[ Upstream commit e5017716adb8aa5c01c52386c1b7470101ffe9c5 ]

The "index + count" addition can overflow.  Both come directly from the
user.  This bug leads to an information leak.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Cc: Peter Malone <peter.malone@gmail.com>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Mathieu Malaterre <malat@debian.org>
Signed-off-by: NBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>