dm raid: fix KASAN warning in raid5_remove_disk

There's a KASAN warning in raid5_remove_disk when running the LVM
testsuite. We fix this warning by verifying that the "number" variable is
within limits.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

drivers/md/raid5.c

@@ -7933,7 +7933,7 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 	int err = 0;
 	int number = rdev->raid_disk;
 	struct md_rdev __rcu **rdevp;
-	struct disk_info *p = conf->disks + number;
+	struct disk_info *p;
 	struct md_rdev *tmp;
 
 	print_raid5_conf(conf);
@@ -7952,6 +7952,9 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 		log_exit(conf);
 		return 0;
 	}
+	if (unlikely(number >= conf->pool_size))
+		return 0;
+	p = conf->disks + number;
 	if (rdev == rcu_access_pointer(p->rdev))
 		rdevp = &p->rdev;
 	else if (rdev == rcu_access_pointer(p->replacement))