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@yandex.ru Signed-off-by: Mikhail Ivanov iwanov-23@bk.ru Signed-off-by: Pavel Koshutin koshutin.pavel@yandex.ru Signed-off-by: Artem Sadovnikov ancowi69@gmail.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);