linux-kernel - [PATCH 5.10/5.15] jfs: add check if log->bdev is NULL in lbmStartIO()

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Message-Id: <20240112165007.4764-1-mish.uxin2012@yandex.ru>
Date: Fri, 12 Jan 2024 19:50:07 +0300
From: Mikhail Ukhin <mish.uxin2012@...dex.ru>
To: Dave Kleikamp <shaggy@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
	Jens Axboe <axboe@...nel.dk>,
	Jan Kara <jack@...e.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Mikhail Ukhin <mish.uxin2012@...dex.ru>,
	jfs-discussion@...ts.sourceforge.net,
	stable@...r.kernel.org,
	lvc-project@...uxtesting.org,
	linux-kernel@...r.kernel.org,
	Mikhail Ivanov <iwanov-23@...ru>,
	Pavel Koshutin <koshutin.pavel@...dex.ru>,
	Artem Sadovnikov <ancowi69@...il.com>
Subject: [PATCH 5.10/5.15] jfs: add check if log->bdev is NULL in lbmStartIO()

Fuzzing of 5.10 stable branch shows NULL pointer dereference happens in 
lbmStartIO() on log->bdev pointer. The reason for bdev being NULL is the 
JFS_NOINTEGRITY flag is set on mount of this fs. When this flag is enabled,
it results in the open_dummy_log function being called, which initializes a
new dummy_log, but does not assign a value to bdev.

The error is fixed in 5.18 by commit
07888c665b405b1cd3577ddebfeb74f4717a84c4.
Backport of this commit is too intrusive, so it is more reasonable to apply
a small patch to fix this issue.

Found by Linux Verification Center (linuxtesting.org) with syzkaller.

Signed-off-by: Mikhail Ukhin <mish.uxin2012@...dex.ru>
Signed-off-by: Mikhail Ivanov <iwanov-23@...ru>
Signed-off-by: Pavel Koshutin <koshutin.pavel@...dex.ru>
Signed-off-by: Artem Sadovnikov <ancowi69@...il.com>
---
 fs/jfs/jfs_logmgr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 78fd136ac13b..d6f0fea96ba1 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1983,7 +1983,8 @@ static int lbmRead(struct jfs_log * log, int pn, struct lbuf ** bpp)
 	bio = bio_alloc(GFP_NOFS, 1);
 
 	bio->bi_iter.bi_sector = bp->l_blkno << (log->l2bsize - 9);
-	bio_set_dev(bio, log->bdev);
+	if (log->bdev != NULL)
+		bio_set_dev(bio, log->bdev);
 
 	bio_add_page(bio, bp->l_page, LOGPSIZE, bp->l_offset);
 	BUG_ON(bio->bi_iter.bi_size != LOGPSIZE);
@@ -2127,7 +2128,8 @@ static void lbmStartIO(struct lbuf * bp)
 
 	bio = bio_alloc(GFP_NOFS, 1);
 	bio->bi_iter.bi_sector = bp->l_blkno << (log->l2bsize - 9);
-	bio_set_dev(bio, log->bdev);
+	if (log->bdev != NULL)
+		bio_set_dev(bio, log->bdev);
 
 	bio_add_page(bio, bp->l_page, LOGPSIZE, bp->l_offset);
 	BUG_ON(bio->bi_iter.bi_size != LOGPSIZE);
-- 
2.25.1