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@xxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
---
include/uapi/drm/drm_mode.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 550811712f78..28acbaf4a81e 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -223,6 +223,8 @@ struct drm_mode_get_connector {
__u32 connection;
__u32 mm_width, mm_height; /**< HxW in millimeters */
__u32 subpixel;
+
+ __u32 pad;
};
#define DRM_MODE_PROP_PENDING (1<<0)
--
1.8.4.rc3
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