FAILED: patch "[PATCH] xfs: check for dead buffers in xfs_buf_find_insert" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 07eae0fa67ca4bbb199ad85645e0f9dfaef931cd
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025020447-stinking-untying-4604@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 07eae0fa67ca4bbb199ad85645e0f9dfaef931cd Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Thu, 16 Jan 2025 07:01:41 +0100
Subject: [PATCH] xfs: check for dead buffers in xfs_buf_find_insert

Commit 32dd4f9c506b ("xfs: remove a superflous hash lookup when inserting
new buffers") converted xfs_buf_find_insert to use
rhashtable_lookup_get_insert_fast and thus an operation that returns the
existing buffer when an insert would duplicate the hash key.  But this
code path misses the check for a buffer with a reference count of zero,
which could lead to reusing an about to be freed buffer.  Fix this by
using the same atomic_inc_not_zero pattern as xfs_buf_insert.

Fixes: 32dd4f9c506b ("xfs: remove a superflous hash lookup when inserting new buffers")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: stable@vger.kernel.org # v6.0
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index d9636bff16ce..183428fbc607 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -655,9 +655,8 @@ xfs_buf_find_insert(
 		spin_unlock(&bch->bc_lock);
 		goto out_free_buf;
 	}
-	if (bp) {
+	if (bp && atomic_inc_not_zero(&bp->b_hold)) {
 		/* found an existing buffer */
-		atomic_inc(&bp->b_hold);
 		spin_unlock(&bch->bc_lock);
 		error = xfs_buf_find_lock(bp, flags);
 		if (error)