AI Trajectory

null

{
  "EnableConfigs": null,
  "FocusSymbols": [
    "iput_memalloc",
    "super_defer_iput",
    "super_deferred_iput_work",
    "super_deferred_iput_shutdown"
  ],
  "KMSANReasoning": "The patch introduces a mechanism to defer `iput()` calls from memory reclaim contexts (`PF_MEMALLOC`) to a dedicated workqueue (`super_deferred_iput_wq`). This is done to avoid blocking on `sync_lazytime()` during memory allocation. The changes involve adding new fields to `struct super_block` (which are properly initialized in `super_deferred_iput_init()`), list manipulations using `inode-\u003ei_lru`, and workqueue scheduling.\n\nThese modifications do not interact with user space boundaries (e.g., `copy_to_user`), do not introduce new complex data structures with potentially uninitialized fields, and do not alter bounds checking or data length calculations. Any potential bugs introduced by this patch would likely manifest as use-after-free, NULL pointer dereferences, or locking deadlocks (e.g., if the workqueue or list operations are mishandled). These types of issues are effectively detected by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch introduces a deferred iput mechanism for inodes during memory reclaim (PF_MEMALLOC context). This is a core VFS change affecting inode lifecycle and memory management, which can lead to use-after-free or memory leaks if not handled correctly.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 7197beca4c235dd7cb165f354c75f082d6927d1d\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Aug 13 10:51:19 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/fs/dcache.c b/fs/dcache.c\nindex 3e9af9de70746..5465d8dbfdd23 100644\n--- a/fs/dcache.c\n+++ b/fs/dcache.c\n@@ -3511,6 +3511,7 @@ void __init vfs_caches_init(void)\n {\n \tfilename_init();\n \tdcache_init();\n+\tsuper_init();\n \tinode_init();\n \tfiles_init();\n \tfiles_maxfiles_init();\ndiff --git a/fs/inode.c b/fs/inode.c\nindex 31c5b9ee3a81d..e71750bf7c82c 100644\n--- a/fs/inode.c\n+++ b/fs/inode.c\n@@ -18,6 +18,7 @@\n #include \u003clinux/mount.h\u003e\n #include \u003clinux/posix_acl.h\u003e\n #include \u003clinux/ratelimit.h\u003e\n+#include \u003clinux/sched.h\u003e\n #include \u003clinux/list_lru.h\u003e\n #include \u003clinux/iversion.h\u003e\n #include \u003clinux/rw_hint.h\u003e\n@@ -35,7 +36,7 @@\n  * inode-\u003ei_lock protects:\n  *   inode-\u003ei_state, inode-\u003ei_hash, __iget(), inode-\u003ei_io_list\n  * Inode LRU list locks protect:\n- *   inode-\u003ei_sb-\u003es_inode_lru, inode-\u003ei_lru\n+ *   inode-\u003ei_sb-\u003es_inode_lru, inode-\u003ei_lru when on the inode LRU\n  * inode-\u003ei_sb-\u003es_inode_list_lock protects:\n  *   inode-\u003ei_sb-\u003es_inodes, inode-\u003ei_sb_list\n  * bdi-\u003ewb.list_lock protects:\n@@ -2019,6 +2020,43 @@ static void iput_final(struct inode *inode)\n \tevict(inode);\n }\n \n+/* Like iput(), but defer sync_lazytime(). Used in reclaim paths. */\n+static void iput_memalloc(struct inode *inode)\n+{\n+\tspin_lock(\u0026inode-\u003ei_lock);\n+\tif (unlikely((inode_state_read(inode) \u0026 I_DIRTY_TIME) \u0026\u0026\n+\t\t     inode-\u003ei_nlink)) {\n+\t\tint ret;\n+\n+\t\tif (atomic_add_unless(\u0026inode-\u003ei_count, -1, 1)) {\n+\t\t\tspin_unlock(\u0026inode-\u003ei_lock);\n+\t\t\treturn;\n+\t\t}\n+\n+\t\tinode_lru_list_del(inode);\n+\t\tspin_unlock(\u0026inode-\u003ei_lock);\n+\n+\t\tret = super_defer_iput(inode);\n+\t\tif (!ret)\n+\t\t\treturn;\n+\n+\t\t/*\n+\t\t * The superblock is no longer accepting deferred iputs.\n+\t\t * This shouldn't happen.\n+\t\t */\n+\t\tWARN_ON_ONCE(ret == -ESHUTDOWN);\n+\t\tspin_lock(\u0026inode-\u003ei_lock);\n+\t\tinode_state_clear(inode, I_DIRTY_TIME);\n+\t}\n+\n+\tif (!atomic_dec_and_test(\u0026inode-\u003ei_count)) {\n+\t\tspin_unlock(\u0026inode-\u003ei_lock);\n+\t\treturn;\n+\t}\n+\n+\tiput_final(inode);\n+}\n+\n /**\n  *\tiput\t- put an inode\n  *\t@inode: inode to put\n@@ -2047,6 +2085,11 @@ void iput(struct inode *inode)\n \tif (atomic_add_unless(\u0026inode-\u003ei_count, -1, 1))\n \t\treturn;\n \n+\tif (unlikely(current-\u003eflags \u0026 PF_MEMALLOC)) {\n+\t\tiput_memalloc(inode);\n+\t\treturn;\n+\t}\n+\n \tif (inode-\u003ei_nlink \u0026\u0026 sync_lazytime(inode))\n \t\tgoto retry;\n \ndiff --git a/fs/internal.h b/fs/internal.h\nindex 355d93f922086..641b9a0c612d4 100644\n--- a/fs/internal.h\n+++ b/fs/internal.h\n@@ -9,6 +9,7 @@ struct super_block;\n struct file_system_type;\n struct iomap;\n struct iomap_ops;\n+struct inode;\n struct linux_binprm;\n struct path;\n struct mount;\n@@ -138,6 +139,8 @@ extern bool super_trylock_shared(struct super_block *sb);\n struct super_block *user_get_super(dev_t, bool excl);\n void put_super(struct super_block *sb);\n extern bool mount_capable(struct fs_context *);\n+void __init super_init(void);\n+int super_defer_iput(struct inode *inode);\n \n /*\n  * Prepare superblock for changing its read-only state (i.e., either remount\ndiff --git a/fs/super.c b/fs/super.c\nindex a8fd61136aafe..2f318694c98b4 100644\n--- a/fs/super.c\n+++ b/fs/super.c\n@@ -37,6 +37,7 @@\n #include \u003clinux/user_namespace.h\u003e\n #include \u003clinux/fs_context.h\u003e\n #include \u003clinux/fserror.h\u003e\n+#include \u003clinux/workqueue.h\u003e\n #include \u003cuapi/linux/mount.h\u003e\n #include \"internal.h\"\n \n@@ -45,6 +46,7 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who,\n \n static LIST_HEAD(super_blocks);\n static DEFINE_SPINLOCK(sb_lock);\n+static struct workqueue_struct *super_deferred_iput_wq __ro_after_init;\n \n static char *sb_writers_name[SB_FREEZE_LEVELS] = {\n \t\"sb_writers\",\n@@ -52,6 +54,89 @@ static char *sb_writers_name[SB_FREEZE_LEVELS] = {\n \t\"sb_internal\",\n };\n \n+/*\n+ * sb-\u003es_deferred_iput_lock protects sb-\u003es_deferred_iputs and inode-\u003ei_lru\n+ * while the inode is queued there.\n+ */\n+static void super_deferred_iput_work(struct work_struct *work)\n+{\n+\tstruct super_block *sb = container_of(work, struct super_block,\n+\t\t\t\t\t      s_deferred_iput_work);\n+\tLIST_HEAD(pending);\n+\n+\tfor (;;) {\n+\t\tspin_lock(\u0026sb-\u003es_deferred_iput_lock);\n+\t\tlist_splice_init(\u0026sb-\u003es_deferred_iputs, \u0026pending);\n+\t\tspin_unlock(\u0026sb-\u003es_deferred_iput_lock);\n+\n+\t\tif (list_empty(\u0026pending))\n+\t\t\tbreak;\n+\n+\t\twhile (!list_empty(\u0026pending)) {\n+\t\t\tstruct inode *inode;\n+\n+\t\t\tinode = list_first_entry(\u0026pending, struct inode, i_lru);\n+\t\t\tlist_del_init(\u0026inode-\u003ei_lru);\n+\t\t\tiput(inode);\n+\t\t\tcond_resched();\n+\t\t}\n+\t}\n+}\n+\n+static void __init super_deferred_iput_wq_init(void)\n+{\n+\tsuper_deferred_iput_wq = alloc_workqueue(\"super_deferred_iput\",\n+\t\t\t\t\t\t WQ_UNBOUND | WQ_MEM_RECLAIM, 0);\n+\tif (!super_deferred_iput_wq)\n+\t\tpanic(\"Failed to allocate super deferred iput workqueue\\n\");\n+}\n+\n+void __init super_init(void)\n+{\n+\tsuper_deferred_iput_wq_init();\n+}\n+\n+static void super_deferred_iput_init(struct super_block *sb)\n+{\n+\tspin_lock_init(\u0026sb-\u003es_deferred_iput_lock);\n+\tINIT_LIST_HEAD(\u0026sb-\u003es_deferred_iputs);\n+\tINIT_WORK(\u0026sb-\u003es_deferred_iput_work, super_deferred_iput_work);\n+\tsb-\u003es_deferred_iput_shutdown = false;\n+}\n+\n+static void super_deferred_iput_shutdown(struct super_block *sb)\n+{\n+\tbool empty;\n+\n+\tspin_lock(\u0026sb-\u003es_deferred_iput_lock);\n+\tsb-\u003es_deferred_iput_shutdown = true;\n+\tspin_unlock(\u0026sb-\u003es_deferred_iput_lock);\n+\n+\tflush_work(\u0026sb-\u003es_deferred_iput_work);\n+\n+\tspin_lock(\u0026sb-\u003es_deferred_iput_lock);\n+\tempty = list_empty(\u0026sb-\u003es_deferred_iputs);\n+\tspin_unlock(\u0026sb-\u003es_deferred_iput_lock);\n+\tWARN_ON_ONCE(!empty);\n+}\n+\n+int super_defer_iput(struct inode *inode)\n+{\n+\tstruct super_block *sb = inode-\u003ei_sb;\n+\tint ret = -ESHUTDOWN;\n+\n+\tspin_lock(\u0026sb-\u003es_deferred_iput_lock);\n+\tif (!sb-\u003es_deferred_iput_shutdown) {\n+\t\tlist_add_tail(\u0026inode-\u003ei_lru, \u0026sb-\u003es_deferred_iputs);\n+\t\t/* Queue under the lock so shutdown cannot miss this work. */\n+\t\tqueue_work(super_deferred_iput_wq, \u0026sb-\u003es_deferred_iput_work);\n+\t\tret = 0;\n+\t}\n+\tspin_unlock(\u0026sb-\u003es_deferred_iput_lock);\n+\n+\treturn ret;\n+}\n+\n static inline void __super_lock(struct super_block *sb, bool excl)\n {\n \tif (excl)\n@@ -363,6 +448,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,\n \tmutex_init(\u0026s-\u003es_sync_lock);\n \tINIT_LIST_HEAD(\u0026s-\u003es_inodes);\n \tspin_lock_init(\u0026s-\u003es_inode_list_lock);\n+\tsuper_deferred_iput_init(s);\n \tINIT_LIST_HEAD(\u0026s-\u003es_inodes_wb);\n \tspin_lock_init(\u0026s-\u003es_inode_wblist_lock);\n \tfserror_mount(s);\n@@ -474,6 +560,12 @@ void deactivate_locked_super(struct super_block *s)\n \tstruct file_system_type *fs = s-\u003es_type;\n \tif (atomic_dec_and_test(\u0026s-\u003es_active)) {\n \t\tshrinker_free(s-\u003es_shrink);\n+\t\t/*\n+\t\t * The shrinker can leave final inode references queued for\n+\t\t * processing outside reclaim. Drain them before\n+\t\t * filesystem-specific shutdown starts.\n+\t\t */\n+\t\tsuper_deferred_iput_shutdown(s);\n \t\tfs-\u003ekill_sb(s);\n \n \t\tkill_super_notify(s);\ndiff --git a/include/linux/fs/super_types.h b/include/linux/fs/super_types.h\nindex ef7941e9dc79a..9bd4abbdbd51b 100644\n--- a/include/linux/fs/super_types.h\n+++ b/include/linux/fs/super_types.h\n@@ -255,6 +255,12 @@ struct super_block {\n \t */\n \tstruct list_lru\t\t\t\ts_dentry_lru;\n \tstruct list_lru\t\t\t\ts_inode_lru;\n+\t/* Protects s_deferred_iputs and s_deferred_iput_shutdown. */\n+\tspinlock_t\t\t\t\ts_deferred_iput_lock;\n+\t/* Inodes whose final iput was deferred from PF_MEMALLOC context. */\n+\tstruct list_head\t\t\ts_deferred_iputs;\n+\tstruct work_struct\t\t\ts_deferred_iput_work;\n+\tbool\t\t\t\t\ts_deferred_iput_shutdown;\n \tstruct rcu_head\t\t\t\trcu;\n \tstruct work_struct\t\t\tdestroy_work;\n \n"
}

best-expensive

null

{
  "EnableConfigs": null,
  "FocusSymbols": [
    "iput_memalloc",
    "super_defer_iput",
    "super_deferred_iput_work",
    "super_deferred_iput_shutdown"
  ],
  "Reasoning": "The patch introduces a deferred iput mechanism for inodes during memory reclaim (PF_MEMALLOC context). This is a core VFS change affecting inode lifecycle and memory management, which can lead to use-after-free or memory leaks if not handled correctly.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
  even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs
   output array, and DO NOT add a '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.

For your convenience, here is the diff of the changes:
commit 7197beca4c235dd7cb165f354c75f082d6927d1d
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Aug 13 10:51:19 2026 +0000

    syz-cluster: applied patch under review

diff --git a/fs/dcache.c b/fs/dcache.c
index 3e9af9de70746..5465d8dbfdd23 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3511,6 +3511,7 @@ void __init vfs_caches_init(void)
 {
 	filename_init();
 	dcache_init();
+	super_init();
 	inode_init();
 	files_init();
 	files_maxfiles_init();
diff --git a/fs/inode.c b/fs/inode.c
index 31c5b9ee3a81d..e71750bf7c82c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -18,6 +18,7 @@
 #include <linux/mount.h>
 #include <linux/posix_acl.h>
 #include <linux/ratelimit.h>
+#include <linux/sched.h>
 #include <linux/list_lru.h>
 #include <linux/iversion.h>
 #include <linux/rw_hint.h>
@@ -35,7 +36,7 @@
  * inode->i_lock protects:
  *   inode->i_state, inode->i_hash, __iget(), inode->i_io_list
  * Inode LRU list locks protect:
- *   inode->i_sb->s_inode_lru, inode->i_lru
+ *   inode->i_sb->s_inode_lru, inode->i_lru when on the inode LRU
  * inode->i_sb->s_inode_list_lock protects:
  *   inode->i_sb->s_inodes, inode->i_sb_list
  * bdi->wb.list_lock protects:
@@ -2019,6 +2020,43 @@ static void iput_final(struct inode *inode)
 	evict(inode);
 }
 
+/* Like iput(), but defer sync_lazytime(). Used in reclaim paths. */
+static void iput_memalloc(struct inode *inode)
+{
+	spin_lock(&inode->i_lock);
+	if (unlikely((inode_state_read(inode) & I_DIRTY_TIME) &&
+		     inode->i_nlink)) {
+		int ret;
+
+		if (atomic_add_unless(&inode->i_count, -1, 1)) {
+			spin_unlock(&inode->i_lock);
+			return;
+		}
+
+		inode_lru_list_del(inode);
+		spin_unlock(&inode->i_lock);
+
+		ret = super_defer_iput(inode);
+		if (!ret)
+			return;
+
+		/*
+		 * The superblock is no longer accepting deferred iputs.
+		 * This shouldn't happen.
+		 */
+		WARN_ON_ONCE(ret == -ESHUTDOWN);
+		spin_lock(&inode->i_lock);
+		inode_state_clear(inode, I_DIRTY_TIME);
+	}
+
+	if (!atomic_dec_and_test(&inode->i_count)) {
+		spin_unlock(&inode->i_lock);
+		return;
+	}
+
+	iput_final(inode);
+}
+
 /**
  *	iput	- put an inode
  *	@inode: inode to put
@@ -2047,6 +2085,11 @@ void iput(struct inode *inode)
 	if (atomic_add_unless(&inode->i_count, -1, 1))
 		return;
 
+	if (unlikely(current->flags & PF_MEMALLOC)) {
+		iput_memalloc(inode);
+		return;
+	}
+
 	if (inode->i_nlink && sync_lazytime(inode))
 		goto retry;
 
diff --git a/fs/internal.h b/fs/internal.h
index 355d93f922086..641b9a0c612d4 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -9,6 +9,7 @@ struct super_block;
 struct file_system_type;
 struct iomap;
 struct iomap_ops;
+struct inode;
 struct linux_binprm;
 struct path;
 struct mount;
@@ -138,6 +139,8 @@ extern bool super_trylock_shared(struct super_block *sb);
 struct super_block *user_get_super(dev_t, bool excl);
 void put_super(struct super_block *sb);
 extern bool mount_capable(struct fs_context *);
+void __init super_init(void);
+int super_defer_iput(struct inode *inode);
 
 /*
  * Prepare superblock for changing its read-only state (i.e., either remount
diff --git a/fs/super.c b/fs/super.c
index a8fd61136aafe..2f318694c98b4 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -37,6 +37,7 @@
 #include <linux/user_namespace.h>
 #include <linux/fs_context.h>
 #include <linux/fserror.h>
+#include <linux/workqueue.h>
 #include <uapi/linux/mount.h>
 #include "internal.h"
 
@@ -45,6 +46,7 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who,
 
 static LIST_HEAD(super_blocks);
 static DEFINE_SPINLOCK(sb_lock);
+static struct workqueue_struct *super_deferred_iput_wq __ro_after_init;
 
 static char *sb_writers_name[SB_FREEZE_LEVELS] = {
 	"sb_writers",
@@ -52,6 +54,89 @@ static char *sb_writers_name[SB_FREEZE_LEVELS] = {
 	"sb_internal",
 };
 
+/*
+ * sb->s_deferred_iput_lock protects sb->s_deferred_iputs and inode->i_lru
+ * while the inode is queued there.
+ */
+static void super_deferred_iput_work(struct work_struct *work)
+{
+	struct super_block *sb = container_of(work, struct super_block,
+					      s_deferred_iput_work);
+	LIST_HEAD(pending);
+
+	for (;;) {
+		spin_lock(&sb->s_deferred_iput_lock);
+		list_splice_init(&sb->s_deferred_iputs, &pending);
+		spin_unlock(&sb->s_deferred_iput_lock);
+
+		if (list_empty(&pending))
+			break;
+
+		while (!list_empty(&pending)) {
+			struct inode *inode;
+
+			inode = list_first_entry(&pending, struct inode, i_lru);
+			list_del_init(&inode->i_lru);
+			iput(inode);
+			cond_resched();
+		}
+	}
+}
+
+static void __init super_deferred_iput_wq_init(void)
+{
+	super_deferred_iput_wq = alloc_workqueue("super_deferred_iput",
+						 WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
+	if (!super_deferred_iput_wq)
+		panic("Failed to allocate super deferred iput workqueue\n");
+}
+
+void __init super_init(void)
+{
+	super_deferred_iput_wq_init();
+}
+
+static void super_deferred_iput_init(struct super_block *sb)
+{
+	spin_lock_init(&sb->s_deferred_iput_lock);
+	INIT_LIST_HEAD(&sb->s_deferred_iputs);
+	INIT_WORK(&sb->s_deferred_iput_work, super_deferred_iput_work);
+	sb->s_deferred_iput_shutdown = false;
+}
+
+static void super_deferred_iput_shutdown(struct super_block *sb)
+{
+	bool empty;
+
+	spin_lock(&sb->s_deferred_iput_lock);
+	sb->s_deferred_iput_shutdown = true;
+	spin_unlock(&sb->s_deferred_iput_lock);
+
+	flush_work(&sb->s_deferred_iput_work);
+
+	spin_lock(&sb->s_deferred_iput_lock);
+	empty = list_empty(&sb->s_deferred_iputs);
+	spin_unlock(&sb->s_deferred_iput_lock);
+	WARN_ON_ONCE(!empty);
+}
+
+int super_defer_iput(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	int ret = -ESHUTDOWN;
+
+	spin_lock(&sb->s_deferred_iput_lock);
+	if (!sb->s_deferred_iput_shutdown) {
+		list_add_tail(&inode->i_lru, &sb->s_deferred_iputs);
+		/* Queue under the lock so shutdown cannot miss this work. */
+		queue_work(super_deferred_iput_wq, &sb->s_deferred_iput_work);
+		ret = 0;
+	}
+	spin_unlock(&sb->s_deferred_iput_lock);
+
+	return ret;
+}
+
 static inline void __super_lock(struct super_block *sb, bool excl)
 {
 	if (excl)
@@ -363,6 +448,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	mutex_init(&s->s_sync_lock);
 	INIT_LIST_HEAD(&s->s_inodes);
 	spin_lock_init(&s->s_inode_list_lock);
+	super_deferred_iput_init(s);
 	INIT_LIST_HEAD(&s->s_inodes_wb);
 	spin_lock_init(&s->s_inode_wblist_lock);
 	fserror_mount(s);
@@ -474,6 +560,12 @@ void deactivate_locked_super(struct super_block *s)
 	struct file_system_type *fs = s->s_type;
 	if (atomic_dec_and_test(&s->s_active)) {
 		shrinker_free(s->s_shrink);
+		/*
+		 * The shrinker can leave final inode references queued for
+		 * processing outside reclaim. Drain them before
+		 * filesystem-specific shutdown starts.
+		 */
+		super_deferred_iput_shutdown(s);
 		fs->kill_sb(s);
 
 		kill_super_notify(s);
diff --git a/include/linux/fs/super_types.h b/include/linux/fs/super_types.h
index ef7941e9dc79a..9bd4abbdbd51b 100644
--- a/include/linux/fs/super_types.h
+++ b/include/linux/fs/super_types.h
@@ -255,6 +255,12 @@ struct super_block {
 	 */
 	struct list_lru				s_dentry_lru;
 	struct list_lru				s_inode_lru;
+	/* Protects s_deferred_iputs and s_deferred_iput_shutdown. */
+	spinlock_t				s_deferred_iput_lock;
+	/* Inodes whose final iput was deferred from PF_MEMALLOC context. */
+	struct list_head			s_deferred_iputs;
+	struct work_struct			s_deferred_iput_work;
+	bool					s_deferred_iput_shutdown;
 	struct rcu_head				rcu;
 	struct work_struct			destroy_work;
 

gemini-3.1-pro-preview

null

null

							input: 4865
							output: 120
							thoughts: 824
						

**Fuzzing Plan: Deferred `iput()` in Memory Reclaim**

Okay, so this patch is interesting. It's introducing a mechanism to defer `iput()` calls specifically when they're triggered from a context where `PF_MEMALLOC` is set, meaning memory reclaim is happening. That's a key point – we're talking core VFS modifications, directly impacting how inodes are managed during memory-critical situations. This is definitely worth a deep dive for fuzzing.

The approach is to add a new function, `iput_memalloc()`, which intelligently defers the final `iput` to a workqueue (`super_deferred_iput_wq`) if the inode has `I_DIRTY_TIME` set and has a positive link count. The workqueue then handles the actual delayed `iput` operation. This makes the `iput` path less hot, which is good. We’re on a slower path when `PF_MEMALLOC` is set and `iput_memalloc` is called.

My focus has to be on the interplay between the regular `iput` path and this new deferred path. The critical areas are:

*   `iput_memalloc` - This is where the deferral logic is implemented.
*   `super_defer_iput` - This is the primary function for deferring the `iput`.
*   `super_deferred_iput_work` - The workqueue function that actually performs the delayed `iput`.
*   `super_deferred_iput_shutdown` - A shutdown function.

I initially thought about including `iput` as well, but it's a very hot path, so I'm omitting that. The patch modifies `iput`, but it's unlikely we'll get coverage if we include it in fuzzing. I did double-check whether `iput_memalloc` was static. While it is, and could possibly be inlined, it's called from a non-static `iput` which will still be interesting, so I'll include it.

Based on this analysis, I'm confident this is a worthwhile target for fuzzing. The patch is touching core VFS code and memory management, so any issues here could have significant consequences, especially during memory reclaim. Given that this is a core VFS change, no specific configurations should be needed.

I'm including:
- `iput_memalloc`
- `super_defer_iput`
- `super_deferred_iput_work`
- `super_deferred_iput_shutdown`

I'm ready to kick things off. Let's see what we can find.

{
  "EnableConfigs": [],
  "FocusSymbols": [
    "iput_memalloc",
    "super_defer_iput",
    "super_deferred_iput_work",
    "super_deferred_iput_shutdown"
  ],
  "Reasoning": "The patch introduces a deferred iput mechanism for inodes during memory reclaim (PF_MEMALLOC context). This is a core VFS change affecting inode lifecycle and memory management, which can lead to use-after-free or memory leaks if not handled correctly.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": null,
  "FocusSymbols": [
    "iput_memalloc",
    "super_defer_iput",
    "super_deferred_iput_work",
    "super_deferred_iput_shutdown"
  ],
  "Reasoning": "The patch introduces a deferred iput mechanism for inodes during memory reclaim (PF_MEMALLOC context). This is a core VFS change affecting inode lifecycle and memory management, which can lead to use-after-free or memory leaks if not handled correctly.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

best-expensive

null

{
  "KMSANReasoning": "The patch introduces a mechanism to defer `iput()` calls from memory reclaim contexts (`PF_MEMALLOC`) to a dedicated workqueue (`super_deferred_iput_wq`). This is done to avoid blocking on `sync_lazytime()` during memory allocation. The changes involve adding new fields to `struct super_block` (which are properly initialized in `super_deferred_iput_init()`), list manipulations using `inode-\u003ei_lru`, and workqueue scheduling.\n\nThese modifications do not interact with user space boundaries (e.g., `copy_to_user`), do not introduce new complex data structures with potentially uninitialized fields, and do not alter bounds checking or data length calculations. Any potential bugs introduced by this patch would likely manifest as use-after-free, NULL pointer dereferences, or locking deadlocks (e.g., if the workqueue or list operations are mishandled). These types of issues are effectively detected by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.",
  "NeedsKMSAN": false
}

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.

For your convenience, here is the diff of the changes:
commit 7197beca4c235dd7cb165f354c75f082d6927d1d
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Aug 13 10:51:19 2026 +0000

    syz-cluster: applied patch under review

diff --git a/fs/dcache.c b/fs/dcache.c
index 3e9af9de70746..5465d8dbfdd23 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3511,6 +3511,7 @@ void __init vfs_caches_init(void)
 {
 	filename_init();
 	dcache_init();
+	super_init();
 	inode_init();
 	files_init();
 	files_maxfiles_init();
diff --git a/fs/inode.c b/fs/inode.c
index 31c5b9ee3a81d..e71750bf7c82c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -18,6 +18,7 @@
 #include <linux/mount.h>
 #include <linux/posix_acl.h>
 #include <linux/ratelimit.h>
+#include <linux/sched.h>
 #include <linux/list_lru.h>
 #include <linux/iversion.h>
 #include <linux/rw_hint.h>
@@ -35,7 +36,7 @@
  * inode->i_lock protects:
  *   inode->i_state, inode->i_hash, __iget(), inode->i_io_list
  * Inode LRU list locks protect:
- *   inode->i_sb->s_inode_lru, inode->i_lru
+ *   inode->i_sb->s_inode_lru, inode->i_lru when on the inode LRU
  * inode->i_sb->s_inode_list_lock protects:
  *   inode->i_sb->s_inodes, inode->i_sb_list
  * bdi->wb.list_lock protects:
@@ -2019,6 +2020,43 @@ static void iput_final(struct inode *inode)
 	evict(inode);
 }
 
+/* Like iput(), but defer sync_lazytime(). Used in reclaim paths. */
+static void iput_memalloc(struct inode *inode)
+{
+	spin_lock(&inode->i_lock);
+	if (unlikely((inode_state_read(inode) & I_DIRTY_TIME) &&
+		     inode->i_nlink)) {
+		int ret;
+
+		if (atomic_add_unless(&inode->i_count, -1, 1)) {
+			spin_unlock(&inode->i_lock);
+			return;
+		}
+
+		inode_lru_list_del(inode);
+		spin_unlock(&inode->i_lock);
+
+		ret = super_defer_iput(inode);
+		if (!ret)
+			return;
+
+		/*
+		 * The superblock is no longer accepting deferred iputs.
+		 * This shouldn't happen.
+		 */
+		WARN_ON_ONCE(ret == -ESHUTDOWN);
+		spin_lock(&inode->i_lock);
+		inode_state_clear(inode, I_DIRTY_TIME);
+	}
+
+	if (!atomic_dec_and_test(&inode->i_count)) {
+		spin_unlock(&inode->i_lock);
+		return;
+	}
+
+	iput_final(inode);
+}
+
 /**
  *	iput	- put an inode
  *	@inode: inode to put
@@ -2047,6 +2085,11 @@ void iput(struct inode *inode)
 	if (atomic_add_unless(&inode->i_count, -1, 1))
 		return;
 
+	if (unlikely(current->flags & PF_MEMALLOC)) {
+		iput_memalloc(inode);
+		return;
+	}
+
 	if (inode->i_nlink && sync_lazytime(inode))
 		goto retry;
 
diff --git a/fs/internal.h b/fs/internal.h
index 355d93f922086..641b9a0c612d4 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -9,6 +9,7 @@ struct super_block;
 struct file_system_type;
 struct iomap;
 struct iomap_ops;
+struct inode;
 struct linux_binprm;
 struct path;
 struct mount;
@@ -138,6 +139,8 @@ extern bool super_trylock_shared(struct super_block *sb);
 struct super_block *user_get_super(dev_t, bool excl);
 void put_super(struct super_block *sb);
 extern bool mount_capable(struct fs_context *);
+void __init super_init(void);
+int super_defer_iput(struct inode *inode);
 
 /*
  * Prepare superblock for changing its read-only state (i.e., either remount
diff --git a/fs/super.c b/fs/super.c
index a8fd61136aafe..2f318694c98b4 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -37,6 +37,7 @@
 #include <linux/user_namespace.h>
 #include <linux/fs_context.h>
 #include <linux/fserror.h>
+#include <linux/workqueue.h>
 #include <uapi/linux/mount.h>
 #include "internal.h"
 
@@ -45,6 +46,7 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who,
 
 static LIST_HEAD(super_blocks);
 static DEFINE_SPINLOCK(sb_lock);
+static struct workqueue_struct *super_deferred_iput_wq __ro_after_init;
 
 static char *sb_writers_name[SB_FREEZE_LEVELS] = {
 	"sb_writers",
@@ -52,6 +54,89 @@ static char *sb_writers_name[SB_FREEZE_LEVELS] = {
 	"sb_internal",
 };
 
+/*
+ * sb->s_deferred_iput_lock protects sb->s_deferred_iputs and inode->i_lru
+ * while the inode is queued there.
+ */
+static void super_deferred_iput_work(struct work_struct *work)
+{
+	struct super_block *sb = container_of(work, struct super_block,
+					      s_deferred_iput_work);
+	LIST_HEAD(pending);
+
+	for (;;) {
+		spin_lock(&sb->s_deferred_iput_lock);
+		list_splice_init(&sb->s_deferred_iputs, &pending);
+		spin_unlock(&sb->s_deferred_iput_lock);
+
+		if (list_empty(&pending))
+			break;
+
+		while (!list_empty(&pending)) {
+			struct inode *inode;
+
+			inode = list_first_entry(&pending, struct inode, i_lru);
+			list_del_init(&inode->i_lru);
+			iput(inode);
+			cond_resched();
+		}
+	}
+}
+
+static void __init super_deferred_iput_wq_init(void)
+{
+	super_deferred_iput_wq = alloc_workqueue("super_deferred_iput",
+						 WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
+	if (!super_deferred_iput_wq)
+		panic("Failed to allocate super deferred iput workqueue\n");
+}
+
+void __init super_init(void)
+{
+	super_deferred_iput_wq_init();
+}
+
+static void super_deferred_iput_init(struct super_block *sb)
+{
+	spin_lock_init(&sb->s_deferred_iput_lock);
+	INIT_LIST_HEAD(&sb->s_deferred_iputs);
+	INIT_WORK(&sb->s_deferred_iput_work, super_deferred_iput_work);
+	sb->s_deferred_iput_shutdown = false;
+}
+
+static void super_deferred_iput_shutdown(struct super_block *sb)
+{
+	bool empty;
+
+	spin_lock(&sb->s_deferred_iput_lock);
+	sb->s_deferred_iput_shutdown = true;
+	spin_unlock(&sb->s_deferred_iput_lock);
+
+	flush_work(&sb->s_deferred_iput_work);
+
+	spin_lock(&sb->s_deferred_iput_lock);
+	empty = list_empty(&sb->s_deferred_iputs);
+	spin_unlock(&sb->s_deferred_iput_lock);
+	WARN_ON_ONCE(!empty);
+}
+
+int super_defer_iput(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	int ret = -ESHUTDOWN;
+
+	spin_lock(&sb->s_deferred_iput_lock);
+	if (!sb->s_deferred_iput_shutdown) {
+		list_add_tail(&inode->i_lru, &sb->s_deferred_iputs);
+		/* Queue under the lock so shutdown cannot miss this work. */
+		queue_work(super_deferred_iput_wq, &sb->s_deferred_iput_work);
+		ret = 0;
+	}
+	spin_unlock(&sb->s_deferred_iput_lock);
+
+	return ret;
+}
+
 static inline void __super_lock(struct super_block *sb, bool excl)
 {
 	if (excl)
@@ -363,6 +448,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	mutex_init(&s->s_sync_lock);
 	INIT_LIST_HEAD(&s->s_inodes);
 	spin_lock_init(&s->s_inode_list_lock);
+	super_deferred_iput_init(s);
 	INIT_LIST_HEAD(&s->s_inodes_wb);
 	spin_lock_init(&s->s_inode_wblist_lock);
 	fserror_mount(s);
@@ -474,6 +560,12 @@ void deactivate_locked_super(struct super_block *s)
 	struct file_system_type *fs = s->s_type;
 	if (atomic_dec_and_test(&s->s_active)) {
 		shrinker_free(s->s_shrink);
+		/*
+		 * The shrinker can leave final inode references queued for
+		 * processing outside reclaim. Drain them before
+		 * filesystem-specific shutdown starts.
+		 */
+		super_deferred_iput_shutdown(s);
 		fs->kill_sb(s);
 
 		kill_super_notify(s);
diff --git a/include/linux/fs/super_types.h b/include/linux/fs/super_types.h
index ef7941e9dc79a..9bd4abbdbd51b 100644
--- a/include/linux/fs/super_types.h
+++ b/include/linux/fs/super_types.h
@@ -255,6 +255,12 @@ struct super_block {
 	 */
 	struct list_lru				s_dentry_lru;
 	struct list_lru				s_inode_lru;
+	/* Protects s_deferred_iputs and s_deferred_iput_shutdown. */
+	spinlock_t				s_deferred_iput_lock;
+	/* Inodes whose final iput was deferred from PF_MEMALLOC context. */
+	struct list_head			s_deferred_iputs;
+	struct work_struct			s_deferred_iput_work;
+	bool					s_deferred_iput_shutdown;
 	struct rcu_head				rcu;
 	struct work_struct			destroy_work;
 

gemini-3.1-pro-preview

null

null

							input: 4862
							output: 250
							thoughts: 807
						

**KMSAN Fuzzing Session Assessment**

Okay, let's break this down. We need to decide if this patch series warrants a dedicated KMSAN fuzzing session. My initial impression is...no, but let's confirm.

The patch aims to improve memory reclaim by deferring `iput()` operations within a memory allocation context (`PF_MEMALLOC`).  Specifically, it introduces `iput_memalloc()` which intelligently offloads the `iput()` to a workqueue (`super_deferred_iput_wq`) under specific conditions: the inode has `I_DIRTY_TIME` and `i_nlink > 0`. This avoids potential blocking issues during reclaim, particularly with `sync_lazytime()`.

Looking at the code changes, we see modifications across several files: `fs/dcache.c`, `fs/inode.c`, `fs/internal.h`, `fs/super.c`, and `include/linux/fs/super_types.h`.  It looks like a well-contained change within the VFS layer, with an emphasis on deferring I/O related operations. There's the addition of a workqueue, some structures in `struct super_block`, and associated initialization and cleanup functions.

My concern is always around memory safety: uninitialized memory usage or information leaks.  I need to check for those. It looks like the inodes are queued using `inode->i_lru` on `sb->s_deferred_iputs`. However, the structures added to `struct super_block` are properly initialized in `super_deferred_iput_init()`.  The workqueue is also initialized properly. Crucially, there's no interaction with user space, no complex data structures being constructed that could expose uninitialized fields.  The changes seem to be primarily focused on memory reclaim, locking, and workqueues, which are exactly the types of changes that KASAN and LOCKDEP are designed to catch bugs for.

Therefore, I'm confident that this patch *doesn't* introduce any significant risk of uninitialized memory usage or information leaks.  The potential bugs I see being introduced are things like use-after-free, null pointer dereferences, or locking issues like deadlocks.  These are exactly the kinds of problems that are typically caught by existing kernel sanitizers like KASAN and LOCKDEP.

Let's double check my analysis with the established rules:

We need to consider KMSAN if the patch:
1.  Touches Kernel structures sent to user space...Nope.
2.  Involves conditional logic based on potentially uninitialized variables...Nope.
3.  Allocates or initializes complex data structures where uninitialized fields could be read later...Nope.
4.  Modifies bounds checks, lengths, or logic that enables access to uninitialized memory...Nope.

Otherwise, we don't. This patch:
- Risks out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs... Yes, but those are covered by existing kernel tools.
- Initializes all touched stack/heap structures... Yes.
- Doesn't introduce uninitialized memory risks or info-leaks... Yes.

This patch series is strictly about deferring an `iput()` operation to avoid blocking in a memory allocation context. It does not interface with userspace and doesn't do complex memory manipulation that could allow uninitialized memory to be leaked.

**Therefore, I'll set `NeedsKMSAN=false` and provide this reasoning.**

{
  "KMSANReasoning": "The patch introduces a mechanism to defer `iput()` calls from memory reclaim contexts (`PF_MEMALLOC`) to a dedicated workqueue (`super_deferred_iput_wq`). This is done to avoid blocking on `sync_lazytime()` during memory allocation. The changes involve adding new fields to `struct super_block` (which are properly initialized in `super_deferred_iput_init()`), list manipulations using `inode-\u003ei_lru`, and workqueue scheduling.\n\nThese modifications do not interact with user space boundaries (e.g., `copy_to_user`), do not introduce new complex data structures with potentially uninitialized fields, and do not alter bounds checking or data length calculations. Any potential bugs introduced by this patch would likely manifest as use-after-free, NULL pointer dereferences, or locking deadlocks (e.g., if the workqueue or list operations are mishandled). These types of issues are effectively detected by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch introduces a mechanism to defer `iput()` calls from memory reclaim contexts (`PF_MEMALLOC`) to a dedicated workqueue (`super_deferred_iput_wq`). This is done to avoid blocking on `sync_lazytime()` during memory allocation. The changes involve adding new fields to `struct super_block` (which are properly initialized in `super_deferred_iput_init()`), list manipulations using `inode-\u003ei_lru`, and workqueue scheduling.\n\nThese modifications do not interact with user space boundaries (e.g., `copy_to_user`), do not introduce new complex data structures with potentially uninitialized fields, and do not alter bounds checking or data length calculations. Any potential bugs introduced by this patch would likely manifest as use-after-free, NULL pointer dereferences, or locking deadlocks (e.g., if the workqueue or list operations are mishandled). These types of issues are effectively detected by standard KASAN and LOCKDEP. There is no risk of uninitialized memory usage or info-leaks that would require KMSAN.",
  "NeedsKMSAN": false
}