linux-kernel - Re: [PATCH 1/7] drm/msm: fix use-after-free on probe deferral

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Date:   Mon, 12 Sep 2022 20:52:44 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Johan Hovold <johan+linaro@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Sean Paul <sean@...rly.run>,
        Stephen Boyd <swboyd@...omium.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/7] drm/msm: fix use-after-free on probe deferral

On 12/09/2022 18:40, Johan Hovold wrote:
> The bridge counter was never reset when tearing down the DRM device so
> that stale pointers to deallocated structures would be accessed on the
> next tear down (e.g. after a second late bind deferral).
> 
> Given enough bridges and a few probe deferrals this could currently also
> lead to data beyond the bridge array being corrupted.
> 
> Fixes: d28ea556267c ("drm/msm: properly add and remove internal bridges")
> Cc: stable@...r.kernel.org      # 5.19

Fixes: a3376e3ec81c ("drm/msm: convert to drm_bridge")
Cc: stable@...r.kernel.org # 3.12

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>   drivers/gpu/drm/msm/msm_drv.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 391d86b54ded..d254fe2507ec 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -241,6 +241,7 @@ static int msm_drm_uninit(struct device *dev)
>   
>   	for (i = 0; i < priv->num_bridges; i++)
>   		drm_bridge_remove(priv->bridges[i]);
> +	priv->num_bridges = 0;
>   
>   	pm_runtime_get_sync(dev);
>   	msm_irq_uninstall(ddev);

-- 
With best wishes
Dmitry