[PATCH 3.7-rc8] drm: Fix possible EDID memory allocation oops

[Alex Deucher]

On Wed, Dec 5, 2012 at 2:00 PM, Tim Gardner <tim.gardner at canonical.com> wrote:
> The result of drm_property_create_blob() is not checked for success
> which could lead to a NULL pointer dereference.
>
> I was led to this by a smatch warning:
>
> drivers/gpu/drm/drm_crtc.c:3186 drm_mode_connector_update_edid_property() error: potential null dereference 'connector->edid_blob_ptr'.  (drm_property_create_blob returns null)
>
> drm_property_create_blob() calls kzalloc() which can return NULL.
>
> Cc: David Airlie <airlied at linux.ie>
> Cc: dri-devel at lists.freedesktop.org
> Cc: stable at vger.kernel.org # 3.0+
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>
> This bug actually exists in the original commit f453ba0460742ad027ae0c4c7d61e62817b3e7ef
> (2.6.29), but I only checked as far back as 3.0 for stable.
>
>  drivers/gpu/drm/drm_crtc.c |    4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index ef1b221..31872ba 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -3180,6 +3180,10 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>         size = EDID_LENGTH * (1 + edid->extensions);
>         connector->edid_blob_ptr = drm_property_create_blob(connector->dev,
>                                                             size, edid);
> +       if (!connector->edid_blob_ptr) {
> +               pr_err("drm: Could not allocate %d edid blob bytes.\n", size);
> +               return -ENOMEM;
> +       }
>
>         ret = drm_connector_property_set_value(connector,
>                                                dev->mode_config.edid_property,
> --
> 1.7.9.5
>
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