linux/rculist.h> #include <linux/pci-p2pdma.h> #include <linux/scatterlist.h> +#include <linux/sched/mm.h> #include <generated/utsrelease.h> @@ -481,8 +484,144 @@ void nvmet_put_namespace(struct nvmet_ns ns) percpu_ref_put(&ns->ref); } +#ifdef CONFIG_BLK_CGROUP +static int nvmet_blkcg_ns_enable(struct nvmet_ns ns) +{ + struct cgroup cgrp; + + if (!ns->cgroup_id) + return 0; + + /* + * Buffered writes will be handled by a separate thread, + * these IOs have no namespace/cgroup information at that time, + * so we don't support buffered io. + / + if (ns->buffered_io) { + pr_err("cgroup_id is not supported with buffered_io: %s\n", + ns->device_path); + return -EINVAL; + } + + cgrp = cgroup_get_from_id(ns->cgroup_id); + if (IS_ERR(cgrp)) { + pr_err("failed to resolve cgroup id %llu: %ld\n", + ns->cgroup_id, PTR_ERR(cgrp)); + return PTR_ERR(cgrp); + } + + ns->blkcg_wq = alloc_workqueue("nvmet-blkcg-%u", + WQ_MEM_RECLAIM \| WQ_UNBOUND, num_online_cpus(), + ns->nsid); + if (!ns->blkcg_wq) { + cgroup_put(cgrp); + return -ENOMEM; + } + + ns->cgrp = cgrp; + return 0; +} + +static void nvmet_blkcg_ns_disable(struct nvmet_ns ns) +{ + if (ns->cgrp) { + /* + * No command is left, but the work item of a command that + * completed from inside ->blkcg_execute() may still be + * returning: destroy_workqueue() waits for it. + / + destroy_workqueue(ns->blkcg_wq); + ns->blkcg_wq = NULL; + cgroup_put(ns->cgrp); + ns->cgrp = NULL; + } +} + +/ + * Charge the I/O that the current work item submits for @req to the + * effective io css of the namespace's cgroup, looked up for each command. + / +bool nvmet_blkcg_begin(struct nvmet_req req) +{ + struct nvmet_ns ns = req->ns; + struct cgroup_subsys_state css; + + /* a disable waits for the command: don't throttle it any more / + if (!ns->cgrp \|\| !READ_ONCE(ns->enabled)) + return false; + + css = cgroup_get_e_css(ns->cgrp, &io_cgrp_subsys); + kthread_associate_blkcg(css); + css_put(css); + return true; +} + +void nvmet_blkcg_end(bool associated) +{ + if (associated) + kthread_associate_blkcg(NULL); +} + +/ + * The io.cost and io.latency enforce their limits by putting the thread to + * sleep. A transport thread may be shared by multiple namespaces. In the + * tcp-nvmeof case, all namespaces in the same subsystem may share a + * thread. So we submit the IOs via the workqueue, thus the current thread + * won't be blocked. + / +static void nvmet_blkcg_work(struct work_struct work) +{ + struct nvmet_req req = + container_of(work, struct nvmet_req, blkcg_work); + unsigned int noio_flag; + bool associated; + + / its queue is being deleted: abort it rather than throttle it / + if (unlikely(percpu_ref_is_dying(&req->sq->ref))) { + nvmet_req_complete(req, NVME_SC_ABORT_QUEUE); + return; + } + + / reclaim must not wait for I/O queued on this workqueue / + noio_flag = memalloc_noio_save(); + associated = nvmet_blkcg_begin(req); + req->blkcg_execute(req); + nvmet_blkcg_end(associated); + memalloc_noio_restore(noio_flag); +} + +static void nvmet_blkcg_queue_req(struct nvmet_req req) +{ + INIT_WORK(&req->blkcg_work, nvmet_blkcg_work); + queue_work(req->ns->blkcg_wq, &req->blkcg_work); +} + +static void nvmet_blkcg_init_req(struct nvmet_req req) +{ + if (!req->ns->cgrp) + return; + + req->blkcg_execute = req->execute; + req->execute = nvmet_blkcg_queue_req; +} +#else +static inline int nvmet_blkcg_ns_enable(struct nvmet_ns ns) +{ + return 0; +} + +static inline void nvmet_blkcg_ns_disable(struct nvmet_ns ns) +{ +} + +static inline void nvmet_blkcg_init_req(struct nvmet_req req) +{ +} +#endif /* CONFIG_BLK_CGROUP / + static void nvmet_ns_dev_disable(struct nvmet_ns ns) { + nvmet_blkcg_ns_disable(ns); nvmet_bdev_ns_disable(ns); nvmet_file_ns_disable(ns); } @@ -609,6 +748,10 @@ int nvmet_ns_enable(struct nvmet_ns ns) if (ret) goto out_unlock; + ret = nvmet_blkcg_ns_enable(ns); + if (ret) + goto out_dev_disable; + ret = nvmet_p2pmem_ns_enable(ns); if (ret) goto out_dev_disable; @@ -1165,6 +1308,8 @@ static u16 nvmet_parse_io_cmd(struct nvmet_req req) if (ret) return ret; + nvmet_blkcg_init_req(req); + if (req->ns->pr.enable) { ret = nvmet_pr_check_cmd_access(req); if (ret) diff --git a/drivers/nvme/target/io-cmd-file.c b/drivers/nvme/target/io-cmd-file.c index 695963dd932ee7..673df713c954f9 100644 --- a/drivers/nvme/target/io-cmd-file.c +++ b/drivers/nvme/target/io-cmd-file.c @@ -257,8 +257,13 @@ u16 nvmet_file_flush(struct nvmet_req req) static void nvmet_file_flush_work(struct work_struct w) { struct nvmet_req req = container_of(w, struct nvmet_req, f.work); + bool associated; + u16 status; - nvmet_req_complete(req, nvmet_file_flush(req)); + associated = nvmet_blkcg_begin(req); + status = nvmet_file_flush(req); + nvmet_blkcg_end(associated); + nvmet_req_complete(req, status); } static void nvmet_file_execute_flush(struct nvmet_req req) @@ -266,7 +271,7 @@ static void nvmet_file_execute_flush(struct nvmet_req req) if (!nvmet_check_transfer_len(req, 0)) return; INIT_WORK(&req->f.work, nvmet_file_flush_work); - queue_work(nvmet_wq, &req->f.work); + nvmet_req_queue_work(req, nvmet_wq, &req->f.work); } static void nvmet_file_execute_discard(struct nvmet_req req) @@ -274,10 +279,12 @@ static void nvmet_file_execute_discard(struct nvmet_req req) int mode = FALLOC_FL_PUNCH_HOLE \| FALLOC_FL_KEEP_SIZE; struct nvme_dsm_range range; loff_t offset, len; + bool associated; u16 status = 0; int ret; int i; + associated = nvmet_blkcg_begin(req); for (i = 0; i <= le32_to_cpu(req->cmd->dsm.nr); i++) { status = nvmet_copy_from_sgl(req, i sizeof(range), &range, sizeof(range)); @@ -300,6 +307,7 @@ static void nvmet_file_execute_discard(struct nvmet_req req) break; } } + nvmet_blkcg_end(associated); nvmet_req_complete(req, status); } @@ -326,7 +334,7 @@ static void nvmet_file_execute_dsm(struct nvmet_req req) if (!nvmet_check_data_len_lte(req, nvmet_dsm_len(req))) return; INIT_WORK(&req->f.work, nvmet_file_dsm_work); - queue_work(nvmet_wq, &req->f.work); + nvmet_req_queue_work(req, nvmet_wq, &req->f.work); } static void nvmet_file_write_zeroes_work(struct work_struct w) @@ -336,6 +344,7 @@ static void nvmet_file_write_zeroes_work(struct work_struct w) int mode = FALLOC_FL_ZERO_RANGE \| FALLOC_FL_KEEP_SIZE; loff_t offset; loff_t len; + bool associated; int ret; offset = le64_to_cpu(write_zeroes->slba) << req->ns->blksize_shift; @@ -347,7 +356,9 @@ static void nvmet_file_write_zeroes_work(struct work_struct w) return; } + associated = nvmet_blkcg_begin(req); ret = vfs_fallocate(req->ns->file, mode, offset, len); + nvmet_blkcg_end(associated); nvmet_req_complete(req, ret < 0 ? errno_to_nvme_status(req, ret) : 0); } @@ -356,7 +367,7 @@ static void nvmet_file_execute_write_zeroes(struct nvmet_req req) if (!nvmet_check_transfer_len(req, 0)) return; INIT_WORK(&req->f.work, nvmet_file_write_zeroes_work); - queue_work(nvmet_wq, &req->f.work); + nvmet_req_queue_work(req, nvmet_wq, &req->f.work); } u16 nvmet_file_parse_io_cmd(struct nvmet_req req) diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h index 9cec19e6f4857e..4eac1b5195a855 100644 --- a/drivers/nvme/target/nvmet.h +++ b/drivers/nvme/target/nvmet.h @@ -117,6 +117,22 @@ struct nvmet_ns { struct nvmet_subsys subsys; const char device_path; +#ifdef CONFIG_BLK_CGROUP + u64 cgroup_id; + / + * Resolved from ->cgroup_id when the namespace is enabled and + * released when it is disabled, so it has the same lifetime and + * visibility rules as ->bdev and ->file. + / + struct cgroup cgrp; + /* + * The I/O commands of a namespace with a cgroup, except Reservation + * commands, are executed from their own work items on ->blkcg_wq, so + * the cgroup's throttling doesn't put a transport context to sleep. + / + struct workqueue_struct blkcg_wq; +#endif + struct config_group device_group; struct config_group group; @@ -509,6 +525,11 @@ struct nvmet_req { void (execute)(struct nvmet_req req); const struct nvmet_fabrics_ops ops; +#ifdef CONFIG_BLK_CGROUP + / the backend's ->execute, called from ->blkcg_work / + void (blkcg_execute)(struct nvmet_req req); + struct work_struct blkcg_work; +#endif struct pci_dev p2p_dev; struct device p2p_client; @@ -748,6 +769,36 @@ void nvmet_bdev_execute_zone_mgmt_recv(struct nvmet_req req); void nvmet_bdev_execute_zone_mgmt_send(struct nvmet_req req); void nvmet_bdev_execute_zone_append(struct nvmet_req req); +#ifdef CONFIG_BLK_CGROUP +bool nvmet_blkcg_begin(struct nvmet_req req); +void nvmet_blkcg_end(bool associated); +#else +static inline bool nvmet_blkcg_begin(struct nvmet_req req) +{ + return false; +} + +static inline void nvmet_blkcg_end(bool associated) +{ +} +#endif /* CONFIG_BLK_CGROUP / + +/ + * The backends' work items of a namespace with a cgroup may sleep in the + * cgroup's throttling, so queue them on the namespace's own workqueue, + * where they can't use up the max_active or the rescuer of a workqueue + * that other namespaces share. + / +static inline void nvmet_req_queue_work(struct nvmet_req req, + struct workqueue_struct wq, struct work_struct work) +{ +#ifdef CONFIG_BLK_CGROUP + if (req->ns->blkcg_wq) + wq = req->ns->blkcg_wq; +#endif + queue_work(wq, work); +} + static inline u32 nvmet_rw_data_len(struct nvmet_req req) { return ((u32)le16_to_cpu(req->cmd->rw.length) + 1) << diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c index 78d82b6ff1214e..33faf32a1a3bfd 100644 --- a/drivers/nvme/target/zns.c +++ b/drivers/nvme/target/zns.c @@ -490,8 +490,11 @@ static void nvmet_bdev_zmgmt_send_work(struct work_struct w) struct block_device bdev = req->ns->bdev; sector_t zone_sectors = bdev_zone_sectors(bdev); u16 status = NVME_SC_SUCCESS; + bool associated; int ret; + associated = nvmet_blkcg_begin(req); + if (op == REQ_OP_LAST) { req->error_loc = offsetof(struct nvme_zone_mgmt_send_cmd, zsa); status = NVME_SC_ZONE_INVALID_TRANSITION \| NVME_STATUS_DNR; @@ -521,13 +524,14 @@ static void nvmet_bdev_zmgmt_send_work(struct work_struct w) status = blkdev_zone_mgmt_errno_to_nvme_status(ret); out: + nvmet_blkcg_end(associated); nvmet_req_complete(req, status); } void nvmet_bdev_execute_zone_mgmt_send(struct nvmet_req req) { INIT_WORK(&req->z.zmgmt_work, nvmet_bdev_zmgmt_send_work); - queue_work(zbd_wq, &req->z.zmgmt_work); + nvmet_req_queue_work(req, zbd_wq, &req->z.zmgmt_work); } static void nvmet_bdev_zone_append_bio_done(struct bio bio)
3/2	2026/10/26 20:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 8719 output: 35 thoughts: 255 Thoughts: Analyzing This Kernel Patch Series Okay, so I need to evaluate this patch series for the kernel, specifically targeting the amd64 architecture. Let's dive right in and dissect these changes. First, I need to look at the diff and pinpoint exactly what's being modified. It looks like this touches quite a few files: `Documentation/ABI/stable/configfs-nvmet`, and then files in `drivers/nvme/target/` – specifically `configfs.c`, `core.c`, `io-cmd-file.c`, `nvmet.h`, and `zns.c`. Ah, this is all related to NVMe Target, or `nvmet`, then. Now, my initial question is, how accessible is this NVMe Target functionality? Is it something I can readily test in standard virtualized environments like QEMU? Thankfully, the answer is yes. NVMe-oF (NVMe over Fabrics) target, particularly the `nvme-loop` transport, but also `nvmet-tcp` and `nvmet-rdma`, are commonly tested and fuzzed within standard Linux setups and syzkaller. To get a clearer picture, I need to verify how `nvmet` functions and which Kconfig options are relevant. I'll need to understand if this is emulated, virtualized, or relies on special hardware. The key is confirming whether I can reach this from userspace without requiring any special physical hardware. Time to search for the nvmet configuration and how it's being used.
4/2	2026/10/26 20:24	tool	grepper	0m Args: { "Expression": "config NVME_TARGET", "PathPrefixes": [ "drivers/nvme/target/Kconfig" ] } Results: { "Output": "drivers/nvme/target/Kconfig-2-\ndrivers/nvme/target/Kconfig:3:config NVME_TARGET\ndrivers/nvme/target/Kconfig-4-\ttristate \"NVMe Target support\"\n--\ndrivers/nvme/target/Kconfig-19-\ndrivers/nvme/target/Kconfig:20:config NVME_TARGET_DEBUGFS\ndrivers/nvme/target/Kconfig-21- bool \"NVMe Target debugfs support\"\n--\ndrivers/nvme/target/Kconfig-28-\ndrivers/nvme/target/Kconfig:29:config NVME_TARGET_PASSTHRU\ndrivers/nvme/target/Kconfig-30-\tbool \"NVMe Target Passthrough support\"\n--\ndrivers/nvme/target/Kconfig-40-\ndrivers/nvme/target/Kconfig:41:config NVME_TARGET_LOOP\ndrivers/nvme/target/Kconfig-42-\ttristate \"NVMe loopback device support\"\n--\ndrivers/nvme/target/Kconfig-51-\ndrivers/nvme/target/Kconfig:52:config NVME_TARGET_RDMA\ndrivers/nvme/target/Kconfig-53-\ttristate \"NVMe over Fabrics RDMA target support\"\n--\ndrivers/nvme/target/Kconfig-62-\ndrivers/nvme/target/Kconfig:63:config NVME_TARGET_FC\ndrivers/nvme/target/Kconfig-64-\ttristate \"NVMe over Fabrics FC target driver\"\n--\ndrivers/nvme/target/Kconfig-73-\ndrivers/nvme/target/Kconfig:74:config NVME_TARGET_FCLOOP\ndrivers/nvme/target/Kconfig-75-\ttristate \"NVMe over Fabrics FC Transport Loopback Test driver\"\n--\ndrivers/nvme/target/Kconfig-86-\ndrivers/nvme/target/Kconfig:87:config NVME_TARGET_TCP\ndrivers/nvme/target/Kconfig-88-\ttristate \"NVMe over Fabrics TCP target support\"\n--\ndrivers/nvme/target/Kconfig-96-\ndrivers/nvme/target/Kconfig:97:config NVME_TARGET_TCP_TLS\ndrivers/nvme/target/Kconfig-98-\tbool \"NVMe over Fabrics TCP target TLS encryption support\"\n--\ndrivers/nvme/target/Kconfig-109-\ndrivers/nvme/target/Kconfig:110:config NVME_TARGET_AUTH\ndrivers/nvme/target/Kconfig-111-\tbool \"NVMe over Fabrics In-band Authentication in target side\"\n--\ndrivers/nvme/target/Kconfig-119-\ndrivers/nvme/target/Kconfig:120:config NVME_TARGET_AUTH_DEBUG\ndrivers/nvme/target/Kconfig-121-\tbool \"NVMe over Fabrics In-band Authentication debug messages\"\n--\ndrivers/nvme/target/Kconfig-128-\ndrivers/nvme/target/Kconfig:129:config NVME_TARGET_PCI_EPF\ndrivers/nvme/target/Kconfig-130-\ttristate \"NVMe PCI Endpoint Function target support\"\n" }
5/2	2026/10/26 20:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10128 output: 35 thoughts: 52 Thoughts: Here's my take on the situation: NVMe Target Configuration - A Quick Check Okay, so `NVME_TARGET` is the big kahuna, the central config for this new NVMe target functionality. Got it. But there's also `CONFIG_BLK_CGROUP` lurking in the background, it's a requirement for the new feature! Right, important. Now I need to quickly verify my understanding. Let's dive into `drivers/nvme/target/Kconfig`. I'll zero in on the sections surrounding `NVME_TARGET` and make sure I haven't missed anything critical, particularly around the dependency on `CONFIG_BLK_CGROUP`. It's always the dependencies that trip you up, and I don't want to waste time debugging something I've overlooked.
6/2	2026/10/26 20:24	tool	read-file	0m Args: { "File": "drivers/nvme/target/Kconfig", "FirstLine": 1, "LineCount": 50 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\t\n 3:\tconfig NVME_TARGET\n 4:\t\ttristate \"NVMe Target support\"\n 5:\t\tdepends on BLOCK\n 6:\t\tselect CONFIGFS_FS\n 7:\t\tselect NVME_KEYRING if NVME_TARGET_TCP_TLS\n 8:\t\tselect KEYS if NVME_TARGET_TCP_TLS\n 9:\t\tselect SGL_ALLOC\n 10:\t\thelp\n 11:\t\t This enabled target side support for the NVMe protocol, that is\n 12:\t\t it allows the Linux kernel to implement NVMe subsystems and\n 13:\t\t controllers and export Linux block devices as NVMe namespaces.\n 14:\t\t You need to select at least one of the transports below to make this\n 15:\t\t functionality useful.\n 16:\t\n 17:\t\t To configure the NVMe target you probably want to use the nvmetcli\n 18:\t\t tool from http://git.infradead.org/users/hch/nvmetcli.git.\n 19:\t\n 20:\tconfig NVME_TARGET_DEBUGFS\n 21:\t bool \"NVMe Target debugfs support\"\n 22:\t\tdepends on NVME_TARGET\n 23:\t\thelp\n 24:\t\t This enables debugfs support to display the connected controllers\n 25:\t\t to each subsystem\n 26:\t\n 27:\t\t If unsure, say N.\n 28:\t\n 29:\tconfig NVME_TARGET_PASSTHRU\n 30:\t\tbool \"NVMe Target Passthrough support\"\n 31:\t\tdepends on NVME_TARGET\n 32:\t\tdepends on NVME_CORE=y \|\| NVME_CORE=NVME_TARGET\n 33:\t\thelp\n 34:\t\t This enables target side NVMe passthru controller support for the\n 35:\t\t NVMe Over Fabrics protocol. It allows for hosts to manage and\n 36:\t\t directly access an actual NVMe controller residing on the target\n 37:\t\t side, including executing Vendor Unique Commands.\n 38:\t\n 39:\t\t If unsure, say N.\n 40:\t\n 41:\tconfig NVME_TARGET_LOOP\n 42:\t\ttristate \"NVMe loopback device support\"\n 43:\t\tdepends on NVME_TARGET\n 44:\t\tselect NVME_FABRICS\n 45:\t\tselect SG_POOL\n 46:\t\thelp\n 47:\t\t This enables the NVMe loopback device support, which can be useful\n 48:\t\t to test NVMe host and target side features.\n 49:\t\n 50:\t\t If unsure, say N.\n" }
7/2	2026/10/26 20:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 11078 output: 38 thoughts: 1271 Thoughts: Analyzing NVMe-oF Target cgroup Integration for Fuzzing Potential Okay, let's dive into this NVMe-oF target cgroup integration. First, I need to check if syzkaller already has descriptions for nvmet or configfs nvmet. Then, I need to confirm if configfs itself can be used to configure nvmet. Using configfs (`/config/nvmet/...`), userspace creates subsystems, ports, namespaces, etc. The NVME_TARGET_LOOP module seems crucial because it lets us connect a virtual NVMe device loopback to the nvmet target! There's also NVME_TARGET_TCP, which allows connection over a loopback network interface via TCP! This new patch introduces cgroup_id configuration via configfs: `/config/nvmet/subsystems/NAME/namespaces/NSID/cgroup_id`. When enabled, it associates I/O with the specified cgroup using `kthread_associate_blkcg(css)`. A workqueue `ns->blkcg_wq = alloc_workqueue("nvmet-blkcg-%u", ...)` is allocated. The `nvmet_blkcg_work` function looks interesting for analysis because of the percpu_ref checks and noio handling: ```c /* its queue is being deleted: abort it rather than throttle it / if (unlikely(percpu_ref_is_dying(&req->sq->ref))) { nvmet_req_complete(req, NVME_SC_ABORT_QUEUE); return; } / reclaim must not wait for I/O queued on this workqueue */ noio_flag = memalloc_noio_save(); associated = nvmet_blkcg_begin(req); req->blkcg_execute(req); nvmet_blkcg_end(associated); memalloc_noio_restore(noio_flag); ``` Then, in `nvmet_parse_io_cmd`: ```c nvmet_blkcg_init_req(req); ``` `nvmet_blkcg_init_req` is the interesting part, which sets up the cgroup integration by replacing the execute function of a request with `nvmet_blkcg_queue_req` when a cgroup is configured. The `io-cmd-file.c` calls `nvmet_blkcg_begin(req)` and `nvmet_blkcg_end(associated)`, and it also uses `nvmet_req_queue_work`. `zns.c` also calls `nvmet_blkcg_begin(req)` and `nvmet_blkcg_end(associated)`. Alright, let's see if syzkaller supports nvmet configfs or nvme-loop out-of-the-box or if we can use configfs for fuzzing. I'll search the tree, commit messages, and tests. Wait, I should first check how syzkaller interacts with configfs and nvmet. Aha! Syzkaller does have configfs support and can interact with `/config/nvmet/...` by writing to configfs through open/write/mkdir. Furthermore, loopback nvme (`nvme-loop`) can be setup via configfs and `/dev/nvme-fabrics`. Is all of this reachable in standard virtualized environments like QEMU? Yes! The NVMe Target is pure software. It runs on loopback block devices, ramdisks, file-backed namespaces, or virtual block devices, and over nvme-loop or nvme-tcp (over lo). No physical PCIe ASIC or hardware is needed! Now, let's examine the patch details more carefully, looking for specific aspects, potential bugs, and subtleties. I'll list the introduced or modified functions: 1. `nvmet_ns_cgroup_id_show` 2. `nvmet_ns_cgroup_id_store` 3. `nvmet_blkcg_ns_enable` 4. `nvmet_blkcg_ns_disable` 5. `nvmet_blkcg_begin` 6. `nvmet_blkcg_end` 7. `nvmet_blkcg_work` 8. `nvmet_blkcg_queue_req` 9. `nvmet_blkcg_init_req` 10. `nvmet_ns_dev_disable` 11. `nvmet_ns_enable` 12. `nvmet_parse_io_cmd` 13. `nvmet_file_flush_work` 14. `nvmet_file_execute
8/2	2026/10/26 20:24	tool	grepper	0m Args: { "Expression": "int nvmet_ns_enable", "PathPrefixes": [ "drivers/nvme/target/core.c" ] } Results: { "Output": "drivers/nvme/target/core.c=711=bool nvmet_ns_revalidate(struct nvmet_ns ns)\n--\ndrivers/nvme/target/core.c-722-\ndrivers/nvme/target/core.c:723:int nvmet_ns_enable(struct nvmet_ns ns)\ndrivers/nvme/target/core.c-724-{\n" }
9/2	2026/10/26 20:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 13523 output: 38 thoughts: 23 Thoughts: Okay, let's dive into this. Here's my thought process on the matter: Analyzing `nvmet_ns_enable` Alright, I need to get a handle on the `nvmet_ns_enable` function. To fully understand its role, I'll focus my attention on the code between lines 720 and 770. That's usually a good range to start, gives me a manageable chunk to dissect without getting lost in the broader context immediately. I'm expecting this section to reveal the core logic behind enabling a namespace within the NVMe subsystem. I'm looking for the essential steps: any checks for pre-conditions, the critical data structures being modified, and the general flow control to either activate or reject the enable operation. My initial assumption is it deals with resource allocation or mapping, but I'll reserve judgment until I review this specific code.
10/2	2026/10/26 20:24	tool	read-file	0m Args: { "File": "drivers/nvme/target/core.c", "FirstLine": 720, "LineCount": 60 } Results: { "Contents": " 720:\t\treturn oldsize != ns-\u003esize;\n 721:\t}\n 722:\t\n 723:\tint nvmet_ns_enable(struct nvmet_ns ns)\n 724:\t{\n 725:\t\tstruct nvmet_subsys subsys = ns-\u003esubsys;\n 726:\t\tstruct nvmet_ctrl *ctrl;\n 727:\t\tint ret;\n 728:\t\n 729:\t\tmutex_lock(\u0026subsys-\u003elock);\n 730:\t\tret = 0;\n 731:\t\n 732:\t\tif (nvmet_is_passthru_subsys(subsys)) {\n 733:\t\t\tpr_info(\"cannot enable both passthru and regular namespaces for a single subsystem\");\n 734:\t\t\tgoto out_unlock;\n 735:\t\t}\n 736:\t\n 737:\t\tif (ns-\u003eenabled)\n 738:\t\t\tgoto out_unlock;\n 739:\t\n 740:\t\tif (!ns-\u003edevice_path) {\n 741:\t\t\tret = -EINVAL;\n 742:\t\t\tgoto out_unlock;\n 743:\t\t}\n 744:\t\n 745:\t\tret = nvmet_bdev_ns_enable(ns);\n 746:\t\tif (ret == -ENOTBLK)\n 747:\t\t\tret = nvmet_file_ns_enable(ns);\n 748:\t\tif (ret)\n 749:\t\t\tgoto out_unlock;\n 750:\t\n 751:\t\tret = nvmet_blkcg_ns_enable(ns);\n 752:\t\tif (ret)\n 753:\t\t\tgoto out_dev_disable;\n 754:\t\n 755:\t\tret = nvmet_p2pmem_ns_enable(ns);\n 756:\t\tif (ret)\n 757:\t\t\tgoto out_dev_disable;\n 758:\t\n 759:\t\tlist_for_each_entry(ctrl, \u0026subsys-\u003ectrls, subsys_entry)\n 760:\t\t\tnvmet_p2pmem_ns_add_p2p(ctrl, ns);\n 761:\t\n 762:\t\tif (ns-\u003epr.enable) {\n 763:\t\t\tret = nvmet_pr_init_ns(ns);\n 764:\t\t\tif (ret)\n 765:\t\t\t\tgoto out_dev_put;\n 766:\t\t}\n 767:\t\n 768:\t\tret = percpu_ref_init(\u0026ns-\u003eref, nvmet_destroy_namespace, 0, GFP_KERNEL);\n 769:\t\tif (ret)\n 770:\t\t\tgoto out_pr_exit;\n 771:\t\n 772:\t\tnvmet_ns_changed(subsys, ns-\u003ensid);\n 773:\t\tns-\u003eenabled = true;\n 774:\t\txa_set_mark(\u0026subsys-\u003enamespaces, ns-\u003ensid, NVMET_NS_ENABLED);\n 775:\t\tnvmet_debugfs_ns_setup(ns);\n 776:\t\tset_bit(NVMET_NS_IO_LIVE, \u0026ns-\u003eflags);\n 777:\t\tret = 0;\n 778:\tout_unlock:\n 779:\t\tmutex_unlock(\u0026subsys-\u003elock);\n" }
11/2	2026/10/26 20:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14651 output: 35 thoughts: 625 Thoughts: Analyzing Potential Race Conditions in NVMe Namespace Disabling Okay, let's break this down. I'm looking at the error handling path during NVMe namespace removal and I see a potential issue with cgroup interactions. First, I'm examining the `out_pr_exit`, `out_dev_put`, and `out_dev_disable` code paths. It seems pretty straightforward; `nvmet_ns_dev_disable` is called which in turn calls a few `nvmet__ns_disable` functions. `nvmet_ns_dev_disable` calls `nvmet_blkcg_ns_disable(ns)`. The concern arises if `nvmet_blkcg_ns_enable` fails, particularly during workqueue allocation. It looks like it could call `cgroup_put(cgrp)` and return `-ENOMEM`, then go to the `out_dev_disable` label. This means `nvmet_blkcg_ns_disable` is called, but crucial state might be missing. Right, the code in `nvmet_blkcg_ns_enable` hasn't yet set `ns->cgrp`. So in this failure path, `nvmet_blkcg_ns_disable` currently does nothing* because `ns->cgrp` is still NULL. However, that's not the main issue. The critical race lies if `nvmet_p2pmem_ns_enable` fails. It looks like the same clean-up is done - `nvmet_blkcg_ns_disable` is called, and this does a `cgroup_put`! I think the code is trying to handle situations where `nvmet_p2pmem_ns_enable` might fail and should call the clean up code for the cgroup. That `cgroup_put` call can destroy the workqueue. Then, I'm shifting my focus to `nvmet_blkcg_begin`. This function is responsible for initiating a block cgroup context for an NVMe request. I see a `cgroup_get_e_css(ns->cgrp, &io_cgrp_subsys);` call. The crucial point here is that if a disable operation is in progress, the command should not be throttled anymore. But wait, `cgroup_get_e_css` could fail, if the `io_cgrp_subsys` subsystem is not initialized. I need to make sure `io_cgrp_subsys` is always ready when `CONFIG_BLK_CGROUP` is enabled. It's time to check where `io_cgrp_subsys` is defined and how its lifecycle is managed. I must verify if `io_cgrp_subsys` is always available.
12/2	2026/10/26 20:24	tool	grepper	0m Args: { "Expression": "io_cgrp_subsys", "PathPrefixes": [ "block/", "include/" ] } Results: { "Output": "block/bfq-iosched.c=6237=static void bfq_insert_request(struct blk_mq_hw_ctx hctx, struct request rq,\n--\nblock/bfq-iosched.c-6247-#ifdef CONFIG_BFQ_GROUP_IOSCHED\nblock/bfq-iosched.c:6248:\tif (!cgroup_subsys_on_dfl(io_cgrp_subsys) \u0026\u0026 rq-\u003ebio)\nblock/bfq-iosched.c-6249-\t\tbfqg_stats_update_legacy_io(q, rq);\n--\nblock/blk-cgroup-fc-appid.c=11=int blkcg_set_fc_appid(char app_id, u64 cgrp_id, size_t app_id_len)\n--\nblock/blk-cgroup-fc-appid.c-23-\t\treturn PTR_ERR(cgrp);\nblock/blk-cgroup-fc-appid.c:24:\tcss = cgroup_get_e_css(cgrp, \u0026io_cgrp_subsys);\nblock/blk-cgroup-fc-appid.c-25-\tif (!css) {\n--\nblock/blk-cgroup.c=1524=static void blkcg_exit(struct task_struct tsk)\n--\nblock/blk-cgroup.c-1530-\nblock/blk-cgroup.c:1531:struct cgroup_subsys io_cgrp_subsys = {\nblock/blk-cgroup.c-1532-\t.css_alloc = blkcg_css_alloc,\n--\nblock/blk-cgroup.c-1549-};\nblock/blk-cgroup.c:1550:EXPORT_SYMBOL_GPL(io_cgrp_subsys);\nblock/blk-cgroup.c-1551-\n--\nblock/blk-cgroup.c=1751=int blkcg_policy_register(struct blkcg_policy pol)\n--\nblock/blk-cgroup.c-1801-\tif (pol-\u003edfl_cftypes == pol-\u003elegacy_cftypes) {\nblock/blk-cgroup.c:1802:\t\tWARN_ON(cgroup_add_cftypes(\u0026io_cgrp_subsys,\nblock/blk-cgroup.c-1803-\t\t\t\t\t pol-\u003edfl_cftypes));\nblock/blk-cgroup.c-1804-\t} else {\nblock/blk-cgroup.c:1805:\t\tWARN_ON(cgroup_add_dfl_cftypes(\u0026io_cgrp_subsys,\nblock/blk-cgroup.c-1806-\t\t\t\t\t pol-\u003edfl_cftypes));\nblock/blk-cgroup.c:1807:\t\tWARN_ON(cgroup_add_legacy_cftypes(\u0026io_cgrp_subsys,\nblock/blk-cgroup.c-1808-\t\t\t\t\t\t pol-\u003elegacy_cftypes));\n--\nblock/blk-cgroup.c=2208=void blk_cgroup_bio_start(struct bio bio)\n--\nblock/blk-cgroup.c-2214-\nblock/blk-cgroup.c:2215:\tif (!cgroup_subsys_on_dfl(io_cgrp_subsys))\nblock/blk-cgroup.c-2216-\t\treturn;\n--\nblock/blk-throttle.c=84=static uint64_t tg_bps_limit(struct throtl_grp tg, int rw)\n--\nblock/blk-throttle.c-87-\nblock/blk-throttle.c:88:\tif (cgroup_subsys_on_dfl(io_cgrp_subsys) \u0026\u0026 !blkg-\u003eparent)\nblock/blk-throttle.c-89-\t\treturn U64_MAX;\n--\nblock/blk-throttle.c=94=static unsigned int tg_iops_limit(struct throtl_grp tg, int rw)\n--\nblock/blk-throttle.c-97-\nblock/blk-throttle.c:98:\tif (cgroup_subsys_on_dfl(io_cgrp_subsys) \u0026\u0026 !blkg-\u003eparent)\nblock/blk-throttle.c-99-\t\treturn UINT_MAX;\n--\nblock/blk-throttle.c=299=static void throtl_pd_init(struct blkg_policy_data pd)\n--\nblock/blk-throttle.c-320-\tsq-\u003eparent_sq = \u0026td-\u003eservice_queue;\nblock/blk-throttle.c:321:\tif (cgroup_subsys_on_dfl(io_cgrp_subsys) \u0026\u0026 blkg-\u003eparent)\nblock/blk-throttle.c-322-\t\tsq-\u003eparent_sq = \u0026blkg_to_tg(blkg-\u003eparent)-\u003eservice_queue;\n--\nblock/blk-throttle.c=1270=static void tg_conf_updated(struct throtl_grp tg, bool global)\n--\nblock/blk-throttle.c-1294-\t\t/* ignore root/second level /\nblock/blk-throttle.c:1295:\t\tif (!cgroup_subsys_on_dfl(io_cgrp_subsys) \|\| !blkg-\u003eparent \|\|\nblock/blk-throttle.c-1296-\t\t !blkg-\u003eparent-\u003eparent)\n--\nblock/blk-throttle.h=166=static inline bool blk_should_throtl(struct bio bio)\n--\nblock/blk-throttle.h-174-\ttg = blkg_to_tg(bio-\u003ebi_blkg);\nblock/blk-throttle.h:175:\tif (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {\nblock/blk-throttle.h-176-\t\tif (!bio_flagged(bio, BIO_CGROUP_ACCT)) {\n--\ninclude/linux/backing-dev.h=171=static inline bool inode_cgwb_enabled(struct inode *inode)\n--\ninclude/linux/backing-dev.h-175-\treturn cgroup_subsys_on_dfl(memory_cgrp_subsys) \u0026\u0026\ninclude/linux/backing-dev.h:176:\t\tcgroup_subsys_on_dfl(io_cgrp_subsys) \u0026\u0026\ninclude/linux/backing-dev.h-177-\t\t(bdi-\u003ecapabilities \u0026 BDI_CAP_WRITEBACK) \u0026\u0026\n" }
13/2	2026/10/26 20:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17526 output: 21 thoughts: 37 Thoughts: Okay, here's my interpretation of that thought process, assuming I'm an expert in this area: Analyzing the Block I/O Cgroup Subsystem Dependency Right, let me see...so, `io_cgrp_subsys` is only exposed when `CONFIG_BLK_CGROUP` is on. That's the baseline. It makes sense; the cgroup subsystem for I/O needs to be compiled into the kernel for the relevant structures and functions to be available. Now, the key is understanding how everything hooks up. The critical part is now to analyze `kthread_associate_blkcg`. That's where the rubber hits the road. I need to figure out how threads, specifically kernel threads (since we're looking at a function name with "kthread"), get linked to the block I/O cgroup context. I need to understand how the association between a kernel thread and a block I/O cgroup is established and maintained. Is it done eagerly, lazily, or upon some specific event? And what are the implications of this association? Performance? Resource allocation? This function is likely the linchpin in this part of the block I/O cgroup framework. It's the place where the connection between a kernel thread's I/O behavior and the control enforced by cgroups is established.
14/2	2026/10/26 20:24	tool	grepper	0m Args: { "Expression": "kthread_associate_blkcg" } Results: { "Output": "drivers/block/loop.c=1814=static void loop_handle_cmd(struct loop_cmd cmd)\n--\ndrivers/block/loop.c-1833-\tif (cmd_blkcg_css)\ndrivers/block/loop.c:1834:\t\tkthread_associate_blkcg(cmd_blkcg_css);\ndrivers/block/loop.c-1835-\tif (cmd_memcg_css)\n--\ndrivers/block/loop.c-1847-\tif (cmd_blkcg_css)\ndrivers/block/loop.c:1848:\t\tkthread_associate_blkcg(NULL);\ndrivers/block/loop.c-1849-\n--\ndrivers/nvme/target/core.c=544=bool nvmet_blkcg_begin(struct nvmet_req req)\n--\ndrivers/nvme/target/core.c-553-\tcss = cgroup_get_e_css(ns-\u003ecgrp, \u0026io_cgrp_subsys);\ndrivers/nvme/target/core.c:554:\tkthread_associate_blkcg(css);\ndrivers/nvme/target/core.c-555-\tcss_put(css);\n--\ndrivers/nvme/target/core.c=559=void nvmet_blkcg_end(bool associated)\n--\ndrivers/nvme/target/core.c-561-\tif (associated)\ndrivers/nvme/target/core.c:562:\t\tkthread_associate_blkcg(NULL);\ndrivers/nvme/target/core.c-563-}\n--\nfs/btrfs/inode.c=1032=static void submit_one_async_extent(struct async_chunk async_chunk,\n--\nfs/btrfs/inode.c-1051-\tif (async_chunk-\u003eblkcg_css)\nfs/btrfs/inode.c:1052:\t\tkthread_associate_blkcg(async_chunk-\u003eblkcg_css);\nfs/btrfs/inode.c-1053-\n--\nfs/btrfs/inode.c-1127-\tif (async_chunk-\u003eblkcg_css)\nfs/btrfs/inode.c:1128:\t\tkthread_associate_blkcg(NULL);\nfs/btrfs/inode.c-1129-\tkfree(async_extent);\n--\nfs/btrfs/inode.c-1145-\tif (async_chunk-\u003eblkcg_css)\nfs/btrfs/inode.c:1146:\t\tkthread_associate_blkcg(NULL);\nfs/btrfs/inode.c-1147-\tbtrfs_debug(fs_info,\n--\ninclude/linux/kthread.h=285=struct cgroup_subsys_state;\n--\ninclude/linux/kthread.h-287-#ifdef CONFIG_BLK_CGROUP\ninclude/linux/kthread.h:288:void kthread_associate_blkcg(struct cgroup_subsys_state css);\ninclude/linux/kthread.h-289-struct cgroup_subsys_state kthread_blkcg(void);\ninclude/linux/kthread.h-290-#else\ninclude/linux/kthread.h:291:static inline void kthread_associate_blkcg(struct cgroup_subsys_state css) { }\ninclude/linux/kthread.h-292-#endif\n--\nkernel/kthread.c=1688=EXPORT_SYMBOL_GPL(kthread_unuse_mm);\n--\nkernel/kthread.c-1691-/*\nkernel/kthread.c:1692: kthread_associate_blkcg - associate blkcg to current kthread\nkernel/kthread.c-1693- * @css: the cgroup info\n--\nkernel/kthread.c-1700- /\nkernel/kthread.c:1701:void kthread_associate_blkcg(struct cgroup_subsys_state css)\nkernel/kthread.c-1702-{\n--\nkernel/kthread.c-1719-}\nkernel/kthread.c:1720:EXPORT_SYMBOL(kthread_associate_blkcg);\nkernel/kthread.c-1721-\n" }
15/2	2026/10/26 20:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18953 output: 43 thoughts: 539 Thoughts: Analyzing Block CGroups in the NVMe-oF Subsystem Alright, let's dive into this `kthread_associate_blkcg` function. Seems straightforward enough – it's explicitly designed to run within the context of a kthread. That aligns perfectly with workqueue workers, as those are, in fact, kthreads. So, using it within work items launched on workqueues is valid. Okay, got that. This patch, though, highlights a web of asynchronous queuing, workqueues, and lifecycle management – cgroup references, destruction of workqueues, queuing requests, `memalloc_noio_save`, aborting dying queues... it's quite involved. Now, let's turn our attention to `nvmet_blkcg_work`. Here's the code: ```c static void nvmet_blkcg_work(struct work_struct work) { struct nvmet_req req = container_of(work, struct nvmet_req, blkcg_work); unsigned int noio_flag; bool associated; /* its queue is being deleted: abort it rather than throttle it / if (unlikely(percpu_ref_is_dying(&req->sq->ref))) { nvmet_req_complete(req, NVME_SC_ABORT_QUEUE); return; } / reclaim must not wait for I/O queued on this workqueue / noio_flag = memalloc_noio_save(); associated = nvmet_blkcg_begin(req); req->blkcg_execute(req); nvmet_blkcg_end(associated); memalloc_noio_restore(noio_flag); } ``` The key part appears to be how it handles the queue being deleted – it aborts the request. Also, the `memalloc_noio_save` and `restore` calls. The `blkcg_begin`, `req->blkcg_execute(req)`, and `blkcg_end` pattern seems central to the block cgroup interaction. Next, I need to check `nvmet_blkcg_init_req`: ```c static void nvmet_blkcg_init_req(struct nvmet_req req) { if (!req->ns->cgrp) return; req->blkcg_execute = req->execute; req->execute = nvmet_blkcg_queue_req; } ``` Interesting. It conditionally alters `req->execute`, likely to insert a block cgroup-related handler. But where is `nvmet_blkcg_init_req` actually called? Let's trace it down. Okay, found it. It's called within `nvmet_parse_io_cmd`: ```c static u16 nvmet_parse_io_cmd(struct nvmet_req req) { ... if (ret) return ret; nvmet_blkcg_init_req(req); if (req->ns->pr.enable) { ... ``` Aha! So, it’s being invoked after the command parsing phase. We're modifying the request execution path after* successfully parsing the I/O command. This changes how I need to think about this. It's important to understand what commands can be parsed here in the first place, now. So I should probably check that the `nvmet_parse_io_cmd` function as well.
16/2	2026/10/26 20:25	tool	grepper	0m Args: { "Expression": "static u16 nvmet_parse_io_cmd", "PathPrefixes": [ "drivers/nvme/target/core.c" ] } Results: { "Output": "drivers/nvme/target/core.c=1226=static u32 nvmet_io_cmd_transfer_len(struct nvmet_req req)\n--\ndrivers/nvme/target/core.c-1252-\ndrivers/nvme/target/core.c:1253:static u16 nvmet_parse_io_cmd(struct nvmet_req req)\ndrivers/nvme/target/core.c-1254-{\n" }
17/2	2026/10/26 20:25	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 20447 output: 39 thoughts: 27 Thoughts: Here's a breakdown of my thought process: Diving into the NVMe Target Command Parser Okay, time to get into the weeds. I need to understand how the NVMe target driver processes incoming I/O commands. The logical starting point seems to be `nvmet_parse_io_cmd` within the `drivers/nvme/target/core.c` file. I'm assuming this function is the central point where the raw command from the host is interpreted and broken down into something the target can actually work with. I expect to find the logic for handling different opcodes, figuring out the LBA, transfer length, and any other relevant command-specific parameters. This is where the magic happens, so to speak, where the NVMe specification gets translated into actionable instructions for the underlying storage. Knowing this is critical to understanding the entire flow. This is going to be my key focus.
18/2	2026/10/26 20:25	tool	read-file	0m Args: { "File": "drivers/nvme/target/core.c", "FirstLine": 1253, "LineCount": 65 } Results: { "Contents": "1253:\tstatic u16 nvmet_parse_io_cmd(struct nvmet_req req)\n1254:\t{\n1255:\t\tstruct nvme_command cmd = req-\u003ecmd;\n1256:\t\tu16 ret;\n1257:\t\n1258:\t\tif (nvme_is_fabrics(cmd))\n1259:\t\t\treturn nvmet_parse_fabrics_io_cmd(req);\n1260:\t\n1261:\t\tif (unlikely(!nvmet_check_auth_status(req)))\n1262:\t\t\treturn NVME_SC_AUTH_REQUIRED \| NVME_STATUS_DNR;\n1263:\t\n1264:\t\tret = nvmet_check_ctrl_status(req);\n1265:\t\tif (unlikely(ret))\n1266:\t\t\treturn ret;\n1267:\t\n1268:\t\tif (nvmet_is_passthru_req(req))\n1269:\t\t\treturn nvmet_parse_passthru_io_cmd(req);\n1270:\t\n1271:\t\tret = nvmet_req_find_ns(req);\n1272:\t\tif (unlikely(ret))\n1273:\t\t\treturn ret;\n1274:\t\n1275:\t\tret = nvmet_check_ana_state(req-\u003eport, req-\u003ens);\n1276:\t\tif (unlikely(ret)) {\n1277:\t\t\treq-\u003eerror_loc = offsetof(struct nvme_common_command, nsid);\n1278:\t\t\treturn ret;\n1279:\t\t}\n1280:\t\tret = nvmet_io_cmd_check_access(req);\n1281:\t\tif (unlikely(ret)) {\n1282:\t\t\treq-\u003eerror_loc = offsetof(struct nvme_common_command, nsid);\n1283:\t\t\treturn ret;\n1284:\t\t}\n1285:\t\n1286:\t\tif (req-\u003ens-\u003epr.enable) {\n1287:\t\t\tret = nvmet_parse_pr_cmd(req);\n1288:\t\t\tif (!ret)\n1289:\t\t\t\treturn ret;\n1290:\t\t}\n1291:\t\n1292:\t\tswitch (req-\u003ens-\u003ecsi) {\n1293:\t\tcase NVME_CSI_NVM:\n1294:\t\t\tif (req-\u003ens-\u003efile)\n1295:\t\t\t\tret = nvmet_file_parse_io_cmd(req);\n1296:\t\t\telse\n1297:\t\t\t\tret = nvmet_bdev_parse_io_cmd(req);\n1298:\t\t\tbreak;\n1299:\t\tcase NVME_CSI_ZNS:\n1300:\t\t\tif (IS_ENABLED(CONFIG_BLK_DEV_ZONED))\n1301:\t\t\t\tret = nvmet_bdev_zns_parse_io_cmd(req);\n1302:\t\t\telse\n1303:\t\t\t\tret = NVME_SC_INVALID_IO_CMD_SET;\n1304:\t\t\tbreak;\n1305:\t\tdefault:\n1306:\t\t\tret = NVME_SC_INVALID_IO_CMD_SET;\n1307:\t\t}\n1308:\t\tif (ret)\n1309:\t\t\treturn ret;\n1310:\t\n1311:\t\tnvmet_blkcg_init_req(req);\n1312:\t\n1313:\t\tif (req-\u003ens-\u003epr.enable) {\n1314:\t\t\tret = nvmet_pr_check_cmd_access(req);\n1315:\t\t\tif (ret)\n1316:\t\t\t\treturn ret;\n1317:\t\n" }
19/2	2026/10/26 20:25	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21672 output: 30 thoughts: 1035 Thoughts: Reaching and Fuzzing NVMe Block CGroups Integration Okay, let's break this down. My goal is to determine if this new `nvmet_blkcg_` logic is reachable and fuzz-able. Starting with the code itself, I see that the `nvmet_parse_io_cmd` function is key. It dispatches to either `nvmet_bdev_parse_io_cmd` or `nvmet_file_parse_io_cmd`, setting up the `req->execute` function pointer. Then, `nvmet_blkcg_init_req(req)` cleverly wraps that execution, essentially intercepting and rerouting it. Now, instead of the original `req->execute`, we're going through `nvmet_blkcg_queue_req(req)`. This queues the work on `req->ns->blkcg_wq`. And when the work finally executes, it associates with the blkcg. Crucially, even functions like `nvmet_file_execute_flush` that spawn async work also end up going through `req->ns->blkcg_wq` via `nvmet_req_queue_work`. This dance of workqueues, associations, and disassociations really screams potential concurrency bugs. So, the question is, can* this code actually be executed? The triage philosophy is clear: reachability is paramount. If I can't trigger this code path in a standard, virtualized environment, it's a non-starter. The good news is, NVMe targets can indeed run in QEMU! I can use either `CONFIG_NVME_TARGET_LOOP` (loopback) or `CONFIG_NVME_TARGET_TCP` (TCP over `lo`). These are purely software drivers, making them perfect for my fuzzing needs. I can also mount configfs and manipulate `/config/nvmet/...` which means cgroups (v2), which are standard in modern Linux setups, will be accessible. The new `cgroup_id` attribute will allow me to configure a cgroup ID for a namespace. Once configured, all incoming I/O will hit the new `nvmet_blkcg_` logic. This sets up the potential for concurrency issues and race conditions. Think about namespace enable/disable, queue aborts, possible use-after-free or refcount problems. Given all this, I'm confident that this code is* reachable and absolutely worth fuzzing. `WorthFuzzing = true`. Now, let's confirm the necessary kernel configurations. I need to make sure I understand the dependencies. The patch itself is wrapped with `#ifdef CONFIG_BLK_CGROUP`. Good. And I know I need `CONFIG_NVME_TARGET` for NVMe target support. Looking at the Kconfig file, `NVME_TARGET` depends on `BLOCK` and selects `CONFIGFS_FS`. To interact with `nvmet`, I need either `NVME_TARGET_LOOP` (or does `NVME_LOOP` get involved on the host side?) or `NVME_TARGET_TCP`.
20/2	2026/10/26 20:25	tool	grepper	0m Args: { "Expression": "NVME_TARGET", "PathPrefixes": [ "drivers/nvme/" ] } Results: { "Output": "\nFull output is too long, showing 200 out of 389 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (14 files in total):\ndrivers/nvme/host/core.c:7\ndrivers/nvme/host/fc.c:1\ndrivers/nvme/target/Kconfig:28\ndrivers/nvme/target/Makefile:10\ndrivers/nvme/target/auth.c:7\ndrivers/nvme/target/configfs.c:11\ndrivers/nvme/target/core.c:1\ndrivers/nvme/target/debugfs.c:2\ndrivers/nvme/target/debugfs.h:1\ndrivers/nvme/target/fabrics-cmd-auth.c:1\ndrivers/nvme/target/fabrics-cmd.c:4\ndrivers/nvme/target/nvmet.h:14\ndrivers/nvme/target/passthru.c:1\ndrivers/nvme/target/tcp.c:3\n\ndrivers/nvme/host/core.c=731=void nvme_put_ns(struct nvme_ns ns)\n--\ndrivers/nvme/host/core.c-734-}\ndrivers/nvme/host/core.c:735:EXPORT_SYMBOL_NS_GPL(nvme_put_ns, \"NVME_TARGET_PASSTHRU\");\ndrivers/nvme/host/core.c-736-\n--\ndrivers/nvme/host/core.c=1168=int nvme_execute_rq(struct request rq, bool at_head)\n--\ndrivers/nvme/host/core.c-1178-}\ndrivers/nvme/host/core.c:1179:EXPORT_SYMBOL_NS_GPL(nvme_execute_rq, \"NVME_TARGET_PASSTHRU\");\ndrivers/nvme/host/core.c-1180-\n--\ndrivers/nvme/host/core.c=1232=u32 nvme_command_effects(struct nvme_ctrl ctrl, struct nvme_ns ns, u8 opcode)\n--\ndrivers/nvme/host/core.c-1258-}\ndrivers/nvme/host/core.c:1259:EXPORT_SYMBOL_NS_GPL(nvme_command_effects, \"NVME_TARGET_PASSTHRU\");\ndrivers/nvme/host/core.c-1260-\ndrivers/nvme/host/core.c=1261=u32 nvme_passthru_start(struct nvme_ctrl ctrl, struct nvme_ns ns, u8 opcode)\n--\ndrivers/nvme/host/core.c-1278-}\ndrivers/nvme/host/core.c:1279:EXPORT_SYMBOL_NS_GPL(nvme_passthru_start, \"NVME_TARGET_PASSTHRU\");\ndrivers/nvme/host/core.c-1280-\ndrivers/nvme/host/core.c=1281=u32 nvme_passthru_end(struct nvme_ctrl ctrl, struct nvme_ns ns, u32 effects,\n--\ndrivers/nvme/host/core.c-1325-}\ndrivers/nvme/host/core.c:1326:EXPORT_SYMBOL_NS_GPL(nvme_passthru_end, \"NVME_TARGET_PASSTHRU\");\ndrivers/nvme/host/core.c-1327-\n--\ndrivers/nvme/host/core.c=4235=struct nvme_ns nvme_find_get_ns(struct nvme_ctrl ctrl, unsigned nsid)\n--\ndrivers/nvme/host/core.c-4254-}\ndrivers/nvme/host/core.c:4255:EXPORT_SYMBOL_NS_GPL(nvme_find_get_ns, \"NVME_TARGET_PASSTHRU\");\ndrivers/nvme/host/core.c-4256-\n--\ndrivers/nvme/host/core.c=5480=struct nvme_ctrl nvme_ctrl_from_file(struct file file)\n--\ndrivers/nvme/host/core.c-5485-}\ndrivers/nvme/host/core.c:5486:EXPORT_SYMBOL_NS_GPL(nvme_ctrl_from_file, \"NVME_TARGET_PASSTHRU\");\ndrivers/nvme/host/core.c-5487-\n--\ndrivers/nvme/host/fc.c=3447=nvme_fc_alloc_ctrl(struct device dev, struct nvmf_ctrl_options opts,\n--\ndrivers/nvme/host/fc.c-3453-\tif (!(rport-\u003eremoteport.port_role \u0026\ndrivers/nvme/host/fc.c:3454:\t (FC_PORT_ROLE_NVME_DISCOVERY \| FC_PORT_ROLE_NVME_TARGET))) {\ndrivers/nvme/host/fc.c-3455-\t\tret = -EBADR;\n--\ndrivers/nvme/target/Kconfig-2-\ndrivers/nvme/target/Kconfig:3:config NVME_TARGET\ndrivers/nvme/target/Kconfig-4-\ttristate \"NVMe Target support\"\n--\ndrivers/nvme/target/Kconfig-6-\tselect CONFIGFS_FS\ndrivers/nvme/target/Kconfig:7:\tselect NVME_KEYRING if NVME_TARGET_TCP_TLS\ndrivers/nvme/target/Kconfig:8:\tselect KEYS if NVME_TARGET_TCP_TLS\ndrivers/nvme/target/Kconfig-9-\tselect SGL_ALLOC\n--\ndrivers/nvme/target/Kconfig-19-\ndrivers/nvme/target/Kconfig:20:config NVME_TARGET_DEBUGFS\ndrivers/nvme/target/Kconfig-21- bool \"NVMe Target debugfs support\"\ndrivers/nvme/target/Kconfig:22:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig-23-\thelp\n--\ndrivers/nvme/target/Kconfig-28-\ndrivers/nvme/target/Kconfig:29:config NVME_TARGET_PASSTHRU\ndrivers/nvme/target/Kconfig-30-\tbool \"NVMe Target Passthrough support\"\ndrivers/nvme/target/Kconfig:31:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig:32:\tdepends on NVME_CORE=y \|\| NVME_CORE=NVME_TARGET\ndrivers/nvme/target/Kconfig-33-\thelp\n--\ndrivers/nvme/target/Kconfig-40-\ndrivers/nvme/target/Kconfig:41:config NVME_TARGET_LOOP\ndrivers/nvme/target/Kconfig-42-\ttristate \"NVMe loopback device support\"\ndrivers/nvme/target/Kconfig:43:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig-44-\tselect NVME_FABRICS\n--\ndrivers/nvme/target/Kconfig-51-\ndrivers/nvme/target/Kconfig:52:config NVME_TARGET_RDMA\ndrivers/nvme/target/Kconfig-53-\ttristate \"NVMe over Fabrics RDMA target support\"\ndrivers/nvme/target/Kconfig-54-\tdepends on INFINIBAND \u0026\u0026 INFINIBAND_ADDR_TRANS\ndrivers/nvme/target/Kconfig:55:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig-56-\tselect SGL_ALLOC\n--\ndrivers/nvme/target/Kconfig-62-\ndrivers/nvme/target/Kconfig:63:config NVME_TARGET_FC\ndrivers/nvme/target/Kconfig-64-\ttristate \"NVMe over Fabrics FC target driver\"\ndrivers/nvme/target/Kconfig:65:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig-66-\tdepends on HAS_DMA\n--\ndrivers/nvme/target/Kconfig-73-\ndrivers/nvme/target/Kconfig:74:config NVME_TARGET_FCLOOP\ndrivers/nvme/target/Kconfig-75-\ttristate \"NVMe over Fabrics FC Transport Loopback Test driver\"\ndrivers/nvme/target/Kconfig:76:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig-77-\tselect NVME_FABRICS\n--\ndrivers/nvme/target/Kconfig-79-\tdepends on NVME_FC\ndrivers/nvme/target/Kconfig:80:\tdepends on NVME_TARGET_FC\ndrivers/nvme/target/Kconfig-81-\thelp\n--\ndrivers/nvme/target/Kconfig-86-\ndrivers/nvme/target/Kconfig:87:config NVME_TARGET_TCP\ndrivers/nvme/target/Kconfig-88-\ttristate \"NVMe over Fabrics TCP target support\"\ndrivers/nvme/target/Kconfig-89-\tdepends on INET\ndrivers/nvme/target/Kconfig:90:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig-91-\thelp\n--\ndrivers/nvme/target/Kconfig-96-\ndrivers/nvme/target/Kconfig:97:config NVME_TARGET_TCP_TLS\ndrivers/nvme/target/Kconfig-98-\tbool \"NVMe over Fabrics TCP target TLS encryption support\"\ndrivers/nvme/target/Kconfig:99:\tdepends on NVME_TARGET_TCP\ndrivers/nvme/target/Kconfig-100-\tselect NET_HANDSHAKE\n--\ndrivers/nvme/target/Kconfig-109-\ndrivers/nvme/target/Kconfig:110:config NVME_TARGET_AUTH\ndrivers/nvme/target/Kconfig-111-\tbool \"NVMe over Fabrics In-band Authentication in target side\"\ndrivers/nvme/target/Kconfig:112:\tdepends on NVME_TARGET\ndrivers/nvme/target/Kconfig-113-\tselect NVME_AUTH\n--\ndrivers/nvme/target/Kconfig-119-\ndrivers/nvme/target/Kconfig:120:config NVME_TARGET_AUTH_DEBUG\ndrivers/nvme/target/Kconfig-121-\tbool \"NVMe over Fabrics In-band Authentication debug messages\"\ndrivers/nvme/target/Kconfig:122:\tdepends on NVME_TARGET_AUTH\ndrivers/nvme/target/Kconfig-123-\thelp\n--\ndrivers/nvme/target/Kconfig-128-\ndrivers/nvme/target/Kconfig:129:config NVME_TARGET_PCI_EPF\ndrivers/nvme/target/Kconfig-130-\ttristate \"NVMe PCI Endpoint Function target support\"\ndrivers/nvme/target/Kconfig:131:\tdepends on NVME_TARGET \u0026\u0026 PCI_ENDPOINT\ndrivers/nvme/target/Kconfig:132:\tdepends on NVME_CORE=y \|\| NVME_CORE=NVME_TARGET\ndrivers/nvme/target/Kconfig-133-\thelp\n--\ndrivers/nvme/target/Makefile=3=ccflags-y\t\t\t\t+= -I$(src)\ndrivers/nvme/target/Makefile-4-\ndrivers/nvme/target/Makefile:5:obj-$(CONFIG_NVME_TARGET)\t\t+= nvmet.o\ndrivers/nvme/target/Makefile:6:obj-$(CONFIG_NVME_TARGET_LOOP)\t\t+= nvme-loop.o\ndrivers/nvme/target/Makefile:7:obj-$(CONFIG_NVME_TARGET_RDMA)\t\t+= nvmet-rdma.o\ndrivers/nvme/target/Makefile:8:obj-$(CONFIG_NVME_TARGET_FC)\t\t+= nvmet-fc.o\ndrivers/nvme/target/Makefile:9:obj-$(CONFIG_NVME_TARGET_FCLOOP)\t+= nvme-fcloop.o\ndrivers/nvme/target/Makefile:10:obj-$(CONFIG_NVME_TARGET_TCP)\t\t+= nvmet-tcp.o\ndrivers/nvme/target/Makefile:11:obj-$(CONFIG_NVME_TARGET_PCI_EPF)\t+= nvmet-pci-epf.o\ndrivers/nvme/target/Makefile-12-\ndrivers/nvme/target/Makefile=13=nvmet-y\t\t+= core.o configfs.o admin-cmd.o fabrics-cmd.o \\\ndrivers/nvme/target/Makefile-14-\t\t\tdiscovery.o io-cmd-file.o io-cmd-bdev.o pr.o\ndrivers/nvme/target/Makefile:15:nvmet-$(CONFIG_NVME_TARGET_DEBUGFS)\t+= debugfs.o\ndrivers/nvme/target/Makefile:16:nvmet-$(CONFIG_NVME_TARGET_PASSTHRU)\t+= passthru.o\ndrivers/nvme/target/Makefile-17-nvmet-$(CONFIG_BLK_DEV_ZONED)\t\t+= zns.o\ndrivers/nvme/target/Makefile:18:nvmet-$(CONFIG_NVME_TARGET_AUTH)\t+= fabrics-cmd-auth.o auth.o\ndrivers/nvme/target/Makefile-19-nvme-loop-y\t+= loop.o\n--\ndrivers/nvme/target/auth.c=133=u8 nvmet_setup_auth(struct nvmet_ctrl ctrl, struct nvmet_sq sq, bool reset)\n--\ndrivers/nvme/target/auth.c-190-\t}\ndrivers/nvme/target/auth.c:191:#ifdef CONFIG_NVME_TARGET_AUTH_DEBUG\ndrivers/nvme/target/auth.c-192-\tpr_debug(\"%s: using hash %s key %ph\\n\", __func__,\n--\ndrivers/nvme/target/auth.c-209-\t}\ndrivers/nvme/target/auth.c:210:#ifdef CONFIG_NVME_TARGET_AUTH_DEBUG\ndrivers/nvme/target/auth.c-211-\tpr_debug(\"%s: using ctrl hash %s key %ph\\n\", __func__,\n--\ndrivers/nvme/target/auth.c=248=void nvmet_destroy_auth(struct nvmet_ctrl ctrl)\n--\ndrivers/nvme/target/auth.c-267-\t}\ndrivers/nvme/target/auth.c:268:#ifdef CONFIG_NVME_TARGET_TCP_TLS\ndrivers/nvme/target/auth.c-269-\tif (ctrl-\u003etls_key) {\n--\ndrivers/nvme/target/auth.c=428=int nvmet_auth_ctrl_exponential(struct nvmet_req req,\n--\ndrivers/nvme/target/auth.c-443-\t\tmemcpy(buf, ctrl-\u003edh_key, buf_size);\ndrivers/nvme/target/auth.c:444:#ifdef CONFIG_NVME_TARGET_AUTH_DEBUG\ndrivers/nvme/target/auth.c-445-\t\tpr_debug(\"%s: ctrl %d public key %ph\\n\", __func__,\n--\ndrivers/nvme/target/auth.c=453=int nvmet_auth_ctrl_sesskey(struct nvmet_req req,\n--\ndrivers/nvme/target/auth.c-469-\t\tpr_debug(\"failed to compute session key, err %d\\n\", ret);\ndrivers/nvme/target/auth.c:470:#ifdef CONFIG_NVME_TARGET_AUTH_DEBUG\ndrivers/nvme/target/auth.c-471-\telse\n--\ndrivers/nvme/target/auth.c=479=void nvmet_auth_insert_psk(struct nvmet_sq sq)\n--\ndrivers/nvme/target/auth.c-485-\tint ret;\ndrivers/nvme/target/auth.c:486:#ifdef CONFIG_NVME_TARGET_TCP_TLS\ndrivers/nvme/target/auth.c-487-\tstruct key tls_key = NULL;\n--\ndrivers/nvme/target/auth.c-514-\t}\ndrivers/nvme/target/auth.c:515:#ifdef CONFIG_NVME_TARGET_TCP_TLS\ndrivers/nvme/target/auth.c-516-\ttls_key = nvme_tls_psk_refresh(NULL, sq-\u003ectrl-\u003ehostnqn,\n--\ndrivers/nvme/target/configfs.c-15-#include \u003clinux/pci-p2pdma.h\u003e\ndrivers/nvme/target/configfs.c:16:#ifdef CONFIG_NVME_TARGET_AUTH\ndrivers/nvme/target/configfs.c-17-#include \u003clinux/nvme-auth.h\u003e\n--\ndrivers/nvme/target/configfs.c=467=static ssize_t nvmet_addr_tsas_store(struct config_item *item,\n--\ndrivers/nvme/target/configfs.c-491-\tif (sectype == NVMF_TCP_SECTYPE_TLS13) {\ndrivers/nvme/target/configfs.c:492:\t\tif (!IS_ENABLED(CONFIG_NVME_TARGET_TCP_TLS)) {\ndrivers/nvme/target/configfs.c-493-\t\t\tpr_err(\"TLS is not supported\\n\");\n--\ndrivers/nvme/target/configfs.c=944=static const struct config_item_type nvmet_namespaces_type = {\n--\ndrivers/nvme/target/configfs.c-948-\ndrivers/nvme/target/configfs.c:949:#ifdef CONFIG_NVME_TARGET_PASSTHRU\ndrivers/nvme/target/configfs.c-950-\n\n" }
21/2	2026/10/26 20:25	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27792 output: 276 thoughts: 2373 Thoughts: Analysis of NVMe Target Cgroup v2 Support Patch for Fuzzing Alright, let's break down this patch and determine the optimal fuzzing strategy. First, I see the core of the change revolves around cgroup v2 integration for NVMe target namespaces within the kernel, specifically targeting the `drivers/nvme/target` directory. Looking at the `Makefile`, it's clear that this code is conditionally compiled when `CONFIG_NVME_TARGET` is enabled, and the cgroup-related bits hinge on `CONFIG_BLK_CGROUP`. Additionally, enabling either `NVME_TARGET_LOOP` or `NVME_TARGET_TCP` (along with their core dependencies) will be important to actually test I/O commands. And the zone changes require `CONFIG_BLK_DEV_ZONED`. The fundamental configuration requirements appear to be: `NVME_TARGET`, `BLK_CGROUP`, and optionally `NVME_TARGET_LOOP` (or `NVME_TARGET_TCP`). The selection of `CONFIGFS_FS` is also implicit due to `NVME_TARGET`. `BLK_DEV_ZONED` is also important for the changes in `zns.c`. Now, let's identify the key functions that are altered or added by the patch. I'll need to use these as "FocusSymbols". The goal here is to point the fuzzer at the new, feature-specific logic. I need to avoid ubiquitous functions, so general memory allocators or synchronization primitives are out. I must focus on the entry points or altered logic. Here’s the breakdown: * From `drivers/nvme/target/configfs.c`: `nvmet_ns_cgroup_id_show`, `nvmet_ns_cgroup_id_store` (configfs attribute handlers, `nvmet_ns_attr_cgroup_id`). * From `drivers/nvme/target/core.c`: `nvmet_blkcg_ns_enable`, `nvmet_blkcg_ns_disable`, `nvmet_blkcg_begin`, `nvmet_blkcg_end`, `nvmet_blkcg_work`, `nvmet_blkcg_queue_req`, `nvmet_blkcg_init_req`, `nvmet_ns_enable`, `nvmet_ns_dev_disable`, `nvmet_parse_io_cmd`. * From `drivers/nvme/target/io-cmd-file.c`: `nvmet_file_flush_work`, `nvmet_file_execute_flush`, `nvmet_file_execute_discard`, `nvmet_file_execute_dsm`, `nvmet_file_write_zeroes_work`, `nvmet_file_execute_write_zeroes`. * From `drivers/nvme/target/nvmet.h`: `nvmet_req_queue_work`. * From `drivers/nvme/target/zns.c`: `nvmet_bdev_zmgmt_send_work`, `nvmet_bdev_execute_zone_mgmt_send`. Now, let's identify which of these are good "FocusSymbols". Static inline functions are usually not helpful, but non-static and those with symbols are. The non-static functions are ideal entry points. So, I will focus on the ones that specifically implement the cgroup logic: * `nvmet_ns_cgroup_id_store` * `nvmet_blkcg_ns_enable` * `nvmet_blkcg_ns_disable` * `nvmet_blkcg_begin` * `nvmet_blkcg_end` * `nvmet_blkcg_work` * `nvmet_ns_enable` I will add other functions that directly call the blkcg logic as well. Considering this patch is all about a new feature (cgroup integration) introducing asynchronous paths (workqueues), refcounting, and lifecycle management within the NVMe target, the `WorthFuzzing` flag is definitely `true`. Testing will be easy because this can all be done in a virtualized environment. The new code is also reachable without needing any special hardware. My final arguments for the `set-results` command are: * `WorthFuzzing`: true * `Reasoning`: Introduces cgroup v2 support for NVMe target namespaces, adds new execution paths, refcounting, and lifecycle management, all of which are suitable for fuzzing in a virtualized environment. * `FocusSymbols`: `nvmet_ns_cgroup_id_store`, `nvmet_blkcg_ns_
22/2	2026/10/26 20:25	tool	set-results	0m Args: { "EnableConfigs": [ "NVME_TARGET", "BLK_CGROUP", "NVME_TARGET_LOOP", "CONFIGFS_FS" ], "FocusSymbols": [ "nvmet_ns_cgroup_id_store", "nvmet_blkcg_ns_enable", "nvmet_blkcg_ns_disable", "nvmet_blkcg_begin", "nvmet_blkcg_end", "nvmet_blkcg_work", "nvmet_ns_enable" ], "Reasoning": "The patch introduces cgroup v2 throttling and charging support for NVMe target (nvmet) namespaces. When a namespace is configured with a cgroup_id via configfs, I/O commands are dispatched through a dedicated per-namespace workqueue and associated with the cgroup's blkcg css via kthread_associate_blkcg. This code is fully reachable in standard virtualized QEMU environments using virtual/loopback transports (such as nvme-loop or nvmet-tcp over loopback). The changes add concurrency, asynchronous workqueue handling, cgroup refcounting, and teardown synchronization, which warrants fuzzing to detect potential race conditions or resource leaks.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "NVME_TARGET", "BLK_CGROUP", "NVME_TARGET_LOOP", "CONFIGFS_FS" ], "FocusSymbols": [ "nvmet_ns_cgroup_id_store", "nvmet_blkcg_ns_enable", "nvmet_blkcg_ns_disable", "nvmet_blkcg_begin", "nvmet_blkcg_end", "nvmet_blkcg_work", "nvmet_ns_enable" ], "Reasoning": "The patch introduces cgroup v2 throttling and charging support for NVMe target (nvmet) namespaces. When a namespace is configured with a cgroup_id via configfs, I/O commands are dispatched through a dedicated per-namespace workqueue and associated with the cgroup's blkcg css via kthread_associate_blkcg. This code is fully reachable in standard virtualized QEMU environments using virtual/loopback transports (such as nvme-loop or nvmet-tcp over loopback). The changes add concurrency, asynchronous workqueue handling, cgroup refcounting, and teardown synchronization, which warrants fuzzing to detect potential race conditions or resource leaks.", "WorthFuzzing": true }
23/1	2026/10/26 20:25	action	If	1m Args: { "WorthFuzzing": true } Results: null
24/2	2026/10/26 20:25	agent	kmsan-evaluator	1m Model: core Args: null Results: { "KMSANReasoning": "The patch adds cgroup-based I/O throttling support to NVMe target (nvmet) namespaces via configfs (`cgroup_id` attribute), dispatching I/O requests through dedicated per-namespace workqueues associated with the corresponding blkcg.\n\nFrom a memory safety perspective:\n1. All newly introduced struct members in `struct nvmet_ns` (`cgroup_id`, `cgrp`, `blkcg_wq`) are zero-initialized at allocation time via `kzalloc_obj()` in `nvmet_ns_alloc()`.\n2. The new configfs attribute show handler (`nvmet_ns_cgroup_id_show`) formats a scalar `u64` into an ASCII string using `snprintf()`, presenting no uninitialized padding or info-leak risk.\n3. In `nvmet_req`, the new fields (`blkcg_execute`, `blkcg_work`) are initialized via `INIT_WORK` and direct assignment during request handling when `ns-\u003ecgrp` is active, and local variables (`associated`, `status`, `noio_flag`) are explicitly assigned before use.\n4. Any potential issues with this patch relate to concurrency, lifetime management of the workqueue/cgroup reference across disable/enable operations, use-after-free, or locking dependencies, all of which are covered by KASAN and LOCKDEP.\n\nThere are no uninitialized memory reads or kernel info-leaks, so a dedicated KMSAN session is not warranted.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 21158167c09894da68b4c04b907acbadceeeed2a Author: syz-cluster <triage@syzkaller.com> Date: Mon Oct 26 20:23:56 2026 +0000 syz-cluster: applied patch under review diff --git a/Documentation/ABI/stable/configfs-nvmet b/Documentation/ABI/stable/configfs-nvmet index 36b587404ee7ef..ea9c4083c6a0de 100644 --- a/Documentation/ABI/stable/configfs-nvmet +++ b/Documentation/ABI/stable/configfs-nvmet @@ -314,6 +314,22 @@ Description: attr_subsys_vendor_id: Shows or sets the PCI subsystem vendor ID. Displayed in "0x%x" format. +What: /config/nvmet/subsystems/NAME/namespaces/NSID/cgroup_id +Date: October 2026 +KernelVersion: 7.5 +Contact: Peng Yu <yupeng0921@gmail.com> +Description: + Shows or sets the cgroup2 ID of the cgroup to charge this + namespace's I/O to. Writing 0 clears it. The I/O is + charged to the cgroup's effective io css: the cgroup + itself or its nearest ancestor with the io controller + enabled. The namespace must be disabled before + modification. Enabling the namespace fails if the cgroup + can't be found or if buffered_io is set. A cgroup that is + removed and created again gets a new ID. + + Only available when CONFIG_BLK_CGROUP is enabled. + What: /config/nvmet/hosts/HOSTNQN/dhchap_key What: /config/nvmet/hosts/HOSTNQN/dhchap_ctrl_key What: /config/nvmet/hosts/HOSTNQN/dhchap_hash diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c index 8aea64d279c4af..9f0d48677c4a22 100644 --- a/drivers/nvme/target/configfs.c +++ b/drivers/nvme/target/configfs.c @@ -564,6 +564,50 @@ static ssize_t nvmet_ns_device_path_store(struct config_item item, CONFIGFS_ATTR(nvmet_ns_, device_path); +#ifdef CONFIG_BLK_CGROUP +static ssize_t nvmet_ns_cgroup_id_show(struct config_item item, char page) +{ + struct nvmet_ns ns = to_nvmet_ns(item); + struct nvmet_subsys subsys = ns->subsys; + ssize_t ret; + + mutex_lock(&subsys->lock); + ret = snprintf(page, PAGE_SIZE, "%llu\n", ns->cgroup_id); + mutex_unlock(&subsys->lock); + return ret; +} + +static ssize_t nvmet_ns_cgroup_id_store(struct config_item item, + const char page, size_t count) +{ + struct nvmet_ns ns = to_nvmet_ns(item); + struct nvmet_subsys subsys = ns->subsys; + u64 cgroup_id; + int ret; + + ret = kstrtou64(page, 0, &cgroup_id); + if (ret) + return ret; + + mutex_lock(&subsys->lock); + + if (ns->enabled) { + ret = -EBUSY; + goto out_unlock; + } + + / Writing 0 clears the association. / + ns->cgroup_id = cgroup_id; + ret = count; + +out_unlock: + mutex_unlock(&subsys->lock); + return ret; +} + +CONFIGFS_ATTR(nvmet_ns_, cgroup_id); +#endif / CONFIG_BLK_CGROUP / + #ifdef CONFIG_PCI_P2PDMA static ssize_t nvmet_ns_p2pmem_show(struct config_item item, char page) { @@ -836,6 +880,9 @@ static struct configfs_attribute nvmet_ns_attrs[] = { &nvmet_ns_attr_buffered_io, &nvmet_ns_attr_revalidate_size, &nvmet_ns_attr_resv_enable, +#ifdef CONFIG_BLK_CGROUP + &nvmet_ns_attr_cgroup_id, +#endif #ifdef CONFIG_PCI_P2PDMA &nvmet_ns_attr_p2pmem, #endif diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c index 8353950f346f3c..5472a8b3853ca8 100644 --- a/drivers/nvme/target/core.c +++ b/drivers/nvme/target/core.c @@ -4,12 +4,15 @@ * Copyright (c) 2015-2016 HGST, a Western Digital Company. / #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/cgroup.h> #include <linux/hex.h> +#include <linux/kthread.h> #include <linux/module.h> #include <linux/random.h> #include <linux/rculist.h> #include <linux/pci-p2pdma.h> #include <linux/scatterlist.h> +#include <linux/sched/mm.h> #include <generated/utsrelease.h> @@ -481,8 +484,144 @@ void nvmet_put_namespace(struct nvmet_ns ns) percpu_ref_put(&ns->ref); } +#ifdef CONFIG_BLK_CGROUP +static int nvmet_blkcg_ns_enable(struct nvmet_ns ns) +{ + struct cgroup cgrp; + + if (!ns->cgroup_id) + return 0; + + /* + * Buffered writes will be handled by a separate thread, + * these IOs have no namespace/cgroup information at that time, + * so we don't support buffered io. + / + if (ns->buffered_io) { + pr_err("cgroup_id is not supported with buffered_io: %s\n", + ns->device_path); + return -EINVAL; + } + + cgrp = cgroup_get_from_id(ns->cgroup_id); + if (IS_ERR(cgrp)) { + pr_err("failed to resolve cgroup id %llu: %ld\n", + ns->cgroup_id, PTR_ERR(cgrp)); + return PTR_ERR(cgrp); + } + + ns->blkcg_wq = alloc_workqueue("nvmet-blkcg-%u", + WQ_MEM_RECLAIM \| WQ_UNBOUND, num_online_cpus(), + ns->nsid); + if (!ns->blkcg_wq) { + cgroup_put(cgrp); + return -ENOMEM; + } + + ns->cgrp = cgrp; + return 0; +} + +static void nvmet_blkcg_ns_disable(struct nvmet_ns ns) +{ + if (ns->cgrp) { + /* + * No command is left, but the work item of a command that + * completed from inside ->blkcg_execute() may still be + * returning: destroy_workqueue() waits for it. + / + destroy_workqueue(ns->blkcg_wq); + ns->blkcg_wq = NULL; + cgroup_put(ns->cgrp); + ns->cgrp = NULL; + } +} + +/ + * Charge the I/O that the current work item submits for @req to the + * effective io css of the namespace's cgroup, looked up for each command. + / +bool nvmet_blkcg_begin(struct nvmet_req req) +{ + struct nvmet_ns ns = req->ns; + struct cgroup_subsys_state css; + + /* a disable waits for the command: don't throttle it any more / + if (!ns->cgrp \|\| !READ_ONCE(ns->enabled)) + return false; + + css = cgroup_get_e_css(ns->cgrp, &io_cgrp_subsys); + kthread_associate_blkcg(css); + css_put(css); + return true; +} + +void nvmet_blkcg_end(bool associated) +{ + if (associated) + kthread_associate_blkcg(NULL); +} + +/ + * The io.cost and io.latency enforce their limits by putting the thread to + * sleep. A transport thread may be shared by multiple namespaces. In the + * tcp-nvmeof case, all namespaces in the same subsystem may share a + * thread. So we submit the IOs via the workqueue, thus the current thread + * won't be blocked. + / +static void nvmet_blkcg_work(struct work_struct work) +{ + struct nvmet_req req = + container_of(work, struct nvmet_req, blkcg_work); + unsigned int noio_flag; + bool associated; + + / its queue is being deleted: abort it rather than throttle it / + if (unlikely(percpu_ref_is_dying(&req->sq->ref))) { + nvmet_req_complete(req, NVME_SC_ABORT_QUEUE); + return; + } + + / reclaim must not wait for I/O queued on this workqueue / + noio_flag = memalloc_noio_save(); + associated = nvmet_blkcg_begin(req); + req->blkcg_execute(req); + nvmet_blkcg_end(associated); + memalloc_noio_restore(noio_flag); +} + +static void nvmet_blkcg_queue_req(struct nvmet_req req) +{ + INIT_WORK(&req->blkcg_work, nvmet_blkcg_work); + queue_work(req->ns->blkcg_wq, &req->blkcg_work); +} + +static void nvmet_blkcg_init_req(struct nvmet_req req) +{ + if (!req->ns->cgrp) + return; + + req->blkcg_execute = req->execute; + req->execute = nvmet_blkcg_queue_req; +} +#else +static inline int nvmet_blkcg_ns_enable(struct nvmet_ns ns) +{ + return 0; +} + +static inline void nvmet_blkcg_ns_disable(struct nvmet_ns ns) +{ +} + +static inline void nvmet_blkcg_init_req(struct nvmet_req req) +{ +} +#endif /* CONFIG_BLK_CGROUP / + static void nvmet_ns_dev_disable(struct nvmet_ns ns) { + nvmet_blkcg_ns_disable(ns); nvmet_bdev_ns_disable(ns); nvmet_file_ns_disable(ns); } @@ -609,6 +748,10 @@ int nvmet_ns_enable(struct nvmet_ns ns) if (ret) goto out_unlock; + ret = nvmet_blkcg_ns_enable(ns); + if (ret) + goto out_dev_disable; + ret = nvmet_p2pmem_ns_enable(ns); if (ret) goto out_dev_disable; @@ -1165,6 +1308,8 @@ static u16 nvmet_parse_io_cmd(struct nvmet_req req) if (ret) return ret; + nvmet_blkcg_init_req(req); + if (req->ns->pr.enable) { ret = nvmet_pr_check_cmd_access(req); if (ret) diff --git a/drivers/nvme/target/io-cmd-file.c b/drivers/nvme/target/io-cmd-file.c index 695963dd932ee7..673df713c954f9 100644 --- a/drivers/nvme/target/io-cmd-file.c +++ b/drivers/nvme/target/io-cmd-file.c @@ -257,8 +257,13 @@ u16 nvmet_file_flush(struct nvmet_req req) static void nvmet_file_flush_work(struct work_struct w) { struct nvmet_req req = container_of(w, struct nvmet_req, f.work); + bool associated; + u16 status; - nvmet_req_complete(req, nvmet_file_flush(req)); + associated = nvmet_blkcg_begin(req); + status = nvmet_file_flush(req); + nvmet_blkcg_end(associated); + nvmet_req_complete(req, status); } static void nvmet_file_execute_flush(struct nvmet_req req) @@ -266,7 +271,7 @@ static void nvmet_file_execute_flush(struct nvmet_req req) if (!nvmet_check_transfer_len(req, 0)) return; INIT_WORK(&req->f.work, nvmet_file_flush_work); - queue_work(nvmet_wq, &req->f.work); + nvmet_req_queue_work(req, nvmet_wq, &req->f.work); } static void nvmet_file_execute_discard(struct nvmet_req req) @@ -274,10 +279,12 @@ static void nvmet_file_execute_discard(struct nvmet_req req) int mode = FALLOC_FL_PUNCH_HOLE \| FALLOC_FL_KEEP_SIZE; struct nvme_dsm_range range; loff_t offset, len; + bool associated; u16 status = 0; int ret; int i; + associated = nvmet_blkcg_begin(req); for (i = 0; i <= le32_to_cpu(req->cmd->dsm.nr); i++) { status = nvmet_copy_from_sgl(req, i sizeof(range), &range, sizeof(range)); @@ -300,6 +307,7 @@ static void nvmet_file_execute_discard(struct nvmet_req req) break; } } + nvmet_blkcg_end(associated); nvmet_req_complete(req, status); } @@ -326,7 +334,7 @@ static void nvmet_file_execute_dsm(struct nvmet_req req) if (!nvmet_check_data_len_lte(req, nvmet_dsm_len(req))) return; INIT_WORK(&req->f.work, nvmet_file_dsm_work); - queue_work(nvmet_wq, &req->f.work); + nvmet_req_queue_work(req, nvmet_wq, &req->f.work); } static void nvmet_file_write_zeroes_work(struct work_struct w) @@ -336,6 +344,7 @@ static void nvmet_file_write_zeroes_work(struct work_struct w) int mode = FALLOC_FL_ZERO_RANGE \| FALLOC_FL_KEEP_SIZE; loff_t offset; loff_t len; + bool associated; int ret; offset = le64_to_cpu(write_zeroes->slba) << req->ns->blksize_shift; @@ -347,7 +356,9 @@ static void nvmet_file_write_zeroes_work(struct work_struct w) return; } + associated = nvmet_blkcg_begin(req); ret = vfs_fallocate(req->ns->file, mode, offset, len); + nvmet_blkcg_end(associated); nvmet_req_complete(req, ret < 0 ? errno_to_nvme_status(req, ret) : 0); } @@ -356,7 +367,7 @@ static void nvmet_file_execute_write_zeroes(struct nvmet_req req) if (!nvmet_check_transfer_len(req, 0)) return; INIT_WORK(&req->f.work, nvmet_file_write_zeroes_work); - queue_work(nvmet_wq, &req->f.work); + nvmet_req_queue_work(req, nvmet_wq, &req->f.work); } u16 nvmet_file_parse_io_cmd(struct nvmet_req req) diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h index 9cec19e6f4857e..4eac1b5195a855 100644 --- a/drivers/nvme/target/nvmet.h +++ b/drivers/nvme/target/nvmet.h @@ -117,6 +117,22 @@ struct nvmet_ns { struct nvmet_subsys subsys; const char device_path; +#ifdef CONFIG_BLK_CGROUP + u64 cgroup_id; + / + * Resolved from ->cgroup_id when the namespace is enabled and + * released when it is disabled, so it has the same lifetime and + * visibility rules as ->bdev and ->file. + / + struct cgroup cgrp; + /* + * The I/O commands of a namespace with a cgroup, except Reservation + * commands, are executed from their own work items on ->blkcg_wq, so + * the cgroup's throttling doesn't put a transport context to sleep. + / + struct workqueue_struct blkcg_wq; +#endif + struct config_group device_group; struct config_group group; @@ -509,6 +525,11 @@ struct nvmet_req { void (execute)(struct nvmet_req req); const struct nvmet_fabrics_ops ops; +#ifdef CONFIG_BLK_CGROUP + / the backend's ->execute, called from ->blkcg_work / + void (blkcg_execute)(struct nvmet_req req); + struct work_struct blkcg_work; +#endif struct pci_dev p2p_dev; struct device p2p_client; @@ -748,6 +769,36 @@ void nvmet_bdev_execute_zone_mgmt_recv(struct nvmet_req req); void nvmet_bdev_execute_zone_mgmt_send(struct nvmet_req req); void nvmet_bdev_execute_zone_append(struct nvmet_req req); +#ifdef CONFIG_BLK_CGROUP +bool nvmet_blkcg_begin(struct nvmet_req req); +void nvmet_blkcg_end(bool associated); +#else +static inline bool nvmet_blkcg_begin(struct nvmet_req req) +{ + return false; +} + +static inline void nvmet_blkcg_end(bool associated) +{ +} +#endif /* CONFIG_BLK_CGROUP / + +/ + * The backends' work items of a namespace with a cgroup may sleep in the + * cgroup's throttling, so queue them on the namespace's own workqueue, + * where they can't use up the max_active or the rescuer of a workqueue + * that other namespaces share. + / +static inline void nvmet_req_queue_work(struct nvmet_req req, + struct workqueue_struct wq, struct work_struct work) +{ +#ifdef CONFIG_BLK_CGROUP + if (req->ns->blkcg_wq) + wq = req->ns->blkcg_wq; +#endif + queue_work(wq, work); +} + static inline u32 nvmet_rw_data_len(struct nvmet_req req) { return ((u32)le16_to_cpu(req->cmd->rw.length) + 1) << diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c index 78d82b6ff1214e..33faf32a1a3bfd 100644 --- a/drivers/nvme/target/zns.c +++ b/drivers/nvme/target/zns.c @@ -490,8 +490,11 @@ static void nvmet_bdev_zmgmt_send_work(struct work_struct w) struct block_device bdev = req->ns->bdev; sector_t zone_sectors = bdev_zone_sectors(bdev); u16 status = NVME_SC_SUCCESS; + bool associated; int ret; + associated = nvmet_blkcg_begin(req); + if (op == REQ_OP_LAST) { req->error_loc = offsetof(struct nvme_zone_mgmt_send_cmd, zsa); status = NVME_SC_ZONE_INVALID_TRANSITION \| NVME_STATUS_DNR; @@ -521,13 +524,14 @@ static void nvmet_bdev_zmgmt_send_work(struct work_struct w) status = blkdev_zone_mgmt_errno_to_nvme_status(ret); out: + nvmet_blkcg_end(associated); nvmet_req_complete(req, status); } void nvmet_bdev_execute_zone_mgmt_send(struct nvmet_req req) { INIT_WORK(&req->z.zmgmt_work, nvmet_bdev_zmgmt_send_work); - queue_work(zbd_wq, &req->z.zmgmt_work); + nvmet_req_queue_work(req, zbd_wq, &req->z.zmgmt_work); } static void nvmet_bdev_zone_append_bio_done(struct bio bio)
25/3	2026/10/26 20:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 7931 output: 39 thoughts: 1463 Thoughts: KMSAN Evaluation: NVMe ConfigFS cgroup_id Support Okay, let's break this down. My goal here is to determine if this patch warrants a dedicated KMSAN fuzzing session. I need to be precise, as these sessions are resource-intensive. The guidelines are clear: KMSAN is for detecting uninitialized memory reads or information leaks that aren't caught by KASAN, LockDep, or other standard detectors. Looking at the patch, it seems to add cgroup integration for NVMe namespaces, specifically around block I/O controller integration. The changes primarily focus on allowing userspace configuration of a `cgroup_id` for NVMe namespaces via configfs, and then using this `cgroup_id` for block I/O controller (blkcg) association. The key areas I'm concerned with are: 1. Data structures exposed to userspace: The patch introduces `cgroup_id` which is a `u64` that's written to user space in `nvmet_ns_cgroup_id_show`. The `snprintf` looks safe, but I need to make sure the value is initialized. 2. Conditional logic and uninitialized variables: The code conditionally includes the block I/O controller integration based on `CONFIG_BLK_CGROUP`. The critical part, here, is that the `cgroup_id` is only used if block I/O controller integration is enabled, so I will have to ensure that this variable is properly initialized. I need to track where `ns->cgroup_id` is allocated and initialized in `struct nvmet_ns`. 3. Complex data structure initialization: The patch adds fields to `struct nvmet_ns` and `struct nvmet_req`. These are: `u64 cgroup_id; struct cgroup cgrp; struct workqueue_struct blkcg_wq; void (blkcg_execute)(struct nvmet_req req); struct work_struct blkcg_work;`. I need to track when these structs are allocated, initialized, and freed. Are the added fields initialized before being used, and what are the default values? It's essential to check if these new fields could lead to uninitialized memory being read. The code itself reads the `cgroup_id` using `kstrtou64`, so the assumption is that the value is provided by the user and therefore initialized. My concern would be if there are any default values, or if we read the value before being written to. Therefore, my immediate plan is to use `grepper` (or similar) to meticulously trace the allocation and initialization of `struct nvmet_ns` and `struct nvmet_req`. I need to ensure that the newly added fields, especially `cgroup_id`, `cgrp`, `blkcg_wq`, `blkcg_execute`, and `blkcg_work`, are always initialized before use. The primary risk here appears to be uninitialized reads of these fields, and potential information leaks through `configfs`. It is paramount to check if all the code paths ensure the proper initialization of the added fields to these structs. Depending on the results of the `grepper` search, I can determine whether KMSAN fuzzing is warranted or if standard bug detectors will be sufficient.
26/3	2026/10/26 20:26	tool	grepper	0m Error: no matches Args: { "Expression": "kzalloc\\(.sizeof\\(struct nvmet_ns", "PathPrefixes": [ "drivers/nvme/target/" ] } Results:* { "error": "no matches" }
27/3	2026/10/26 20:26	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10159 output: 34 thoughts: 11 Thoughts: Okay, here's my attempt at summarizing that thought process, tailored for an expert audience: Investigating nvmet_ns Allocations Alright, let's dive in. I need to get a handle on the `nvmet_ns` allocations. Specifically, I'm thinking about the low-level memory management and how namespaces are being handled within the NVMe over Fabrics context. My goal is to understand how these namespaces are being created, tracked, and potentially, where performance bottlenecks or resource contention might be occurring. I'm imagining digging into kernel structures, perhaps tracing allocation calls with `kmalloc`/`kmem_cache_alloc` or similar, looking for any unusual patterns or unexpected behavior. I'm anticipating possibly needing to correlate these allocations with specific fabric connections, identify potentially fragmented or inefficient allocation strategies, or investigate if any resource leaks are occurring, leading to memory exhaustion over time. The allocation strategy of `nvmet_ns` is a key component to understanding how the storage system performs and potential points of failure or performance bottlenecks.
28/3	2026/10/26 20:26	tool	grepper	0m Args: { "Expression": "nvmet_ns_alloc", "PathPrefixes": [ "drivers/nvme/target/" ] } Results: { "Output": "drivers/nvme/target/configfs.c=909=static struct config_group nvmet_ns_make(struct config_group group,\n--\ndrivers/nvme/target/configfs.c-927-\tret = -ENOMEM;\ndrivers/nvme/target/configfs.c:928:\tns = nvmet_ns_alloc(subsys, nsid);\ndrivers/nvme/target/configfs.c-929-\tif (!ns)\n--\ndrivers/nvme/target/core.c=833=void nvmet_ns_free(struct nvmet_ns ns)\n--\ndrivers/nvme/target/core.c-855-\ndrivers/nvme/target/core.c:856:struct nvmet_ns nvmet_ns_alloc(struct nvmet_subsys subsys, u32 nsid)\ndrivers/nvme/target/core.c-857-{\n--\ndrivers/nvme/target/nvmet.h=677=void nvmet_ns_disable(struct nvmet_ns ns);\ndrivers/nvme/target/nvmet.h:678:struct nvmet_ns nvmet_ns_alloc(struct nvmet_subsys subsys, u32 nsid);\ndrivers/nvme/target/nvmet.h-679-void nvmet_ns_free(struct nvmet_ns *ns);\n" }
29/3	2026/10/26 20:26	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10779 output: 38 thoughts: 25 Thoughts: Okay, let's dive into this. Here's my take on understanding this code: Analyzing `nvmet_ns_alloc` Right, time to dig into `nvmet_ns_alloc`. I know it's in `drivers/nvme/target/core.c`, so that's where I'll start. Given my expertise, I'm expecting this function to handle the allocation of a namespace within the NVMe target context. I'll be looking for how it interacts with the underlying data structures for namespaces, how it handles potential errors (like resource exhaustion or configuration issues), and what its overall role is in the lifecycle of a namespace within the NVMe target. I need to understand how the allocation is tied to the overall architecture, specifically how the namespace is integrated with the host and data transfer.
30/3	2026/10/26 20:26	tool	read-file	0m Args: { "File": "drivers/nvme/target/core.c", "FirstLine": 856, "LineCount": 40 } Results: { "Contents": " 856:\tstruct nvmet_ns nvmet_ns_alloc(struct nvmet_subsys subsys, u32 nsid)\n 857:\t{\n 858:\t\tstruct nvmet_ns ns;\n 859:\t\n 860:\t\tmutex_lock(\u0026subsys-\u003elock);\n 861:\t\n 862:\t\tif (subsys-\u003enr_namespaces == NVMET_MAX_NAMESPACES)\n 863:\t\t\tgoto out_unlock;\n 864:\t\n 865:\t\tns = kzalloc_obj(ns);\n 866:\t\tif (!ns)\n 867:\t\t\tgoto out_unlock;\n 868:\t\n 869:\t\tinit_completion(\u0026ns-\u003edisable_done);\n 870:\t\n 871:\t\tns-\u003ensid = nsid;\n 872:\t\tns-\u003esubsys = subsys;\n 873:\t\n 874:\t\tif (ns-\u003ensid \u003e subsys-\u003emax_nsid)\n 875:\t\t\tsubsys-\u003emax_nsid = nsid;\n 876:\t\n 877:\t\tif (xa_insert(\u0026subsys-\u003enamespaces, ns-\u003ensid, ns, GFP_KERNEL))\n 878:\t\t\tgoto out_exit;\n 879:\t\n 880:\t\tsubsys-\u003enr_namespaces++;\n 881:\t\n 882:\t\tmutex_unlock(\u0026subsys-\u003elock);\n 883:\t\n 884:\t\tdown_write(\u0026nvmet_ana_sem);\n 885:\t\tns-\u003eanagrpid = NVMET_DEFAULT_ANA_GRPID;\n 886:\t\tnvmet_ana_group_enabled[ns-\u003eanagrpid]++;\n 887:\t\tup_write(\u0026nvmet_ana_sem);\n 888:\t\n 889:\t\tuuid_gen(\u0026ns-\u003euuid);\n 890:\t\tns-\u003ebuffered_io = false;\n 891:\t\tns-\u003ecsi = NVME_CSI_NVM;\n 892:\t\n 893:\t\treturn ns;\n 894:\tout_exit:\n 895:\t\tsubsys-\u003emax_nsid = nvmet_max_nsid(subsys);\n" }
31/3	2026/10/26 20:26	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 11603 output: 33 thoughts: 49 Thoughts: Okay, here's my take on those thoughts, framed as my own mental process, given my expertise: Checking Allocation and Initialization Alright, so `kzalloc_obj(*ns)` zeroes out my `struct nvmet_ns`. That's standard practice, ensuring a clean slate before I start populating it with namespace information. But now my focus shifts to the request handling. I need to understand the allocation and initialization of the `struct nvmet_req`. That's the core of how I'm going to process I/O. I need to see how the driver is handling the incoming requests. Understanding this will be critical to performance tuning and debugging down the line. Let's see how `struct nvmet_req` is created and configured. I need to make sure I'm not overlooking any potential issues with memory allocation or initialization.
32/3	2026/10/26 20:26	tool	grepper	0m Args: { "Expression": "struct nvmet_req", "PathPrefixes": [ "drivers/nvme/target/" ] } Results: { "Output": "\nFull output is too long, showing 200 out of 1258 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (18 files in total):\ndrivers/nvme/target/admin-cmd.c:50\ndrivers/nvme/target/auth.c:5\ndrivers/nvme/target/core.c:33\ndrivers/nvme/target/discovery.c:8\ndrivers/nvme/target/fabrics-cmd-auth.c:9\ndrivers/nvme/target/fabrics-cmd.c:11\ndrivers/nvme/target/fc.c:4\ndrivers/nvme/target/io-cmd-bdev.c:11\ndrivers/nvme/target/io-cmd-file.c:15\ndrivers/nvme/target/loop.c:3\ndrivers/nvme/target/nvmet.h:91\ndrivers/nvme/target/passthru.c:12\ndrivers/nvme/target/pci-epf.c:4\ndrivers/nvme/target/pr.c:26\ndrivers/nvme/target/rdma.c:6\ndrivers/nvme/target/tcp.c:5\ndrivers/nvme/target/trace.h:4\ndrivers/nvme/target/zns.c:16\n\ndrivers/nvme/target/admin-cmd.c-14-\ndrivers/nvme/target/admin-cmd.c:15:static void nvmet_execute_delete_sq(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-16-{\n--\ndrivers/nvme/target/admin-cmd.c-40-\ndrivers/nvme/target/admin-cmd.c:41:static void nvmet_execute_create_sq(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-42-{\n--\ndrivers/nvme/target/admin-cmd.c-82-\ndrivers/nvme/target/admin-cmd.c:83:static void nvmet_execute_delete_cq(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-84-{\n--\ndrivers/nvme/target/admin-cmd.c-109-\ndrivers/nvme/target/admin-cmd.c:110:static void nvmet_execute_create_cq(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-111-{\n--\ndrivers/nvme/target/admin-cmd.c=142=u32 nvmet_get_log_page_len(struct nvme_command cmd)\n--\ndrivers/nvme/target/admin-cmd.c-154-\ndrivers/nvme/target/admin-cmd.c:155:static u32 nvmet_feat_data_len(struct nvmet_req req, u32 cdw10)\ndrivers/nvme/target/admin-cmd.c-156-{\n--\ndrivers/nvme/target/admin-cmd.c=165=u64 nvmet_get_log_page_offset(struct nvme_command cmd)\n--\ndrivers/nvme/target/admin-cmd.c-169-\ndrivers/nvme/target/admin-cmd.c:170:static void nvmet_execute_get_log_page_noop(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-171-{\n--\ndrivers/nvme/target/admin-cmd.c-174-\ndrivers/nvme/target/admin-cmd.c:175:static void nvmet_execute_get_log_page_error(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-176-{\n--\ndrivers/nvme/target/admin-cmd.c-200-\ndrivers/nvme/target/admin-cmd.c:201:static void nvmet_execute_get_supported_log_pages(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-202-{\n--\ndrivers/nvme/target/admin-cmd.c-229-\ndrivers/nvme/target/admin-cmd.c:230:static u16 nvmet_get_smart_log_nsid(struct nvmet_req req,\ndrivers/nvme/target/admin-cmd.c-231-\t\tstruct nvme_smart_log slog)\n--\ndrivers/nvme/target/admin-cmd.c-258-\ndrivers/nvme/target/admin-cmd.c:259:static u16 nvmet_get_smart_log_all(struct nvmet_req req,\ndrivers/nvme/target/admin-cmd.c-260-\t\tstruct nvme_smart_log slog)\n--\ndrivers/nvme/target/admin-cmd.c-288-\ndrivers/nvme/target/admin-cmd.c:289:static void nvmet_execute_get_log_page_rmi(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-290-{\n--\ndrivers/nvme/target/admin-cmd.c-329-\ndrivers/nvme/target/admin-cmd.c:330:static void nvmet_execute_get_log_page_smart(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-331-{\n--\ndrivers/nvme/target/admin-cmd.c=399=static void nvmet_get_cmd_effects_zns(struct nvme_effects_log log)\n--\ndrivers/nvme/target/admin-cmd.c-407-\ndrivers/nvme/target/admin-cmd.c:408:static void nvmet_execute_get_log_cmd_effects_ns(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-409-{\n--\ndrivers/nvme/target/admin-cmd.c-445-\ndrivers/nvme/target/admin-cmd.c:446:static void nvmet_execute_get_log_changed_ns(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-447-{\n--\ndrivers/nvme/target/admin-cmd.c-469-\ndrivers/nvme/target/admin-cmd.c:470:static u32 nvmet_format_ana_group(struct nvmet_req req, u32 grpid,\ndrivers/nvme/target/admin-cmd.c-471-\t\tstruct nvme_ana_group_desc desc)\n--\ndrivers/nvme/target/admin-cmd.c-492-\ndrivers/nvme/target/admin-cmd.c:493:static void nvmet_execute_get_log_page_endgrp(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-494-{\n--\ndrivers/nvme/target/admin-cmd.c-535-\ndrivers/nvme/target/admin-cmd.c:536:static void nvmet_execute_get_log_page_ana(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-537-{\n--\ndrivers/nvme/target/admin-cmd.c-579-\ndrivers/nvme/target/admin-cmd.c:580:static void nvmet_execute_get_log_page_features(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-581-{\n--\ndrivers/nvme/target/admin-cmd.c-609-\ndrivers/nvme/target/admin-cmd.c:610:static void nvmet_execute_get_log_page(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-611-{\n--\ndrivers/nvme/target/admin-cmd.c-649-\ndrivers/nvme/target/admin-cmd.c:650:static void nvmet_execute_identify_ctrl(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-651-{\n--\ndrivers/nvme/target/admin-cmd.c-799-\ndrivers/nvme/target/admin-cmd.c:800:static void nvmet_execute_identify_ns(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-801-{\n--\ndrivers/nvme/target/admin-cmd.c-901-\ndrivers/nvme/target/admin-cmd.c:902:static void nvmet_execute_identify_endgrp_list(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-903-{\n--\ndrivers/nvme/target/admin-cmd.c-934-\ndrivers/nvme/target/admin-cmd.c:935:static void nvmet_execute_identify_nslist(struct nvmet_req req, bool match_css)\ndrivers/nvme/target/admin-cmd.c-936-{\n--\ndrivers/nvme/target/admin-cmd.c-978-\ndrivers/nvme/target/admin-cmd.c:979:static u16 nvmet_copy_ns_identifier(struct nvmet_req req, u8 type, u8 len,\ndrivers/nvme/target/admin-cmd.c-980-\t\t\t\t void id, off_t off)\n--\ndrivers/nvme/target/admin-cmd.c-1000-\ndrivers/nvme/target/admin-cmd.c:1001:static void nvmet_execute_identify_desclist(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1002-{\n--\ndrivers/nvme/target/admin-cmd.c-1038-\ndrivers/nvme/target/admin-cmd.c:1039:static void nvmet_execute_identify_ctrl_nvm(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1040-{\n--\ndrivers/nvme/target/admin-cmd.c-1045-\ndrivers/nvme/target/admin-cmd.c:1046:static void nvme_execute_identify_ns_nvm(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1047-{\n--\ndrivers/nvme/target/admin-cmd.c-1067-\ndrivers/nvme/target/admin-cmd.c:1068:static void nvmet_execute_id_cs_indep(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1069-{\n--\ndrivers/nvme/target/admin-cmd.c-1103-\ndrivers/nvme/target/admin-cmd.c:1104:static void nvmet_execute_identify(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1105-{\n--\ndrivers/nvme/target/admin-cmd.c-1171- /\ndrivers/nvme/target/admin-cmd.c:1172:static void nvmet_execute_abort(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1173-{\n--\ndrivers/nvme/target/admin-cmd.c-1179-\ndrivers/nvme/target/admin-cmd.c:1180:static u16 nvmet_write_protect_flush_sync(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1181-{\n--\ndrivers/nvme/target/admin-cmd.c-1193-\ndrivers/nvme/target/admin-cmd.c:1194:static u16 nvmet_set_feat_write_protect(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1195-{\n--\ndrivers/nvme/target/admin-cmd.c-1225-\ndrivers/nvme/target/admin-cmd.c:1226:u16 nvmet_set_feat_kato(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1227-{\n--\ndrivers/nvme/target/admin-cmd.c-1238-\ndrivers/nvme/target/admin-cmd.c:1239:u16 nvmet_set_feat_async_event(struct nvmet_req req, u32 mask)\ndrivers/nvme/target/admin-cmd.c-1240-{\n--\ndrivers/nvme/target/admin-cmd.c-1253-\ndrivers/nvme/target/admin-cmd.c:1254:static u16 nvmet_set_feat_host_id(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1255-{\n--\ndrivers/nvme/target/admin-cmd.c-1278-\ndrivers/nvme/target/admin-cmd.c:1279:static u16 nvmet_set_feat_irq_coalesce(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1280-{\n--\ndrivers/nvme/target/admin-cmd.c-1299-\ndrivers/nvme/target/admin-cmd.c:1300:static u16 nvmet_set_feat_irq_config(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1301-{\n--\ndrivers/nvme/target/admin-cmd.c-1320-\ndrivers/nvme/target/admin-cmd.c:1321:static u16 nvmet_set_feat_arbitration(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1322-{\n--\ndrivers/nvme/target/admin-cmd.c-1339-\ndrivers/nvme/target/admin-cmd.c:1340:void nvmet_execute_set_features(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1341-{\n--\ndrivers/nvme/target/admin-cmd.c-1395-\ndrivers/nvme/target/admin-cmd.c:1396:static u16 nvmet_get_feat_write_protect(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1397-{\n--\ndrivers/nvme/target/admin-cmd.c-1415-\ndrivers/nvme/target/admin-cmd.c:1416:static u16 nvmet_get_feat_irq_coalesce(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1417-{\n--\ndrivers/nvme/target/admin-cmd.c-1439-\ndrivers/nvme/target/admin-cmd.c:1440:static u16 nvmet_get_feat_irq_config(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1441-{\n--\ndrivers/nvme/target/admin-cmd.c-1464-\ndrivers/nvme/target/admin-cmd.c:1465:static u16 nvmet_get_feat_arbitration(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1466-{\n--\ndrivers/nvme/target/admin-cmd.c-1488-\ndrivers/nvme/target/admin-cmd.c:1489:void nvmet_get_feat_kato(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1490-{\n--\ndrivers/nvme/target/admin-cmd.c-1493-\ndrivers/nvme/target/admin-cmd.c:1494:void nvmet_get_feat_async_event(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1495-{\n--\ndrivers/nvme/target/admin-cmd.c-1498-\ndrivers/nvme/target/admin-cmd.c:1499:void nvmet_execute_get_features(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1500-{\n--\ndrivers/nvme/target/admin-cmd.c-1573-\ndrivers/nvme/target/admin-cmd.c:1574:void nvmet_execute_async_event(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1575-{\n--\ndrivers/nvme/target/admin-cmd.c-1592-\ndrivers/nvme/target/admin-cmd.c:1593:void nvmet_execute_keep_alive(struct nvmet_req req)\ndrivers/nvme/target/admin-cmd.c-1594-{\n--\ndrivers/nvme/target/admin-cmd.c-1612-\ndrivers/nvme/target/admin-cmd.c:1613:u32 nvmet_admin_cmd_data_len(struct nvmet_req req)\n\n" }
33/3	2026/10/26 20:26	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16247 output: 34 thoughts: 20 Thoughts: Here's my take on those thoughts: Tracing the Origins of the NVMe Request Structure Alright, let's get down to brass tacks. I need to understand the lifecycle of the NVMe request structure. My immediate thought is to pinpoint its initialization. So, the first step is to trace where `nvmet_req` is initially set up. I'll start with the function `nvmet_req_init`. That's where I expect to find the genesis of this crucial data structure. From there, I can begin my investigation.
34/3	2026/10/26 20:26	tool	grepper	0m Args: { "Expression": "nvmet_req_init", "PathPrefixes": [ "drivers/nvme/target/" ] } Results: { "Output": "drivers/nvme/target/core.c=1253=static u16 nvmet_parse_io_cmd(struct nvmet_req req)\n--\ndrivers/nvme/target/core.c-1322-\ndrivers/nvme/target/core.c:1323:bool nvmet_req_init(struct nvmet_req req, struct nvmet_sq sq,\ndrivers/nvme/target/core.c-1324-\t\tconst struct nvmet_fabrics_ops ops)\n--\ndrivers/nvme/target/core.c-1378-\ndrivers/nvme/target/core.c:1379:\ttrace_nvmet_req_init(req, req-\u003ecmd);\ndrivers/nvme/target/core.c-1380-\n--\ndrivers/nvme/target/core.c-1394-}\ndrivers/nvme/target/core.c:1395:EXPORT_SYMBOL_GPL(nvmet_req_init);\ndrivers/nvme/target/core.c-1396-\n--\ndrivers/nvme/target/fc.c=2525=nvmet_fc_handle_fcp_rqst(struct nvmet_fc_tgtport tgtport,\n--\ndrivers/nvme/target/fc.c-2568-\ndrivers/nvme/target/fc.c:2569:\tret = nvmet_req_init(\u0026fod-\u003ereq, \u0026fod-\u003equeue-\u003envme_sq,\ndrivers/nvme/target/fc.c-2570-\t\t\t\u0026nvmet_fc_tgt_fcp_ops);\n--\ndrivers/nvme/target/loop.c=133=static blk_status_t nvme_loop_queue_rq(struct blk_mq_hw_ctx hctx,\n--\ndrivers/nvme/target/loop.c-152-\tiod-\u003ereq.port = queue-\u003ectrl-\u003eport;\ndrivers/nvme/target/loop.c:153:\tif (!nvmet_req_init(\u0026iod-\u003ereq, \u0026queue-\u003envme_sq, \u0026nvme_loop_ops))\ndrivers/nvme/target/loop.c-154-\t\treturn BLK_STS_OK;\n--\ndrivers/nvme/target/loop.c=174=static void nvme_loop_submit_async_event(struct nvme_ctrl arg)\n--\ndrivers/nvme/target/loop.c-184-\ndrivers/nvme/target/loop.c:185:\tif (!nvmet_req_init(\u0026iod-\u003ereq, \u0026queue-\u003envme_sq, \u0026nvme_loop_ops)) {\ndrivers/nvme/target/loop.c-186-\t\tdev_err(ctrl-\u003ectrl.device, \"failed async event work\\n\");\n--\ndrivers/nvme/target/nvmet.h=607=u32 nvmet_fabrics_io_cmd_data_len(struct nvmet_req req);\ndrivers/nvme/target/nvmet.h-608-\ndrivers/nvme/target/nvmet.h:609:bool nvmet_req_init(struct nvmet_req req, struct nvmet_sq sq,\ndrivers/nvme/target/nvmet.h-610-\t\tconst struct nvmet_fabrics_ops ops);\n--\ndrivers/nvme/target/pci-epf.c=1573=static void nvmet_pci_epf_exec_iod_work(struct work_struct work)\n--\ndrivers/nvme/target/pci-epf.c-1591-\t/\ndrivers/nvme/target/pci-epf.c:1592:\t If nvmet_req_init() fails (e.g., unsupported opcode) it will call\ndrivers/nvme/target/pci-epf.c-1593-\t * __nvmet_req_complete() internally which will call\n--\ndrivers/nvme/target/pci-epf.c-1595-\t /\ndrivers/nvme/target/pci-epf.c:1596:\tif (!nvmet_req_init(req, \u0026iod-\u003esq-\u003envme_sq, \u0026nvmet_pci_epf_fabrics_ops))\ndrivers/nvme/target/pci-epf.c-1597-\t\treturn;\n--\ndrivers/nvme/target/rdma.c=976=static void nvmet_rdma_handle_command(struct nvmet_rdma_queue queue,\n--\ndrivers/nvme/target/rdma.c-987-\ndrivers/nvme/target/rdma.c:988:\tif (!nvmet_req_init(\u0026cmd-\u003ereq, \u0026queue-\u003envme_sq, \u0026nvmet_rdma_ops))\ndrivers/nvme/target/rdma.c-989-\t\treturn;\n--\ndrivers/nvme/target/tcp.c=603=static void nvmet_tcp_queue_response(struct nvmet_req req)\n--\ndrivers/nvme/target/tcp.c-623-\t\t Avoid using helpers, this might happen before\ndrivers/nvme/target/tcp.c:624:\t\t * nvmet_req_init is completed.\ndrivers/nvme/target/tcp.c-625-\t\t /\n--\ndrivers/nvme/target/tcp.c=1066=static int nvmet_tcp_done_recv_pdu(struct nvmet_tcp_queue queue)\n--\ndrivers/nvme/target/tcp.c-1106-\ndrivers/nvme/target/tcp.c:1107:\tif (unlikely(!nvmet_req_init(req, \u0026queue-\u003envme_sq, \u0026nvmet_tcp_ops))) {\ndrivers/nvme/target/tcp.c-1108-\t\tpr_err(\"failed cmd %p id %d opcode %d, data_len: %d, status: %04x\\n\",\n--\ndrivers/nvme/target/trace.h=55=static inline void __assign_req_name(char name, struct nvmet_req req)\n--\ndrivers/nvme/target/trace.h-65-\ndrivers/nvme/target/trace.h:66:TRACE_EVENT(nvmet_req_init,\ndrivers/nvme/target/trace.h-67-\tTP_PROTO(struct nvmet_req req, struct nvme_command cmd),\n" }
35/3	2026/10/26 20:26	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18023 output: 39 thoughts: 25 Thoughts: Okay, let's dive into this. Here's my summary, taking on the persona you requested: Deconstructing `nvmet_req_init` Alright, time to get to it. I need to take a close look at the `nvmet_req_init` function. The first step is to locate it – no problem, it's right where I'd expect it, tucked away in `drivers/nvme/target/core.c`. This is the core NVMe target code, so `nvmet_req_init` must be a fundamental building block. It's likely responsible for initializing the request structure that sits at the heart of all NVMe I/O operations. I need to figure out exactly how the request object is brought into existence, and how it is linked to the relevant transport, queue, and device context. I'll need to understand what parameters are initialized, what data structures it touches, and how this relates to the overall I/O flow. Any flags, counters, or pointers within the initialized structure warrant a closer look. I'm expecting this function to be critical in setting the stage for handling incoming commands and ultimately getting the data written or read from the target device. Let's see how they do it.
36/3	2026/10/26 20:26	tool	read-file	0m Args: { "File": "drivers/nvme/target/core.c", "FirstLine": 1320, "LineCount": 70 } Results: { "Contents": "1320:\t\treturn ret;\n1321:\t}\n1322:\t\n1323:\tbool nvmet_req_init(struct nvmet_req req, struct nvmet_sq sq,\n1324:\t\t\tconst struct nvmet_fabrics_ops ops)\n1325:\t{\n1326:\t\tu8 flags = req-\u003ecmd-\u003ecommon.flags;\n1327:\t\tu16 status;\n1328:\t\n1329:\t\treq-\u003ecq = sq-\u003ecq;\n1330:\t\treq-\u003esq = sq;\n1331:\t\treq-\u003eops = ops;\n1332:\t\treq-\u003esg = NULL;\n1333:\t\treq-\u003emetadata_sg = NULL;\n1334:\t\treq-\u003esg_cnt = 0;\n1335:\t\treq-\u003emetadata_sg_cnt = 0;\n1336:\t\treq-\u003etransfer_len = 0;\n1337:\t\treq-\u003emetadata_len = 0;\n1338:\t\treq-\u003ecqe-\u003eresult.u64 = 0;\n1339:\t\treq-\u003ecqe-\u003estatus = 0;\n1340:\t\treq-\u003ecqe-\u003esq_head = 0;\n1341:\t\treq-\u003ens = NULL;\n1342:\t\treq-\u003eerror_loc = NVMET_NO_ERROR_LOC;\n1343:\t\treq-\u003eerror_slba = 0;\n1344:\t\treq-\u003epc_ref = NULL;\n1345:\t\treq-\u003ep.ref_held = false;\n1346:\t\n1347:\t\t/ no support for fused commands yet /\n1348:\t\tif (unlikely(flags \u0026 (NVME_CMD_FUSE_FIRST \| NVME_CMD_FUSE_SECOND))) {\n1349:\t\t\treq-\u003eerror_loc = offsetof(struct nvme_common_command, flags);\n1350:\t\t\tstatus = NVME_SC_INVALID_FIELD \| NVME_STATUS_DNR;\n1351:\t\t\tgoto fail;\n1352:\t\t}\n1353:\t\n1354:\t\t/\n1355:\t\t * For fabrics, PSDT field shall describe metadata pointer (MPTR) that\n1356:\t\t * contains an address of a single contiguous physical buffer that is\n1357:\t\t * byte aligned. For PCI controllers, this is optional so not enforced.\n1358:\t\t /\n1359:\t\tif (unlikely((flags \u0026 NVME_CMD_SGL_ALL) != NVME_CMD_SGL_METABUF)) {\n1360:\t\t\tif (!req-\u003esq-\u003ectrl \|\| !nvmet_is_pci_ctrl(req-\u003esq-\u003ectrl)) {\n1361:\t\t\t\treq-\u003eerror_loc =\n1362:\t\t\t\t\toffsetof(struct nvme_common_command, flags);\n1363:\t\t\t\tstatus = NVME_SC_INVALID_FIELD \| NVME_STATUS_DNR;\n1364:\t\t\t\tgoto fail;\n1365:\t\t\t}\n1366:\t\t}\n1367:\t\n1368:\t\tif (unlikely(!req-\u003esq-\u003ectrl))\n1369:\t\t\t/ will return an error for any non-connect command: */\n1370:\t\t\tstatus = nvmet_parse_connect_cmd(req);\n1371:\t\telse if (likely(req-\u003esq-\u003eqid != 0))\n1372:\t\t\tstatus = nvmet_parse_io_cmd(req);\n1373:\t\telse\n1374:\t\t\tstatus = nvmet_parse_admin_cmd(req);\n1375:\t\n1376:\t\tif (status)\n1377:\t\t\tgoto fail;\n1378:\t\n1379:\t\ttrace_nvmet_req_init(req, req-\u003ecmd);\n1380:\t\n1381:\t\tif (unlikely(!percpu_ref_tryget_live(\u0026sq-\u003eref))) {\n1382:\t\t\tstatus = NVME_SC_INVALID_FIELD \| NVME_STATUS_DNR;\n1383:\t\t\tgoto fail;\n1384:\t\t}\n1385:\t\n1386:\t\tif (sq-\u003ectrl \u0026\u0026 sq-\u003ectrl-\u003etbkas)\n1387:\t\t\tsq-\u003ectrl-\u003ereset_tbkas = true;\n1388:\t\n1389:\t\treturn true;\n" }
37/3	2026/10/26 20:26	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 19464 output: 342 thoughts: 2236 Thoughts: KMSAN Applicability Analysis for NVMe-oF Cgroup Integration Alright, let's break down this patch and assess the KMSAN implications, keeping in mind my experience and knowledge of the kernel's memory safety mechanisms. The primary focus here is integrating block I/O cgroups into the NVMe-oF target code, specifically regarding request execution and resource management. Initially, I'm tracing the execution flow of `blkcg_execute` and `blkcg_work`. I see how `nvmet_blkcg_init_req` conditionally sets up the `blkcg_execute` and `blkcg_work` for a request based on whether a cgroup is associated with the namespace (`req->ns->cgrp`). If a cgroup is active, `nvmet_blkcg_queue_req` queues a work item to `req->ns->blkcg_wq`, otherwise the original `req->execute` is preserved, as expected. I'm noting the clear separation between the "normal" I/O path and the cgroup-aware I/O path. I'm then checking the `nvmet_ns_cgroup_id_show` function, confirming that the cgroup ID is retrieved and formatted for user space. The `u64 ns->cgroup_id` is zero-initialized during allocation with `kzalloc_obj`, and `snprintf` is used. This is crucial for preventing any accidental information leaks via uninitialized memory. I'm also confirming that other functions, such as `nvmet_ns_cgroup_id_store`, are setting `cgroup_id` to a value. Next, I'm meticulously looking for any potential reads of uninitialized memory, paying attention to what's being copied to user space, or where new variables have been introduced. I'm reviewing the changes in functions like `nvmet_file_execute_discard`, `nvmet_file_flush_work`, and `nvmet_bdev_zmgmt_send_work`. I'm focusing specifically on added variables like `associated` and `status`, confirming that all introduced variables are properly initialized before use. The `nvmet_blkcg_begin` and `nvmet_blkcg_end` are also inspected, which encapsulate the cgroup context management. The core of my analysis hinges on the state of variables before their use, specifically checking that variables such as `associated` and `noio_flag` are assigned to a definite value by the calls to `nvmet_blkcg_begin` or `memalloc_noio_save()`. `status` is assigned the return value from `nvmet_file_flush`. I'm confident that the code has been structured to avoid uninitialized variable use. Now I'm systematically assessing the potential bug classes. I'm considering concurrency issues, race conditions involving cgroup enabling/disabling, workqueue flushes, and the lifetime management of the `cgrp` and `blkcg_wq` objects. I also contemplate potential deadlocks or UAF scenarios if work is queued when the workqueue is being destroyed. I'm aware that KASAN and LOCKDEP are excellent at catching these types of memory safety and synchronization errors. KMSAN would be redundant here, and would not catch them. Specifically, regarding KMSAN, I'm verifying that none of the four criteria for `NeedsKMSAN=true` are met: 1. There's no copying of potentially uninitialized kernel structures to user space. The configfs attribute uses a formatted `u64`, which is properly initialized, so no issues here. 2. There's no conditional logic that depends on uninitialized variables. All new variables are assigned a value before use. 3. There's no allocation of complex data structures where uninitialized fields could be read later. The `nvmet_ns` struct is allocated with `kzalloc_obj`, initializing all fields. 4. There's no bounds checks or logic that could lead to reading outside of initialized buffer boundaries. Therefore, my conclusion is that `NeedsKMSAN` is `false`. The existing KASAN and LOCKDEP tools in the kernel are fully equipped to catch any memory safety or synchronization problems. KMSAN's analysis is not needed here and would be unproductive. We're good to go.
38/3	2026/10/26 20:26	tool	set-results	0m Args: { "KMSANReasoning": "The patch adds cgroup-based I/O throttling support to NVMe target (nvmet) namespaces via configfs (`cgroup_id` attribute), dispatching I/O requests through dedicated per-namespace workqueues associated with the corresponding blkcg.\n\nFrom a memory safety perspective:\n1. All newly introduced struct members in `struct nvmet_ns` (`cgroup_id`, `cgrp`, `blkcg_wq`) are zero-initialized at allocation time via `kzalloc_obj()` in `nvmet_ns_alloc()`.\n2. The new configfs attribute show handler (`nvmet_ns_cgroup_id_show`) formats a scalar `u64` into an ASCII string using `snprintf()`, presenting no uninitialized padding or info-leak risk.\n3. In `nvmet_req`, the new fields (`blkcg_execute`, `blkcg_work`) are initialized via `INIT_WORK` and direct assignment during request handling when `ns-\u003ecgrp` is active, and local variables (`associated`, `status`, `noio_flag`) are explicitly assigned before use.\n4. Any potential issues with this patch relate to concurrency, lifetime management of the workqueue/cgroup reference across disable/enable operations, use-after-free, or locking dependencies, all of which are covered by KASAN and LOCKDEP.\n\nThere are no uninitialized memory reads or kernel info-leaks, so a dedicated KMSAN session is not warranted.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch adds cgroup-based I/O throttling support to NVMe target (nvmet) namespaces via configfs (`cgroup_id` attribute), dispatching I/O requests through dedicated per-namespace workqueues associated with the corresponding blkcg.\n\nFrom a memory safety perspective:\n1. All newly introduced struct members in `struct nvmet_ns` (`cgroup_id`, `cgrp`, `blkcg_wq`) are zero-initialized at allocation time via `kzalloc_obj()` in `nvmet_ns_alloc()`.\n2. The new configfs attribute show handler (`nvmet_ns_cgroup_id_show`) formats a scalar `u64` into an ASCII string using `snprintf()`, presenting no uninitialized padding or info-leak risk.\n3. In `nvmet_req`, the new fields (`blkcg_execute`, `blkcg_work`) are initialized via `INIT_WORK` and direct assignment during request handling when `ns-\u003ecgrp` is active, and local variables (`associated`, `status`, `noio_flag`) are explicitly assigned before use.\n4. Any potential issues with this patch relate to concurrency, lifetime management of the workqueue/cgroup reference across disable/enable operations, use-after-free, or locking dependencies, all of which are covered by KASAN and LOCKDEP.\n\nThere are no uninitialized memory reads or kernel info-leaks, so a dedicated KMSAN session is not warranted.", "NeedsKMSAN": false }

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