[PATCH 6.6 271/301] drm/vmwgfx: Fix invalid reads in fence signaled events

[Greg Kroah-Hartman]

6.6-stable review patch.  If anyone has any objections, please let me know.

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

From: Zack Rusin <zack.rusin@xxxxxxxxxxxx>

commit a37ef7613c00f2d72c8fc08bd83fb6cc76926c8c upstream.

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 <zack.rusin@xxxxxxxxxxxx>
Fixes: 8b7de6aa8468 ("vmwgfx: Rework fence event action")
Reported-by: zdi-disclosures@xxxxxxxxxxxxxx # ZDI-CAN-23566
Cc: David Airlie <airlied@xxxxxxxxx>
CC: Daniel Vetter <daniel@xxxxxxxx>
Cc: Zack Rusin <zack.rusin@xxxxxxxxxxxx>
Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@xxxxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v3.4+
Reviewed-by: Maaz Mombasawala <maaz.mombasawala@xxxxxxxxxxxx>
Reviewed-by: Martin Krastev <martin.krastev@xxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20240425192748.1761522-1-zack.rusin@xxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_fence.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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
 	}
 
 	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);