From 9a5a85972c073f720d81a7ebd08bfe278e6e16db Mon Sep 17 00:00:00 2001
From: Colin Ian King <colin.king@canonical.com>
Date: Thu, 2 Jul 2020 12:35:02 +0100
Subject: [PATCH] md: raid0/linear: fix dereference before null check on
 pointer mddev
Git-commit: 9a5a85972c073f720d81a7ebd08bfe278e6e16db
Patch-mainline: v5.9-rc1
References: git fixes (block drivers)

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: Coly Li <colyli@suse.de>

---
 drivers/md/md.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -384,17 +384,18 @@ static blk_qc_t md_make_request(struct r
 	unsigned int sectors;
 	int cpu;
 
-	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;