[PATCH] md: fix potential OOB in multipath_remove_disk()

[Zhang Shurong]

If rddev->raid_disk is greater than mddev->raid_disks, there will be
an out-of-bounds in multipath_remove_disk. We have already found
similar reports as follows:

1) commit d17f744e883b ("md-raid10: fix KASAN warning")
2) commit 1ebc2cec0b7d ("dm raid: fix KASAN warning in raid5_remove_disk")

Fix this bug by checking whether the "number" variable is
valid.

Signed-off-by: Zhang Shurong <zhang_shurong@xxxxxxxxxxx>
---
 drivers/md/md-multipath.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/md/md-multipath.c b/drivers/md/md-multipath.c
index 92c45be203d7..7b6aadd8c1fb 100644
--- a/drivers/md/md-multipath.c
+++ b/drivers/md/md-multipath.c
@@ -245,7 +245,11 @@ static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 	struct mpconf *conf = mddev->private;
 	int err = 0;
 	int number = rdev->raid_disk;
-	struct multipath_info *p = conf->multipaths + number;
+	struct multipath_info *p;
+
+	if (unlikely(number >= mddev->raid_disks))
+		return 0;
+	p = conf->multipaths + number;
 
 	print_multipath_conf(conf);
 
-- 
2.30.2