[PATCH AUTOSEL 5.8 58/72] md: raid0/linear: fix dereference before null check on pointer mddev

[Sasha Levin]

From: Colin Ian King <colin.k...@canonical.com>

[ 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.k...@canonical.com>
Reviewed-by: Guilherme G. Piccoli <gpicc...@canonical.com>
Signed-off-by: Song Liu <songliubrav...@fb.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/md/md.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index f567f536b529b..90756450b9588 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -470,17 +470,18 @@ static blk_qc_t md_make_request(struct request_queue *q, 
struct bio *bio)
        struct mddev *mddev = bio->bi_disk->private_data;
        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;
-- 
2.25.1