[PATCH] Media: video: uvc: integer overflow in uvc_ioctl_ctrl_map()

[Haogang Chen <haogangchen@gmail.com>]

There is a potential integer overflow in uvc_ioctl_ctrl_map(). When a
large xmap->menu_count is passed from the userspace, the subsequent call
to kmalloc() will allocate a buffer smaller than expected.
map->menu_count and map->menu_info would later be used in a loop (e.g.
in uvc_query_v4l2_ctrl), which leads to out-of-bound access.

The patch checks the ioctl argument and returns -EINVAL for zero or too
large values in xmap->menu_count.

Signed-off-by: Haogang Chen <haogangchen@gmail.com>
---
 drivers/media/video/uvc/uvc_v4l2.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/media/video/uvc/uvc_v4l2.c b/drivers/media/video/uvc/uvc_v4l2.c
index dadf11f..9a180d6 100644
--- a/drivers/media/video/uvc/uvc_v4l2.c
+++ b/drivers/media/video/uvc/uvc_v4l2.c
@@ -58,6 +58,12 @@ static int uvc_ioctl_ctrl_map(struct uvc_video_chain *chain,
 		break;
 
 	case V4L2_CTRL_TYPE_MENU:
+		if (xmap->menu_count == 0 ||
+		    xmap->menu_count > INT_MAX / sizeof(*map->menu_info)) {
+			kfree(map);
+			return -EINVAL;
+		}
+
 		size = xmap->menu_count * sizeof(*map->menu_info);
 		map->menu_info = kmalloc(size, GFP_KERNEL);
 		if (map->menu_info == NULL) {
-- 
1.7.5.4