[CVE-2018-16658][Trusty][Bionic][SRU][PATCH 1/1] cdrom: Fix info leak/OOB read in cdrom_ioctl_drive_status

[Po-Hsu Lin]

From: Scott Bauer <scott.bauer at intel.com>

CVE-2018-16658

Like d88b6d04: "cdrom: information leak in cdrom_ioctl_media_changed()"

There is another cast from unsigned long to int which causes
a bounds check to fail with specially crafted input. The value is
then used as an index in the slot array in cdrom_slot_status().

Signed-off-by: Scott Bauer <scott.bauer at intel.com>
Signed-off-by: Scott Bauer <sbauer at plzdonthack.me>
Cc: stable at vger.kernel.org
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(cherry picked from commit 8f3fafc9c2f0ece10832c25f7ffcb07c97a32ad4)
Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
---
 drivers/cdrom/cdrom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index cbee2e7..f0534a4 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2542,7 +2542,7 @@ static int cdrom_ioctl_drive_status(struct cdrom_device_info *cdi,
 	if (!CDROM_CAN(CDC_SELECT_DISC) ||
 	    (arg == CDSL_CURRENT || arg == CDSL_NONE))
 		return cdi->ops->drive_status(cdi, CDSL_CURRENT);
-	if (((int)arg >= cdi->capacity))
+	if (arg >= cdi->capacity)
 		return -EINVAL;
 	return cdrom_slot_status(cdi, arg);
 }
-- 
2.7.4