Re: [PATCH] drm/exynos: fix race condition UAF in exynos_g2d_exec_ioctl

[Andi Shyti]

Hi Min,

On Fri, May 26, 2023 at 09:01:31PM +0800, Min Li wrote:
> If it is async, runqueue_node is freed in g2d_runqueue_worker on another
> worker thread. So in extreme cases, if g2d_runqueue_worker runs first, and
> then executes the following if statement, there will be use-after-free.
> 
> Signed-off-by: Min Li <lm0963hack@xxxxxxxxx>
> ---
>  drivers/gpu/drm/exynos/exynos_drm_g2d.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> index ec784e58da5c..414e585ec7dd 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> @@ -1335,7 +1335,7 @@ int exynos_g2d_exec_ioctl(struct drm_device *drm_dev, void *data,
>  	/* Let the runqueue know that there is work to do. */
>  	queue_work(g2d->g2d_workq, &g2d->runqueue_work);
>  
> -	if (runqueue_node->async)
> +	if (req->async)

did you actually hit this? If you did, then the fix is not OK.

Andi

>  		goto out;
>  
>  	wait_for_completion(&runqueue_node->complete);
> -- 
> 2.34.1
>