FAILED: patch "[PATCH] nfsd: fix fcache_disposal UAF by inlining dispose state into" failed to apply to 6.12-stable tree

PATCH In review [email protected] 3 participants 3 messages Sep 3 – Sep 17

Subsystems (2)

Stable branch NFS server

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[email protected]

author maintainer

2026-09-03 13:39 UTC #0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090339-quarry-bottom-b4e0@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4 Mon Sep 17 00:00:00 2001
From: Jeff Layton <[email protected]>
Date: Tue, 2 Jun 2026 12:23:19 -0400
Subject: [PATCH] nfsd: fix fcache_disposal UAF by inlining dispose state into
nfsd_net

nfsd_file_dispose_list_delayed() defers fput() to nfsd service threads via a per-net freeme queue, preventing the shrinker and GC worker from bearing the cost of closing files (see ffb402596147). However, the queue lives in a separately-allocated struct nfsd_fcache_disposal that is freed by nfsd_free_fcache_disposal_net() during per-net teardown. The global shrinker, laundrette, and fsnotify callbacks can still be inside nfsd_file_dispose_list_delayed() dereferencing that pointer, causing a use-after-free.

Inline the spinlock and freeme list directly into struct nfsd_net (as fcache_dispose_lock and fcache_dispose_list), eliminating the separately allocated struct nfsd_fcache_disposal entirely. These fields now have the same lifetime as the net namespace itself, so there is no dangling pointer to chase.

nfsd_file_cache_start_net() now just initializes the inline fields and cannot fail due to allocation. nfsd_file_cache_shutdown_net() drains the inline list directly instead of freeing a separate struct. The alloc/free helpers are removed.

Fixes 1463b38e7cf3 ("NFSD: simplify per-net file cache management")

Cc [email protected]

Assisted-by Claude:claude-opus-4-6

Signed-off-by Jeff Layton <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Chuck Lever <[email protected]>

fs/nfsd/filecache.c +22 ~~-55~~

index 19beb4d482be..da5a44c31acb 100644
@@ -62,11 +62,6 @@ static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);
 
-struct nfsd_fcache_disposal {
-	spinlock_t lock;
-	struct list_head freeme;
-};
-
 static struct kmem_cache		*nfsd_file_slab;
 static struct kmem_cache		*nfsd_file_mark_slab;
 static struct list_lru			nfsd_file_lru;

@@ -422,25 +417,25 @@ nfsd_file_dispose_list(struct list_head *dispose)
 }
 
 /**
- * nfsd_file_dispose_list_delayed - move list of dead files to net's freeme list
+ * nfsd_file_dispose_list_delayed - queue dead files for nfsd thread disposal
  * @dispose: list of nfsd_files to be disposed
  *
- * Transfers each file to the "freeme" list for its nfsd_net, to eventually
- * be disposed of by the per-net garbage collector.
+ * Transfers each file to the dispose list in its nfsd_net and wakes an nfsd
+ * thread to do the actual close.  This keeps the cost of fput() in the nfsd
+ * threads rather than in the shrinker or GC worker.
  */
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
-	while(!list_empty(dispose)) {
+	while (!list_empty(dispose)) {
 		struct nfsd_file *nf = list_first_entry(dispose,
 						struct nfsd_file, nf_gc);
 		struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
-		struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 		struct svc_serv *serv;
 
-		spin_lock(&l->lock);
-		list_move_tail(&nf->nf_gc, &l->freeme);
-		spin_unlock(&l->lock);
+		spin_lock(&nn->fcache_dispose_lock);
+		list_move_tail(&nf->nf_gc, &nn->fcache_dispose_list);
+		spin_unlock(&nn->fcache_dispose_lock);
 
 		/*
 		 * The filecache laundrette is shut down after the

@@ -464,17 +459,15 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose)
  */
 void nfsd_file_net_dispose(struct nfsd_net *nn)
 {
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	if (!list_empty(&l->freeme)) {
+	if (!list_empty(&nn->fcache_dispose_list)) {
 		LIST_HEAD(dispose);
 		int i;
 
-		spin_lock(&l->lock);
-		for (i = 0; i < 8 && !list_empty(&l->freeme); i++)
-			list_move(l->freeme.next, &dispose);
-		spin_unlock(&l->lock);
-		if (!list_empty(&l->freeme)) {
+		spin_lock(&nn->fcache_dispose_lock);
+		for (i = 0; i < 8 && !list_empty(&nn->fcache_dispose_list); i++)
+			list_move(nn->fcache_dispose_list.next, &dispose);
+		spin_unlock(&nn->fcache_dispose_lock);
+		if (!list_empty(&nn->fcache_dispose_list)) {
 			/*
 			 * Wake up another thread to share the work
 			 * *before* doing any actual disposing.

@@ -698,11 +691,11 @@ nfsd_file_queue_for_close(struct inode *inode, struct list_head *dispose)
 }
 
 /**
- * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
+ * nfsd_file_close_inode - attempt a deferred close of a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
  * Close out any open nfsd_files that can be reaped for @inode. The
- * actual freeing is deferred to the dispose_list_delayed infrastructure.
+ * actual freeing is deferred to the nfsd service threads.
  *
  * This is used by the fsnotify callbacks and setlease notifier.
  */

@@ -952,42 +945,14 @@ __nfsd_file_cache_purge(struct net *net)
 	nfsd_file_dispose_list(&dispose);
 }
 
-static struct nfsd_fcache_disposal *
-nfsd_alloc_fcache_disposal(void)
-{
-	struct nfsd_fcache_disposal *l;
-
-	l = kmalloc_obj(*l);
-	if (!l)
-		return NULL;
-	spin_lock_init(&l->lock);
-	INIT_LIST_HEAD(&l->freeme);
-	return l;
-}
-
-static void
-nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
-{
-	nfsd_file_dispose_list(&l->freeme);
-	kfree(l);
-}
-
-static void
-nfsd_free_fcache_disposal_net(struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	nfsd_free_fcache_disposal(l);
-}
-
 int
 nfsd_file_cache_start_net(struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
-	nn->fcache_disposal = nfsd_alloc_fcache_disposal();
-	return nn->fcache_disposal ? 0 : -ENOMEM;
+	spin_lock_init(&nn->fcache_dispose_lock);
+	INIT_LIST_HEAD(&nn->fcache_dispose_list);
+	return 0;
 }
 
 /**

@@ -1006,8 +971,10 @@ nfsd_file_cache_purge(struct net *net)
 void
 nfsd_file_cache_shutdown_net(struct net *net)
 {
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
 	nfsd_file_cache_purge(net);
-	nfsd_free_fcache_disposal_net(net);
+	nfsd_file_dispose_list(&nn->fcache_dispose_list);
 }
 
 void

fs/nfsd/netns.h +2 -1

index f6b8b340bf8e..5c33c96da28e 100644
@@ -216,7 +216,8 @@ struct nfsd_net {
 	/* utsname taken from the process that starts the server */
 	char			nfsd_name[UNX_MAXNODENAME+1];
 
-	struct nfsd_fcache_disposal *fcache_disposal;
+	spinlock_t		fcache_dispose_lock;
+	struct list_head	fcache_dispose_list;
 
 	siphash_key_t		siphash_key;

Sasha Levin

maintainer

2026-09-05 14:47 UTC #1 lore raw

PATCH 1/1 nfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net

From: Jeff Layton <[email protected]>

[ Upstream commit bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4 ]

Fixes 1463b38e7cf3 ("NFSD: simplify per-net file cache management")

Cc [email protected]

Assisted-by Claude:claude-opus-4-6

Signed-off-by Jeff Layton <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Chuck Lever <[email protected]>

[ adapted disposal-list references while retaining the older unguarded service wake-up flow and removing the legacy kmalloc()-based helper ]

Signed-off-by Sasha Levin <[email protected]>

---
 fs/nfsd/filecache.c | 77 +++++++++++++--------------------------------
 fs/nfsd/netns.h     |  3 +-
 2 files changed, 24 insertions(+), 56 deletions(-)

fs/nfsd/filecache.c +22 ~~-55~~

index 05f0a4867673d..4381d76e83c63 100644
@@ -61,11 +61,6 @@ static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);
 
-struct nfsd_fcache_disposal {
-	spinlock_t lock;
-	struct list_head freeme;
-};
-
 static struct kmem_cache		*nfsd_file_slab;
 static struct kmem_cache		*nfsd_file_mark_slab;
 static struct list_lru			nfsd_file_lru;

@@ -431,25 +426,25 @@ nfsd_file_dispose_list(struct list_head *dispose)
 }
 
 /**
- * nfsd_file_dispose_list_delayed - move list of dead files to net's freeme list
+ * nfsd_file_dispose_list_delayed - queue dead files for nfsd thread disposal
  * @dispose: list of nfsd_files to be disposed
  *
- * Transfers each file to the "freeme" list for its nfsd_net, to eventually
- * be disposed of by the per-net garbage collector.
+ * Transfers each file to the dispose list in its nfsd_net and wakes an nfsd
+ * thread to do the actual close.  This keeps the cost of fput() in the nfsd
+ * threads rather than in the shrinker or GC worker.
  */
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
-	while(!list_empty(dispose)) {
+	while (!list_empty(dispose)) {
 		struct nfsd_file *nf = list_first_entry(dispose,
 						struct nfsd_file, nf_gc);
 		struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
-		struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 		struct svc_serv *serv;
 
-		spin_lock(&l->lock);
-		list_move_tail(&nf->nf_gc, &l->freeme);
-		spin_unlock(&l->lock);
+		spin_lock(&nn->fcache_dispose_lock);
+		list_move_tail(&nf->nf_gc, &nn->fcache_dispose_list);
+		spin_unlock(&nn->fcache_dispose_lock);
 
 		/*
 		 * The filecache laundrette is shut down after the

@@ -473,17 +468,15 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose)
  */
 void nfsd_file_net_dispose(struct nfsd_net *nn)
 {
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	if (!list_empty(&l->freeme)) {
+	if (!list_empty(&nn->fcache_dispose_list)) {
 		LIST_HEAD(dispose);
 		int i;
 
-		spin_lock(&l->lock);
-		for (i = 0; i < 8 && !list_empty(&l->freeme); i++)
-			list_move(l->freeme.next, &dispose);
-		spin_unlock(&l->lock);
-		if (!list_empty(&l->freeme))
+		spin_lock(&nn->fcache_dispose_lock);
+		for (i = 0; i < 8 && !list_empty(&nn->fcache_dispose_list); i++)
+			list_move(nn->fcache_dispose_list.next, &dispose);
+		spin_unlock(&nn->fcache_dispose_lock);
+		if (!list_empty(&nn->fcache_dispose_list))
 			/* Wake up another thread to share the work
 			 * *before* doing any actual disposing.
 			 */

@@ -658,11 +651,11 @@ nfsd_file_queue_for_close(struct inode *inode, struct list_head *dispose)
 }
 
 /**
- * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
+ * nfsd_file_close_inode - attempt a deferred close of a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
  * Close out any open nfsd_files that can be reaped for @inode. The
- * actual freeing is deferred to the dispose_list_delayed infrastructure.
+ * actual freeing is deferred to the nfsd service threads.
  *
  * This is used by the fsnotify callbacks and setlease notifier.
  */

@@ -863,42 +856,14 @@ __nfsd_file_cache_purge(struct net *net)
 	nfsd_file_dispose_list(&dispose);
 }
 
-static struct nfsd_fcache_disposal *
-nfsd_alloc_fcache_disposal(void)
-{
-	struct nfsd_fcache_disposal *l;
-
-	l = kmalloc(sizeof(*l), GFP_KERNEL);
-	if (!l)
-		return NULL;
-	spin_lock_init(&l->lock);
-	INIT_LIST_HEAD(&l->freeme);
-	return l;
-}
-
-static void
-nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
-{
-	nfsd_file_dispose_list(&l->freeme);
-	kfree(l);
-}
-
-static void
-nfsd_free_fcache_disposal_net(struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	nfsd_free_fcache_disposal(l);
-}
-
 int
 nfsd_file_cache_start_net(struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
-	nn->fcache_disposal = nfsd_alloc_fcache_disposal();
-	return nn->fcache_disposal ? 0 : -ENOMEM;
+	spin_lock_init(&nn->fcache_dispose_lock);
+	INIT_LIST_HEAD(&nn->fcache_dispose_list);
+	return 0;
 }
 
 /**

@@ -917,8 +882,10 @@ nfsd_file_cache_purge(struct net *net)
 void
 nfsd_file_cache_shutdown_net(struct net *net)
 {
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
 	nfsd_file_cache_purge(net);
-	nfsd_free_fcache_disposal_net(net);
+	nfsd_file_dispose_list(&nn->fcache_dispose_list);
 }
 
 void

fs/nfsd/netns.h +2 -1

index 09a06e46dab98..610d514d35312 100644
@@ -206,7 +206,8 @@ struct nfsd_net {
 	/* utsname taken from the process that starts the server */
 	char			nfsd_name[UNX_MAXNODENAME+1];
 
-	struct nfsd_fcache_disposal *fcache_disposal;
+	spinlock_t		fcache_dispose_lock;
+	struct list_head	fcache_dispose_list;
 
 	siphash_key_t		siphash_key;

Signature · 1 line

2.53.0

Greg KH

2026-09-17 11:32 UTC #2 lore raw

Re: [PATCH 6.12.y] nfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net

Quoted 201 lines · Sasha Levin

From: Jeff Layton <[email protected]>

[ Upstream commit bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4 ]

Fixes 1463b38e7cf3 ("NFSD: simplify per-net file cache management")

Cc [email protected]

Assisted-by Claude:claude-opus-4-6

Signed-off-by Jeff Layton <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Chuck Lever <[email protected]>

[ adapted disposal-list references while retaining the older unguarded service wake-up flow and removing the legacy kmalloc()-based helper ]

Signed-off-by Sasha Levin <[email protected]>

---
 fs/nfsd/filecache.c | 77 +++++++++++++--------------------------------
 fs/nfsd/netns.h     |  3 +-
 2 files changed, 24 insertions(+), 56 deletions(-)

fs/nfsd/filecache.c +22 ~~-55~~

index 05f0a4867673d..4381d76e83c63 100644
@@ -61,11 +61,6 @@ static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);
 
-struct nfsd_fcache_disposal {
-	spinlock_t lock;
-	struct list_head freeme;
-};
-
 static struct kmem_cache		*nfsd_file_slab;
 static struct kmem_cache		*nfsd_file_mark_slab;
 static struct list_lru			nfsd_file_lru;

@@ -431,25 +426,25 @@ nfsd_file_dispose_list(struct list_head *dispose)
 }
 
 /**
- * nfsd_file_dispose_list_delayed - move list of dead files to net's freeme list
+ * nfsd_file_dispose_list_delayed - queue dead files for nfsd thread disposal
  * @dispose: list of nfsd_files to be disposed
  *
- * Transfers each file to the "freeme" list for its nfsd_net, to eventually
- * be disposed of by the per-net garbage collector.
+ * Transfers each file to the dispose list in its nfsd_net and wakes an nfsd
+ * thread to do the actual close.  This keeps the cost of fput() in the nfsd
+ * threads rather than in the shrinker or GC worker.
  */
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
-	while(!list_empty(dispose)) {
+	while (!list_empty(dispose)) {
 		struct nfsd_file *nf = list_first_entry(dispose,
 						struct nfsd_file, nf_gc);
 		struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
-		struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 		struct svc_serv *serv;
 
-		spin_lock(&l->lock);
-		list_move_tail(&nf->nf_gc, &l->freeme);
-		spin_unlock(&l->lock);
+		spin_lock(&nn->fcache_dispose_lock);
+		list_move_tail(&nf->nf_gc, &nn->fcache_dispose_list);
+		spin_unlock(&nn->fcache_dispose_lock);
 
 		/*
 		 * The filecache laundrette is shut down after the

@@ -473,17 +468,15 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose)
  */
 void nfsd_file_net_dispose(struct nfsd_net *nn)
 {
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	if (!list_empty(&l->freeme)) {
+	if (!list_empty(&nn->fcache_dispose_list)) {
 		LIST_HEAD(dispose);
 		int i;
 
-		spin_lock(&l->lock);
-		for (i = 0; i < 8 && !list_empty(&l->freeme); i++)
-			list_move(l->freeme.next, &dispose);
-		spin_unlock(&l->lock);
-		if (!list_empty(&l->freeme))
+		spin_lock(&nn->fcache_dispose_lock);
+		for (i = 0; i < 8 && !list_empty(&nn->fcache_dispose_list); i++)
+			list_move(nn->fcache_dispose_list.next, &dispose);
+		spin_unlock(&nn->fcache_dispose_lock);
+		if (!list_empty(&nn->fcache_dispose_list))
 			/* Wake up another thread to share the work
 			 * *before* doing any actual disposing.
 			 */

@@ -658,11 +651,11 @@ nfsd_file_queue_for_close(struct inode *inode, struct list_head *dispose)
 }
 
 /**
- * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
+ * nfsd_file_close_inode - attempt a deferred close of a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
  * Close out any open nfsd_files that can be reaped for @inode. The
- * actual freeing is deferred to the dispose_list_delayed infrastructure.
+ * actual freeing is deferred to the nfsd service threads.
  *
  * This is used by the fsnotify callbacks and setlease notifier.
  */

@@ -863,42 +856,14 @@ __nfsd_file_cache_purge(struct net *net)
 	nfsd_file_dispose_list(&dispose);
 }
 
-static struct nfsd_fcache_disposal *
-nfsd_alloc_fcache_disposal(void)
-{
-	struct nfsd_fcache_disposal *l;
-
-	l = kmalloc(sizeof(*l), GFP_KERNEL);
-	if (!l)
-		return NULL;
-	spin_lock_init(&l->lock);
-	INIT_LIST_HEAD(&l->freeme);
-	return l;
-}
-
-static void
-nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
-{
-	nfsd_file_dispose_list(&l->freeme);
-	kfree(l);
-}
-
-static void
-nfsd_free_fcache_disposal_net(struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	nfsd_free_fcache_disposal(l);
-}
-
 int
 nfsd_file_cache_start_net(struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
-	nn->fcache_disposal = nfsd_alloc_fcache_disposal();
-	return nn->fcache_disposal ? 0 : -ENOMEM;
+	spin_lock_init(&nn->fcache_dispose_lock);
+	INIT_LIST_HEAD(&nn->fcache_dispose_list);
+	return 0;
 }
 
 /**

@@ -917,8 +882,10 @@ nfsd_file_cache_purge(struct net *net)
 void
 nfsd_file_cache_shutdown_net(struct net *net)
 {
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
 	nfsd_file_cache_purge(net);
-	nfsd_free_fcache_disposal_net(net);
+	nfsd_file_dispose_list(&nn->fcache_dispose_list);
 }
 
 void

fs/nfsd/netns.h +2 -1

index 09a06e46dab98..610d514d35312 100644
@@ -206,7 +206,8 @@ struct nfsd_net {
 	/* utsname taken from the process that starts the server */
 	char			nfsd_name[UNX_MAXNODENAME+1];
 
-	struct nfsd_fcache_disposal *fcache_disposal;
+	spinlock_t		fcache_dispose_lock;
+	struct list_head	fcache_dispose_list;
 
 	siphash_key_t		siphash_key;

Signature · 1 line

2.53.0

Does not apply