[PATCH] md/raid5: fail invalid raid5_set_limits() geometry

["Chen Cheng" <chencheng@fnnas.com>]

From: Chen Cheng <chencheng@fnnas.com>

Prevent raid5_set_limits() from building a stripe size when the array
geometry reports no data disks.

Reported-by: syzbot+de94ddbfff0c9e6fe030@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=de94ddbfff0c9e6fe030
Fixes: f63f17350e537300312 ("md/raid5: use the atomic queue limit update APIs")

Signed-off-by: Chen Cheng <chencheng@fnnas.com>
---
 drivers/md/raid5.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index ffb5fcde54a9..c0adb73b1dd4 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7825,10 +7825,12 @@ static int raid5_set_limits(struct mddev *mddev)
 	/*
 	 * The read-ahead size must cover two whole stripes, which is
 	 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices.
 	 */
 	data_disks = conf->previous_raid_disks - conf->max_degraded;
+	if (data_disks <= 0)
+		return -EINVAL;
 
 	/*
 	 * We can only discard a whole stripe. It doesn't make sense to
 	 * discard data disk but write parity disk
 	 */
-- 
2.55.0