drm: Pad drm_mode_get_connector to 64-bit boundary
authorChris Wilson <chris@chris-wilson.co.uk>
Wed, 16 Oct 2013 08:49:02 +0000 (09:49 +0100)
committerBen Hutchings <ben@decadent.org.uk>
Thu, 28 Nov 2013 14:02:05 +0000 (14:02 +0000)
commit2afe1a102cd3962ed4ec683128765fd33a4ab666
tree0822897b0af430a4eed9c8e19aacf1b24e18df11
parentb60ff9bf0fa3a0a1e5b81055383ddbef42002f18
drm: Pad drm_mode_get_connector to 64-bit boundary

commit bc5bd37ce48c66e9192ad2e7231e9678880f6f8e upstream.

Pavel Roskin reported that DRM_IOCTL_MODE_GETCONNECTOR was overwritting
the 4 bytes beyond the end of its structure with a 32-bit userspace
running on a 64-bit kernel. This is due to the padding gcc inserts as
the drm_mode_get_connector struct includes a u64 and its size is not a
natural multiple of u64s.

64-bit kernel:

sizeof(drm_mode_get_connector)=80, alignof=8
sizeof(drm_mode_get_encoder)=20, alignof=4
sizeof(drm_mode_modeinfo)=68, alignof=4

32-bit userspace:

sizeof(drm_mode_get_connector)=76, alignof=4
sizeof(drm_mode_get_encoder)=20, alignof=4
sizeof(drm_mode_modeinfo)=68, alignof=4

Fortuituously we can insert explicit padding to the tail of our
structures without breaking ABI.

Reported-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
include/drm/drm_mode.h