linux-kernel - Re: [PATCH 2/7] drm/msm: fix memory corruption with too many bridges

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Date:   Mon, 12 Sep 2022 20:55:55 +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 2/7] drm/msm: fix memory corruption with too many bridges

On 12/09/2022 18:40, Johan Hovold wrote:
> Add the missing sanity checks on the bridge counter to avoid corrupting
> data beyond the fixed-sized bridge array in case there are ever more
> than eight bridges.
> 
> a3376e3ec81c ("drm/msm: convert to drm_bridge")
> ab5b0107ccf3 ("drm/msm: Initial add eDP support in msm drm driver (v5)")
> a689554ba6ed ("drm/msm: Initial add DSI connector support")

Most probably you've missed the Fixes: here.

> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display enable and disable")
> Cc: stable@...r.kernel.org	# 3.12
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 6 ++++++
>   drivers/gpu/drm/msm/dsi/dsi.c       | 6 ++++++
>   drivers/gpu/drm/msm/hdmi/hdmi.c     | 5 +++++

Could you please split this into respective dp/dsi/hdmi patches. This 
will assist both the review and the stable team.

Otherwise LGTM.

>   3 files changed, 17 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 3e284fed8d30..fbe950edaefe 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1604,6 +1604,12 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>   		return -EINVAL;
>   
>   	priv = dev->dev_private;
> +
> +	if (priv->num_bridges == ARRAY_SIZE(priv->bridges)) {
> +		DRM_DEV_ERROR(dev->dev, "too many bridges\n");
> +		return -ENOSPC;
> +	}
> +
>   	dp_display->drm_dev = dev;
>   
>   	dp_priv = container_of(dp_display, struct dp_display_private, dp_display);
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.c b/drivers/gpu/drm/msm/dsi/dsi.c
> index 39bbabb5daf6..8a95c744972a 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi.c
> @@ -218,6 +218,12 @@ int msm_dsi_modeset_init(struct msm_dsi *msm_dsi, struct drm_device *dev,
>   		return -EINVAL;
>   
>   	priv = dev->dev_private;
> +
> +	if (priv->num_bridges == ARRAY_SIZE(priv->bridges)) {
> +		DRM_DEV_ERROR(dev->dev, "too many bridges\n");
> +		return -ENOSPC;
> +	}
> +
>   	msm_dsi->dev = dev;
>   
>   	ret = msm_dsi_host_modeset_init(msm_dsi->host, dev);
> diff --git a/drivers/gpu/drm/msm/hdmi/hdmi.c b/drivers/gpu/drm/msm/hdmi/hdmi.c
> index 93fe61b86967..a0ed6aa8e4e1 100644
> --- a/drivers/gpu/drm/msm/hdmi/hdmi.c
> +++ b/drivers/gpu/drm/msm/hdmi/hdmi.c
> @@ -300,6 +300,11 @@ int msm_hdmi_modeset_init(struct hdmi *hdmi,
>   	struct platform_device *pdev = hdmi->pdev;
>   	int ret;
>   
> +	if (priv->num_bridges == ARRAY_SIZE(priv->bridges)) {
> +		DRM_DEV_ERROR(dev->dev, "too many bridges\n");
> +		return -ENOSPC;
> +	}
> +
>   	hdmi->dev = dev;
>   	hdmi->encoder = encoder;
>   

-- 
With best wishes
Dmitry