linux-kernel - Re: [PATCH] drm/exynos: fix race condition UAF in exynos_g2d_exec

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Message-ID: <20230530222150.24oogloda6wtvpvm@intel.intel>
Date:   Wed, 31 May 2023 00:21:50 +0200
From:   Andi Shyti <andi.shyti@...nel.org>
To:     Min Li <lm0963hack@...il.com>
Cc:     inki.dae@...sung.com, sw0312.kim@...sung.com,
        kyungmin.park@...sung.com, airlied@...il.com, daniel@...ll.ch,
        krzysztof.kozlowski@...aro.org, alim.akhtar@...sung.com,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/exynos: fix race condition UAF in
 exynos_g2d_exec_ioctl

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@...il.com>
> ---
>  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
>