FAILED: patch "[PATCH] fsnotify: Fix stale object mask after concurrent mark updates" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] fsnotify: Fix stale object mask after concurrent mark updates" failed to apply to 6.18-stable tree

[gregkh]

The patch below does not apply to the 6.18-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 <stable@vger.kernel.org>.

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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x e422777fdd4746de1109575c51e65038d4c5c1be
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090335-leotard-duffel-dd93@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From e422777fdd4746de1109575c51e65038d4c5c1be Mon Sep 17 00:00:00 2001
From: Youngjae Kwon <yjkwon0026@snu.ac.kr>
Date: Sun, 2 Aug 2026 10:58:00 +0900
Subject: [PATCH] fsnotify: Fix stale object mask after concurrent mark updates

When a mark gets a new event bit, fanotify and inotify may avoid
recalculating the object mask if the cached aggregate already contains that
bit. This is racy with a recalculation triggered by a concurrent update to
another mark on the same connector.

The concurrent scan can read the mark before the new bit is added, while
the updater reads the old aggregate before that scan publishes its result.
The updater then skips recalculation and the scan publishes a mask without
the bit, leaving the object mask stale after both updates complete.

This can be reproduced with two fanotify groups watching the same inode:
one thread removes FAN_MODIFY from one existing mark while another thread
adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return,
writes can fail to produce FAN_MODIFY for the group whose mark now contains
the bit. This was reproduced on an unmodified v6.12.95 kernel. The
equivalent inotify interleaving loses IN_MODIFY events.

For normal fanotify additions, recalculate whenever the raw mark mask
changes. The normal mask is not cleared asynchronously, so an unchanged
addition cannot introduce missing interest. Always recalculate ignore-mask
updates because FS_MODIFY handling may clear the ignore mask without taking
mark->lock, making snapshot comparisons unreliable.

Always recalculate after updating an existing inotify watch. Its replace
path temporarily sets mark->mask to zero, so a concurrent scan can observe
zero even when the old and final masks are equal. Assigning the replacement
mask directly would avoid the transient zero, but existing-watch updates
are infrequent, so unconditional recalculation is simpler.

Link: https://lore.kernel.org/all/CACwKKmCZdiZDoFuYm6LZhQ=XvHPk0fNKH=X3LmoXMqakYqJaNw@mail.gmail.com/
Fixes: 63c882a05416 ("inotify: reimplement inotify using fsnotify")
Fixes: 912ee3946c5e ("fanotify: do not call fanotify_update_object_mask in fanotify_add_mark")
Cc: stable@vger.kernel.org # needs adjustments for <= 7.0
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
Link: https://patch.msgid.link/20260802015801.2426818-1-yjkwon0026@snu.ac.kr
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 463495a78693..a32c6634d592 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1321,16 +1321,18 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
 static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 				      __u32 mask, unsigned int fan_flags)
 {
+	__u32 old_mask;
 	bool recalc;
 
 	spin_lock(&fsn_mark->lock);
-	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
+	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS)) {
+		old_mask = fsn_mark->mask;
 		fsn_mark->mask |= mask;
-	else
+		recalc = old_mask != fsn_mark->mask;
+	} else {
 		fsn_mark->ignore_mask |= mask;
-
-	recalc = fsnotify_calc_mask(fsn_mark) &
-		~fsnotify_conn_mask(fsn_mark->connector);
+		recalc = true;
+	}
 
 	recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
 	spin_unlock(&fsn_mark->lock);
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index ed37491c1618..5f19c24ec187 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -539,7 +539,6 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
 {
 	struct fsnotify_mark *fsn_mark;
 	struct inotify_inode_mark *i_mark;
-	__u32 old_mask, new_mask;
 	int replace = !(arg & IN_MASK_ADD);
 	int create = (arg & IN_MASK_CREATE);
 	int ret;
@@ -555,27 +554,15 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
 	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 
 	spin_lock(&fsn_mark->lock);
-	old_mask = fsn_mark->mask;
 	if (replace) {
 		fsn_mark->mask = 0;
 		fsn_mark->flags &= ~INOTIFY_MARK_FLAGS;
 	}
 	fsn_mark->mask |= inotify_arg_to_mask(inode, arg);
 	fsn_mark->flags |= inotify_arg_to_flags(arg);
-	new_mask = fsn_mark->mask;
 	spin_unlock(&fsn_mark->lock);
 
-	if (old_mask != new_mask) {
-		/* more bits in old than in new? */
-		int dropped = (old_mask & ~new_mask);
-		/* more bits in this fsn_mark than the inode's mask? */
-		int do_inode = (new_mask & ~READ_ONCE(inode->i_fsnotify_mask));
-
-		/* update the inode with this new fsn_mark */
-		if (dropped || do_inode)
-			fsnotify_recalc_mask(fsn_mark->connector);
-
-	}
+	fsnotify_recalc_mask(fsn_mark->connector);
 
 	/* return the wd */
 	ret = i_mark->wd;

[PATCH 6.18.y] fsnotify: Fix stale object mask after concurrent mark updates

[Youngjae Kwon]

[ Upstream commit e422777fdd4746de1109575c51e65038d4c5c1be ]

When a mark gets a new event bit, fanotify and inotify may avoid
recalculating the object mask if the cached aggregate already contains that
bit. This is racy with a recalculation triggered by a concurrent update to
another mark on the same connector.

The concurrent scan can read the mark before the new bit is added, while
the updater reads the old aggregate before that scan publishes its result.
The updater then skips recalculation and the scan publishes a mask without
the bit, leaving the object mask stale after both updates complete.

This can be reproduced with two fanotify groups watching the same inode:
one thread removes FAN_MODIFY from one existing mark while another thread
adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return,
writes can fail to produce FAN_MODIFY for the group whose mark now contains
the bit. This was reproduced on an unmodified v6.12.95 kernel. The
equivalent inotify interleaving loses IN_MODIFY events.

For normal fanotify additions, recalculate whenever the raw mark mask
changes. The normal mask is not cleared asynchronously, so an unchanged
addition cannot introduce missing interest. Always recalculate ignore-mask
updates because FS_MODIFY handling may clear the ignore mask without taking
mark->lock, making snapshot comparisons unreliable.

Always recalculate after updating an existing inotify watch. Its replace
path temporarily sets mark->mask to zero, so a concurrent scan can observe
zero even when the old and final masks are equal. Assigning the replacement
mask directly would avoid the transient zero, but existing-watch updates
are infrequent, so unconditional recalculation is simpler.

Link: https://lore.kernel.org/all/CACwKKmCZdiZDoFuYm6LZhQ=XvHPk0fNKH=X3LmoXMqakYqJaNw@mail.gmail.com/
Fixes: 63c882a05416 ("inotify: reimplement inotify using fsnotify")
Fixes: 912ee3946c5e ("fanotify: do not call fanotify_update_object_mask in fanotify_add_mark")
Cc: stable@vger.kernel.org # needs adjustments for <= 7.0
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
Link: https://patch.msgid.link/20260802015801.2426818-1-yjkwon0026@snu.ac.kr
Signed-off-by: Jan Kara <jack@suse.cz>
(cherry picked from commit e422777fdd4746de1109575c51e65038d4c5c1be)
[yjkwon0026: Resolve the inotify conflict by retaining the branch-native
inode->i_fsnotify_marks argument to fsnotify_recalc_mask(). This tree
lacks 4520b96b8136 ("fsnotify: inotify: pass mark connector to
fsnotify_recalc_mask()"). The surrounding conditional is deleted by
this patch, so that commit is not a prerequisite for this fix.]
Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
---
 fs/notify/fanotify/fanotify_user.c | 12 +++++++-----
 fs/notify/inotify/inotify_user.c   | 15 +--------------
 2 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 5c30f4d8c7c1..e0a0f67b1350 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1327,16 +1327,18 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
 static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 				      __u32 mask, unsigned int fan_flags)
 {
+	__u32 old_mask;
 	bool recalc;
 
 	spin_lock(&fsn_mark->lock);
-	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
+	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS)) {
+		old_mask = fsn_mark->mask;
 		fsn_mark->mask |= mask;
-	else
+		recalc = old_mask != fsn_mark->mask;
+	} else {
 		fsn_mark->ignore_mask |= mask;
-
-	recalc = fsnotify_calc_mask(fsn_mark) &
-		~fsnotify_conn_mask(fsn_mark->connector);
+		recalc = true;
+	}
 
 	recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
 	spin_unlock(&fsn_mark->lock);
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 0d813c52ff9c..2a8a83d8f4a7 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -539,7 +539,6 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
 {
 	struct fsnotify_mark *fsn_mark;
 	struct inotify_inode_mark *i_mark;
-	__u32 old_mask, new_mask;
 	int replace = !(arg & IN_MASK_ADD);
 	int create = (arg & IN_MASK_CREATE);
 	int ret;
@@ -555,27 +554,15 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
 	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 
 	spin_lock(&fsn_mark->lock);
-	old_mask = fsn_mark->mask;
 	if (replace) {
 		fsn_mark->mask = 0;
 		fsn_mark->flags &= ~INOTIFY_MARK_FLAGS;
 	}
 	fsn_mark->mask |= inotify_arg_to_mask(inode, arg);
 	fsn_mark->flags |= inotify_arg_to_flags(arg);
-	new_mask = fsn_mark->mask;
 	spin_unlock(&fsn_mark->lock);
 
-	if (old_mask != new_mask) {
-		/* more bits in old than in new? */
-		int dropped = (old_mask & ~new_mask);
-		/* more bits in this fsn_mark than the inode's mask? */
-		int do_inode = (new_mask & ~READ_ONCE(inode->i_fsnotify_mask));
-
-		/* update the inode with this new fsn_mark */
-		if (dropped || do_inode)
-			fsnotify_recalc_mask(inode->i_fsnotify_marks);
-
-	}
+	fsnotify_recalc_mask(inode->i_fsnotify_marks);
 
 	/* return the wd */
 	ret = i_mark->wd;
-- 
2.50.1

Re: [PATCH 6.18.y] fsnotify: Fix stale object mask after concurrent mark updates

[Amir Goldstein]

On Sat, Sep 5, 2026 at 4:48 AM Youngjae Kwon <yjkwon0026@snu.ac.kr> wrote:
>
> [ Upstream commit e422777fdd4746de1109575c51e65038d4c5c1be ]
>
> When a mark gets a new event bit, fanotify and inotify may avoid
> recalculating the object mask if the cached aggregate already contains that
> bit. This is racy with a recalculation triggered by a concurrent update to
> another mark on the same connector.
>
> The concurrent scan can read the mark before the new bit is added, while
> the updater reads the old aggregate before that scan publishes its result.
> The updater then skips recalculation and the scan publishes a mask without
> the bit, leaving the object mask stale after both updates complete.
>
> This can be reproduced with two fanotify groups watching the same inode:
> one thread removes FAN_MODIFY from one existing mark while another thread
> adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return,
> writes can fail to produce FAN_MODIFY for the group whose mark now contains
> the bit. This was reproduced on an unmodified v6.12.95 kernel. The
> equivalent inotify interleaving loses IN_MODIFY events.
>
> For normal fanotify additions, recalculate whenever the raw mark mask
> changes. The normal mask is not cleared asynchronously, so an unchanged
> addition cannot introduce missing interest. Always recalculate ignore-mask
> updates because FS_MODIFY handling may clear the ignore mask without taking
> mark->lock, making snapshot comparisons unreliable.
>
> Always recalculate after updating an existing inotify watch. Its replace
> path temporarily sets mark->mask to zero, so a concurrent scan can observe
> zero even when the old and final masks are equal. Assigning the replacement
> mask directly would avoid the transient zero, but existing-watch updates
> are infrequent, so unconditional recalculation is simpler.
>
> Link: https://lore.kernel.org/all/CACwKKmCZdiZDoFuYm6LZhQ=XvHPk0fNKH=X3LmoXMqakYqJaNw@mail.gmail.com/
> Fixes: 63c882a05416 ("inotify: reimplement inotify using fsnotify")
> Fixes: 912ee3946c5e ("fanotify: do not call fanotify_update_object_mask in fanotify_add_mark")
> Cc: stable@vger.kernel.org # needs adjustments for <= 7.0
> Suggested-by: Jan Kara <jack@suse.cz>
> Suggested-by: Amir Goldstein <amir73il@gmail.com>
> Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
> Link: https://patch.msgid.link/20260802015801.2426818-1-yjkwon0026@snu.ac.kr
> Signed-off-by: Jan Kara <jack@suse.cz>
> (cherry picked from commit e422777fdd4746de1109575c51e65038d4c5c1be)
> [yjkwon0026: Resolve the inotify conflict by retaining the branch-native
> inode->i_fsnotify_marks argument to fsnotify_recalc_mask(). This tree
> lacks 4520b96b8136 ("fsnotify: inotify: pass mark connector to
> fsnotify_recalc_mask()"). The surrounding conditional is deleted by
> this patch, so that commit is not a prerequisite for this fix.]

I slightly lean towards backporting the trivial sparse fix to
keep the histories of master and stable in-sync with cleanly applied commits
without the need for this explanation, but I do not insist.

Thanks,
Amir.

> Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
> ---
>  fs/notify/fanotify/fanotify_user.c | 12 +++++++-----
>  fs/notify/inotify/inotify_user.c   | 15 +--------------
>  2 files changed, 8 insertions(+), 19 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 5c30f4d8c7c1..e0a0f67b1350 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -1327,16 +1327,18 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
>  static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
>                                       __u32 mask, unsigned int fan_flags)
>  {
> +       __u32 old_mask;
>         bool recalc;
>
>         spin_lock(&fsn_mark->lock);
> -       if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
> +       if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS)) {
> +               old_mask = fsn_mark->mask;
>                 fsn_mark->mask |= mask;
> -       else
> +               recalc = old_mask != fsn_mark->mask;
> +       } else {
>                 fsn_mark->ignore_mask |= mask;
> -
> -       recalc = fsnotify_calc_mask(fsn_mark) &
> -               ~fsnotify_conn_mask(fsn_mark->connector);
> +               recalc = true;
> +       }
>
>         recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
>         spin_unlock(&fsn_mark->lock);
> diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
> index 0d813c52ff9c..2a8a83d8f4a7 100644
> --- a/fs/notify/inotify/inotify_user.c
> +++ b/fs/notify/inotify/inotify_user.c
> @@ -539,7 +539,6 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
>  {
>         struct fsnotify_mark *fsn_mark;
>         struct inotify_inode_mark *i_mark;
> -       __u32 old_mask, new_mask;
>         int replace = !(arg & IN_MASK_ADD);
>         int create = (arg & IN_MASK_CREATE);
>         int ret;
> @@ -555,27 +554,15 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
>         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
>
>         spin_lock(&fsn_mark->lock);
> -       old_mask = fsn_mark->mask;
>         if (replace) {
>                 fsn_mark->mask = 0;
>                 fsn_mark->flags &= ~INOTIFY_MARK_FLAGS;
>         }
>         fsn_mark->mask |= inotify_arg_to_mask(inode, arg);
>         fsn_mark->flags |= inotify_arg_to_flags(arg);
> -       new_mask = fsn_mark->mask;
>         spin_unlock(&fsn_mark->lock);
>
> -       if (old_mask != new_mask) {
> -               /* more bits in old than in new? */
> -               int dropped = (old_mask & ~new_mask);
> -               /* more bits in this fsn_mark than the inode's mask? */
> -               int do_inode = (new_mask & ~READ_ONCE(inode->i_fsnotify_mask));
> -
> -               /* update the inode with this new fsn_mark */
> -               if (dropped || do_inode)
> -                       fsnotify_recalc_mask(inode->i_fsnotify_marks);
> -
> -       }
> +       fsnotify_recalc_mask(inode->i_fsnotify_marks);
>
>         /* return the wd */
>         ret = i_mark->wd;
> --
> 2.50.1
>

[PATCH 6.18.y v2 1/2] fsnotify: inotify: pass mark connector to fsnotify_recalc_mask()

[Youngjae Kwon]

From: Sun Jian <sun.jian.kdev@gmail.com>

[ Upstream commit 4520b96b8136ba2465a3f4dc5c3fb8bdf3d92e4e ]

fsnotify_recalc_mask() expects a plain struct fsnotify_mark_connector *,
but inode->i_fsnotify_marks is an __rcu pointer.  Use fsn_mark->connector
instead to avoid sparse "different address spaces" warnings.

Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
Link: https://patch.msgid.link/20260214051217.1381363-1-sun.jian.kdev@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
(cherry picked from commit 4520b96b8136ba2465a3f4dc5c3fb8bdf3d92e4e)
Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
---
 fs/notify/inotify/inotify_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 0d813c52ff9c..905c27e9cd38 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -573,7 +573,7 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
 
 		/* update the inode with this new fsn_mark */
 		if (dropped || do_inode)
-			fsnotify_recalc_mask(inode->i_fsnotify_marks);
+			fsnotify_recalc_mask(fsn_mark->connector);
 
 	}
 
-- 
2.50.1

[PATCH 6.18.y v2 2/2] fsnotify: Fix stale object mask after concurrent mark updates

[Youngjae Kwon]

[ Upstream commit e422777fdd4746de1109575c51e65038d4c5c1be ]

When a mark gets a new event bit, fanotify and inotify may avoid
recalculating the object mask if the cached aggregate already contains that
bit. This is racy with a recalculation triggered by a concurrent update to
another mark on the same connector.

The concurrent scan can read the mark before the new bit is added, while
the updater reads the old aggregate before that scan publishes its result.
The updater then skips recalculation and the scan publishes a mask without
the bit, leaving the object mask stale after both updates complete.

This can be reproduced with two fanotify groups watching the same inode:
one thread removes FAN_MODIFY from one existing mark while another thread
adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return,
writes can fail to produce FAN_MODIFY for the group whose mark now contains
the bit. This was reproduced on an unmodified v6.12.95 kernel. The
equivalent inotify interleaving loses IN_MODIFY events.

For normal fanotify additions, recalculate whenever the raw mark mask
changes. The normal mask is not cleared asynchronously, so an unchanged
addition cannot introduce missing interest. Always recalculate ignore-mask
updates because FS_MODIFY handling may clear the ignore mask without taking
mark->lock, making snapshot comparisons unreliable.

Always recalculate after updating an existing inotify watch. Its replace
path temporarily sets mark->mask to zero, so a concurrent scan can observe
zero even when the old and final masks are equal. Assigning the replacement
mask directly would avoid the transient zero, but existing-watch updates
are infrequent, so unconditional recalculation is simpler.

Link: https://lore.kernel.org/all/CACwKKmCZdiZDoFuYm6LZhQ=XvHPk0fNKH=X3LmoXMqakYqJaNw@mail.gmail.com/
Fixes: 63c882a05416 ("inotify: reimplement inotify using fsnotify")
Fixes: 912ee3946c5e ("fanotify: do not call fanotify_update_object_mask in fanotify_add_mark")
Cc: stable@vger.kernel.org # needs adjustments for <= 7.0
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
Link: https://patch.msgid.link/20260802015801.2426818-1-yjkwon0026@snu.ac.kr
Signed-off-by: Jan Kara <jack@suse.cz>
(cherry picked from commit e422777fdd4746de1109575c51e65038d4c5c1be)
Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
---
 fs/notify/fanotify/fanotify_user.c | 12 +++++++-----
 fs/notify/inotify/inotify_user.c   | 15 +--------------
 2 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 5c30f4d8c7c1..e0a0f67b1350 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1327,16 +1327,18 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
 static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 				      __u32 mask, unsigned int fan_flags)
 {
+	__u32 old_mask;
 	bool recalc;
 
 	spin_lock(&fsn_mark->lock);
-	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
+	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS)) {
+		old_mask = fsn_mark->mask;
 		fsn_mark->mask |= mask;
-	else
+		recalc = old_mask != fsn_mark->mask;
+	} else {
 		fsn_mark->ignore_mask |= mask;
-
-	recalc = fsnotify_calc_mask(fsn_mark) &
-		~fsnotify_conn_mask(fsn_mark->connector);
+		recalc = true;
+	}
 
 	recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
 	spin_unlock(&fsn_mark->lock);
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 905c27e9cd38..6eaf0d382eec 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -539,7 +539,6 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
 {
 	struct fsnotify_mark *fsn_mark;
 	struct inotify_inode_mark *i_mark;
-	__u32 old_mask, new_mask;
 	int replace = !(arg & IN_MASK_ADD);
 	int create = (arg & IN_MASK_CREATE);
 	int ret;
@@ -555,27 +554,15 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
 	i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 
 	spin_lock(&fsn_mark->lock);
-	old_mask = fsn_mark->mask;
 	if (replace) {
 		fsn_mark->mask = 0;
 		fsn_mark->flags &= ~INOTIFY_MARK_FLAGS;
 	}
 	fsn_mark->mask |= inotify_arg_to_mask(inode, arg);
 	fsn_mark->flags |= inotify_arg_to_flags(arg);
-	new_mask = fsn_mark->mask;
 	spin_unlock(&fsn_mark->lock);
 
-	if (old_mask != new_mask) {
-		/* more bits in old than in new? */
-		int dropped = (old_mask & ~new_mask);
-		/* more bits in this fsn_mark than the inode's mask? */
-		int do_inode = (new_mask & ~READ_ONCE(inode->i_fsnotify_mask));
-
-		/* update the inode with this new fsn_mark */
-		if (dropped || do_inode)
-			fsnotify_recalc_mask(fsn_mark->connector);
-
-	}
+	fsnotify_recalc_mask(fsn_mark->connector);
 
 	/* return the wd */
 	ret = i_mark->wd;
-- 
2.50.1

Re: [PATCH 6.18.y v2 1/2] fsnotify: inotify: pass mark connector to fsnotify_recalc_mask()

[Amir Goldstein]

On Sun, Sep 6, 2026 at 5:09 AM Youngjae Kwon <yjkwon0026@snu.ac.kr> wrote:
>
> From: Sun Jian <sun.jian.kdev@gmail.com>
>
> [ Upstream commit 4520b96b8136ba2465a3f4dc5c3fb8bdf3d92e4e ]
>
> fsnotify_recalc_mask() expects a plain struct fsnotify_mark_connector *,
> but inode->i_fsnotify_marks is an __rcu pointer.  Use fsn_mark->connector
> instead to avoid sparse "different address spaces" warnings.
>
> Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
> Link: https://patch.msgid.link/20260214051217.1381363-1-sun.jian.kdev@gmail.com
> Signed-off-by: Jan Kara <jack@suse.cz>
> (cherry picked from commit 4520b96b8136ba2465a3f4dc5c3fb8bdf3d92e4e)

This line is redundant

otherwise

Acked-by: Amir Goldstein <amir73il@gmail.com>

> Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
> ---
>  fs/notify/inotify/inotify_user.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
> index 0d813c52ff9c..905c27e9cd38 100644
> --- a/fs/notify/inotify/inotify_user.c
> +++ b/fs/notify/inotify/inotify_user.c
> @@ -573,7 +573,7 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
>
>                 /* update the inode with this new fsn_mark */
>                 if (dropped || do_inode)
> -                       fsnotify_recalc_mask(inode->i_fsnotify_marks);
> +                       fsnotify_recalc_mask(fsn_mark->connector);
>
>         }
>
> --
> 2.50.1
>

Re: [PATCH 6.18.y v2 2/2] fsnotify: Fix stale object mask after concurrent mark updates

[Amir Goldstein]

On Sun, Sep 6, 2026 at 5:09 AM Youngjae Kwon <yjkwon0026@snu.ac.kr> wrote:
>
> [ Upstream commit e422777fdd4746de1109575c51e65038d4c5c1be ]
>
> When a mark gets a new event bit, fanotify and inotify may avoid
> recalculating the object mask if the cached aggregate already contains that
> bit. This is racy with a recalculation triggered by a concurrent update to
> another mark on the same connector.
>
> The concurrent scan can read the mark before the new bit is added, while
> the updater reads the old aggregate before that scan publishes its result.
> The updater then skips recalculation and the scan publishes a mask without
> the bit, leaving the object mask stale after both updates complete.
>
> This can be reproduced with two fanotify groups watching the same inode:
> one thread removes FAN_MODIFY from one existing mark while another thread
> adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return,
> writes can fail to produce FAN_MODIFY for the group whose mark now contains
> the bit. This was reproduced on an unmodified v6.12.95 kernel. The
> equivalent inotify interleaving loses IN_MODIFY events.
>
> For normal fanotify additions, recalculate whenever the raw mark mask
> changes. The normal mask is not cleared asynchronously, so an unchanged
> addition cannot introduce missing interest. Always recalculate ignore-mask
> updates because FS_MODIFY handling may clear the ignore mask without taking
> mark->lock, making snapshot comparisons unreliable.
>
> Always recalculate after updating an existing inotify watch. Its replace
> path temporarily sets mark->mask to zero, so a concurrent scan can observe
> zero even when the old and final masks are equal. Assigning the replacement
> mask directly would avoid the transient zero, but existing-watch updates
> are infrequent, so unconditional recalculation is simpler.
>
> Link: https://lore.kernel.org/all/CACwKKmCZdiZDoFuYm6LZhQ=XvHPk0fNKH=X3LmoXMqakYqJaNw@mail.gmail.com/
> Fixes: 63c882a05416 ("inotify: reimplement inotify using fsnotify")
> Fixes: 912ee3946c5e ("fanotify: do not call fanotify_update_object_mask in fanotify_add_mark")
> Cc: stable@vger.kernel.org # needs adjustments for <= 7.0
> Suggested-by: Jan Kara <jack@suse.cz>
> Suggested-by: Amir Goldstein <amir73il@gmail.com>
> Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
> Link: https://patch.msgid.link/20260802015801.2426818-1-yjkwon0026@snu.ac.kr
> Signed-off-by: Jan Kara <jack@suse.cz>
> (cherry picked from commit e422777fdd4746de1109575c51e65038d4c5c1be)

This line is redundant

otherwise

Acked-by: Amir Goldstein <amir73il@gmail.com>

> Signed-off-by: Youngjae Kwon <yjkwon0026@snu.ac.kr>
> ---
>  fs/notify/fanotify/fanotify_user.c | 12 +++++++-----
>  fs/notify/inotify/inotify_user.c   | 15 +--------------
>  2 files changed, 8 insertions(+), 19 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 5c30f4d8c7c1..e0a0f67b1350 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -1327,16 +1327,18 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
>  static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
>                                       __u32 mask, unsigned int fan_flags)
>  {
> +       __u32 old_mask;
>         bool recalc;
>
>         spin_lock(&fsn_mark->lock);
> -       if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
> +       if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS)) {
> +               old_mask = fsn_mark->mask;
>                 fsn_mark->mask |= mask;
> -       else
> +               recalc = old_mask != fsn_mark->mask;
> +       } else {
>                 fsn_mark->ignore_mask |= mask;
> -
> -       recalc = fsnotify_calc_mask(fsn_mark) &
> -               ~fsnotify_conn_mask(fsn_mark->connector);
> +               recalc = true;
> +       }
>
>         recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
>         spin_unlock(&fsn_mark->lock);
> diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
> index 905c27e9cd38..6eaf0d382eec 100644
> --- a/fs/notify/inotify/inotify_user.c
> +++ b/fs/notify/inotify/inotify_user.c
> @@ -539,7 +539,6 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
>  {
>         struct fsnotify_mark *fsn_mark;
>         struct inotify_inode_mark *i_mark;
> -       __u32 old_mask, new_mask;
>         int replace = !(arg & IN_MASK_ADD);
>         int create = (arg & IN_MASK_CREATE);
>         int ret;
> @@ -555,27 +554,15 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,
>         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
>
>         spin_lock(&fsn_mark->lock);
> -       old_mask = fsn_mark->mask;
>         if (replace) {
>                 fsn_mark->mask = 0;
>                 fsn_mark->flags &= ~INOTIFY_MARK_FLAGS;
>         }
>         fsn_mark->mask |= inotify_arg_to_mask(inode, arg);
>         fsn_mark->flags |= inotify_arg_to_flags(arg);
> -       new_mask = fsn_mark->mask;
>         spin_unlock(&fsn_mark->lock);
>
> -       if (old_mask != new_mask) {
> -               /* more bits in old than in new? */
> -               int dropped = (old_mask & ~new_mask);
> -               /* more bits in this fsn_mark than the inode's mask? */
> -               int do_inode = (new_mask & ~READ_ONCE(inode->i_fsnotify_mask));
> -
> -               /* update the inode with this new fsn_mark */
> -               if (dropped || do_inode)
> -                       fsnotify_recalc_mask(fsn_mark->connector);
> -
> -       }
> +       fsnotify_recalc_mask(fsn_mark->connector);
>
>         /* return the wd */
>         ret = i_mark->wd;
> --
> 2.50.1
>

Re: [PATCH 6.18.y] fsnotify: Fix stale object mask after concurrent mark updates

[Sasha Levin]

> When a mark gets a new event bit, fanotify and inotify may avoid
> recalculating the object mask if the cached aggregate already contains that
> bit. This is racy with a recalculation triggered by a concurrent update to
> another mark on the same connector.
>
> The concurrent scan can read the mark before the new bit is added, while

Queued for 6.18, thanks.

-- 
Thanks,
Sasha

Re: [PATCH 6.18.y v2 1/2] fsnotify: inotify: pass mark connector to fsnotify_recalc_mask()

[Sasha Levin]

> [ Upstream commit 4520b96b8136ba2465a3f4dc5c3fb8bdf3d92e4e ]
>
> fsnotify_recalc_mask() expects a plain struct fsnotify_mark_connector *,
> but inode->i_fsnotify_marks is an __rcu pointer.  Use fsn_mark->connector
> instead to avoid sparse "different address spaces" warnings.

Queued for 6.18, thanks.

-- 
Thanks,
Sasha