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

[Johan Hovold]

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")
Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display enable 
and disable")
Cc: sta...@vger.kernel.org      # 3.12
Signed-off-by: Johan Hovold <johan+lin...@kernel.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 +++++
 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;
 
-- 
2.35.1