agp: info leak in agpioc_info_wrap()

On 64 bit systems the agp_info struct has a 4 byte hole between
->agp_mode and ->aper_base.  We need to clear it to avoid disclosing
stack information to userspace.

Signed-off-by: Dan Carpenter <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Daniel Vetter <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/char/agp/frontend.c

@@ -730,6 +730,7 @@ static int agpioc_info_wrap(struct agp_file_private *priv, void __user *arg)
 
 	agp_copy_info(agp_bridge, &kerninfo);
 
+	memset(&userinfo, 0, sizeof(userinfo));
 	userinfo.version.major = kerninfo.version.major;
 	userinfo.version.minor = kerninfo.version.minor;
 	userinfo.bridge_id = kerninfo.device->vendor |