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

[Dmitry Baryshkov]

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@xxxxxxxxxxxxxxx      # 5.19

Fixes: a3376e3ec81c ("drm/msm: convert to drm_bridge")
Cc: stable@xxxxxxxxxxxxxxx # 3.12

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

> Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> ---
>   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