FAILED: patch "[PATCH] mtd: mtdsuper: Fix MTD device reference leak in mtd_get_sb()" failed to apply to 5.10-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 62ee3da38f41bef83c1cf250f6816a0ee187674b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107061708-failed-5.10-62ee3da38f41@kernel.org' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Thanks,
Sasha

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

From 62ee3da38f41bef83c1cf250f6816a0ee187674b Mon Sep 17 00:00:00 2001
From: Wentao Liang <vulab@iscas.ac.cn>
Date: Thu, 17 Sep 2026 10:25:50 +0000
Subject: [PATCH] mtd: mtdsuper: Fix MTD device reference leak in mtd_get_sb()

mtd_get_sb() is called with a reference to the MTD device already
taken by the caller.  When sget_dev() fails, the function returns the
error without dropping that reference, so the device is never released
and its refcount never reaches zero.  Every mount attempt on an MTD
device whose superblock cannot be set up leaks a reference.

Restore the put_mtd_device() that the fs_context conversion dropped on
this path.

Fixes: 0f071004109d ("mtd: Provide fs_context-aware mount_mtd() replacement")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 drivers/mtd/mtdsuper.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c
index c709ff7aa6b57..02eede3fe582e 100644
--- a/drivers/mtd/mtdsuper.c
+++ b/drivers/mtd/mtdsuper.c
@@ -31,8 +31,10 @@ static int mtd_get_sb(struct fs_context *fc,
 	int ret;
 
 	sb = sget_dev(fc, MKDEV(MTD_BLOCK_MAJOR, mtd->index));
-	if (IS_ERR(sb))
+	if (IS_ERR(sb)) {
+		put_mtd_device(mtd);
 		return PTR_ERR(sb);
+	}
 
 	if (sb->s_root) {
 		/* new mountpoint for an already mounted superblock */
-- 
2.53.0