[ Upstream commit 117fcc30 ]

The "drive->dn" value is a u8 and it is controlled by root only, but
it could be out of bounds here so let's check.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>