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

[Martin Krastev]

LGTM!

Reviewed-by: Martin Krastev <martin.krastev at broadcom.com>

Regards,
Martin

On Thu, Apr 25, 2024 at 10:27 PM Zack Rusin <zack.rusin at broadcom.com> wrote:
>
> 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 at broadcom.com>
> Fixes: 8b7de6aa8468 ("vmwgfx: Rework fence event action")
> Reported-by: zdi-disclosures at trendmicro.com # ZDI-CAN-23566
> Cc: David Airlie <airlied at gmail.com>
> CC: Daniel Vetter <daniel at ffwll.ch>
> Cc: Zack Rusin <zack.rusin at broadcom.com>
> Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list at broadcom.com>
> Cc: dri-devel at lists.freedesktop.org
> Cc: linux-kernel at vger.kernel.org
> Cc: <stable at vger.kernel.org> # v3.4+
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_fence.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
> index 2a0cda324703..5efc6a766f64 100644
> --- 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);
> --
> 2.40.1
>