[SRU][T/A][PATCH 1/1] cdrom: information leak in cdrom_ioctl_media_changed()

[Khalid Elmously]

From: Dan Carpenter <dan.carpenter at oracle.com>

CVE-2018-10940

This cast is wrong.  "cdi->capacity" is an int and "arg" is an unsigned
long.  The way the check is written now, if one of the high 32 bits is
set then we could read outside the info->slots[] array.

This bug is pretty old and it predates git.

Reviewed-by: Christoph Hellwig <hch at lst.de>
Cc: stable at vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(cherry-picked from 9de4ee40547fd315d4a0ed1dd15a2fa3559ad707)
Signed-off-by: Khalid Elmously <khalid.elmously 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 a7f37f104d6c..589a770f4270 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2374,7 +2374,7 @@ static int cdrom_ioctl_media_changed(struct cdrom_device_info *cdi,
 	if (!CDROM_CAN(CDC_SELECT_DISC) || arg == CDSL_CURRENT)
 		return media_changed(cdi, 1);
 
-	if ((unsigned int)arg >= cdi->capacity)
+	if (arg >= cdi->capacity)
 		return -EINVAL;
 
 	info = kmalloc(sizeof(*info), GFP_KERNEL);
-- 
2.17.1