[PATCH 4.9 081/101] media: v4l2-compat-ioctl32: prevent go past max size

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>

commit ea72fbf588ac9c017224dcdaa2019ff52ca56fee upstream.

As warned by smatch:
	drivers/media/v4l2-core/v4l2-compat-ioctl32.c:879 put_v4l2_ext_controls32() warn: check for integer overflow 'count'

The access_ok() logic should check for too big arrays too.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/media/v4l2-core/v4l2-compat-ioctl32.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -864,7 +864,7 @@ static int put_v4l2_ext_controls32(struc
 	    get_user(kcontrols, &kp->controls))
 		return -EFAULT;
 
-	if (!count)
+	if (!count || count > (U32_MAX/sizeof(*ucontrols)))
 		return 0;
 	if (get_user(p, &up->controls))
 		return -EFAULT;