Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 31 May 2023 00:21:50 +0200
From:   Andi Shyti <andi.shyti@kernel.org>
To:     Min Li <lm0963hack@gmail.com>
Cc:     inki.dae@samsung.com, sw0312.kim@samsung.com,
        kyungmin.park@samsung.com, airlied@gmail.com, daniel@ffwll.ch,
        krzysztof.kozlowski@linaro.org, alim.akhtar@samsung.com,
        dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/exynos: fix race condition UAF in
 exynos_g2d_exec_ioctl
Message-ID: <20230530222150.24oogloda6wtvpvm@intel.intel>
References: <20230526130131.16521-1-lm0963hack@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230526130131.16521-1-lm0963hack@gmail.com>
Precedence: bulk

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@gmail.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
>