md: raid0/linear: fix dereference before null check on pointer mddev

BugLink: https://bugs.launchpad.net/bugs/1892417
[ Upstream commit 9a5a85972c073f720d81a7ebd08bfe278e6e16db ]

Pointer mddev is being dereferenced with a test_bit call before mddev
is being null checked, this may cause a null pointer dereference. Fix
this by moving the null pointer checks to sanity check mddev before
it is dereferenced.

Addresses-Coverity: ("Dereference before null check")
Fixes: 62f7b1989c02 ("md raid0/linear: Mark array as 'broken' and fail BIOs if a member is gone")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Guilherme G. Piccoli <gpiccoli@canonical.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5a378a453a2d45feefa5cef6700386beb236c26c..acef01e519d06ab58ad6fea7fe5ab8bbf814e3b8 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -376,17 +376,18 @@ static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio)
        struct mddev *mddev = q->queuedata;
        unsigned int sectors;
 
-       if (unlikely(test_bit(MD_BROKEN, &mddev->flags)) && (rw == WRITE)) {
+       if (mddev == NULL || mddev->pers == NULL) {
                bio_io_error(bio);
                return BLK_QC_T_NONE;
        }
 
-       blk_queue_split(q, &bio);
-
-       if (mddev == NULL || mddev->pers == NULL) {
+       if (unlikely(test_bit(MD_BROKEN, &mddev->flags)) && (rw == WRITE)) {
                bio_io_error(bio);
                return BLK_QC_T_NONE;
        }
+
+       blk_queue_split(q, &bio);
+
        if (mddev->ro == 1 && unlikely(rw == WRITE)) {
                if (bio_sectors(bio) != 0)
                        bio->bi_status = BLK_STS_IOERR;