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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Colin Ian King <colin.king@canonical.com>,
        "Guilherme G. Piccoli" <gpiccoli@canonical.com>,
        Song Liu <songliubraving@fb.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.8 062/464] md: raid0/linear: fix dereference before null check on pointer mddev
Date:   Mon, 17 Aug 2020 17:10:15 +0200
Message-Id: <20200817143836.734203816@linuxfoundation.org>
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From: Colin Ian King <colin.king@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.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>
---
 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