drm/vmwgfx: Fix invalid reads in fence signaled events

Correctly set the length of the drm_event to the size of the structure
that's actually used.

The length of the drm_event was set to the parent structure instead of
to the drm_vmw_event_fence which is supposed to be read. drm_read
uses the length parameter to copy the event to the user space thus
resuling in oob reads.

Signed-off-by: Zack Rusin <[email protected]>
Fixes: 8b7de6aa8468 ("vmwgfx: Rework fence event action")
Reported-by: [email protected] # ZDI-CAN-23566
Cc: David Airlie <[email protected]>
CC: Daniel Vetter <[email protected]>
Cc: Zack Rusin <[email protected]>
Cc: Broadcom internal kernel review list <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: <[email protected]> # v3.4+
Reviewed-by: Maaz Mombasawala <[email protected]>
Reviewed-by: Martin Krastev <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
index 2a0cda324703147ef36ff83cd891c70c3395c11d..5efc6a766f64e467a68223376b2a97aa62b278e6 100644 (file)
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
@@ -991,7 +991,7 @@ static int vmw_event_fence_action_create(struct drm_file *file_priv,
        }
 
        event->event.base.type = DRM_VMW_EVENT_FENCE_SIGNALED;
-       event->event.base.length = sizeof(*event);
+       event->event.base.length = sizeof(event->event);
        event->event.user_data = user_data;
 
        ret = drm_event_reserve_init(dev, file_priv, &event->base, &event->event.base);