[PATCH 3.4 49/92] drm: crtc: integer overflow in drm_property_create_blob()

[lizf]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

3.4.112-rc1 review patch.  If anyone has any objections, please let me know.

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


commit 9ac0934bbe52290e4e4c2a58ec41cab9b6ca8c96 upstream.

The size here comes from the user via the ioctl, it is a number between
1-u32max so the addition here could overflow on 32 bit systems.

Fixes: f453ba046074 ('DRM: add mode setting support')
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: Daniel Stone <daniels@xxxxxxxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxx>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index ed4b748..93c5b2f 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2945,7 +2945,7 @@ static struct drm_property_blob *drm_property_create_blob(struct drm_device *dev
 	struct drm_property_blob *blob;
 	int ret;
 
-	if (!length || !data)
+	if (!length || length > ULONG_MAX - sizeof(struct drm_property_blob) || !data)
 		return NULL;
 
 	blob = kzalloc(sizeof(struct drm_property_blob)+length, GFP_KERNEL);
-- 
1.9.1