[Acked] [lucid] [CVE-2012-0044] drm: integer overflow in drm_mode_dirtyfb_ioctl()

[Andy Whitcroft]

On Wed, Aug 08, 2012 at 03:24:00PM -0500, Steve Conklin wrote:
> From: Xi Wang <xi.wang at gmail.com>
> 
> CVE-2012-0044
> 
> BugLink: http://bugs.launchpad.net/bugs/917838
> 
> There is a potential integer overflow in drm_mode_dirtyfb_ioctl()
> if userspace passes in a large num_clips.  The call to kmalloc would
> allocate a small buffer, and the call to fb->funcs->dirty may result
> in a memory corruption.
> 
> Reported-by: Haogang Chen <haogangchen at gmail.com>
> Signed-off-by: Xi Wang <xi.wang at gmail.com>
> Cc: stable at kernel.org
> Signed-off-by: Dave Airlie <airlied at redhat.com>
> (cherry picked from commit a5cd335165e31db9dbab636fd29895d41da55dd2)
> Signed-off-by: Steve Conklin <sconklin at canonical.com>
> ---
>  drivers/gpu/drm/drm_crtc.c |    4 ++++
>  include/drm/drm_mode.h     |    2 ++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 405c63b..8323fc3 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -1873,6 +1873,10 @@ int drm_mode_dirtyfb_ioctl(struct drm_device *dev,
>  	}
>  
>  	if (num_clips && clips_ptr) {
> +		if (num_clips < 0 || num_clips > DRM_MODE_FB_DIRTY_MAX_CLIPS) {
> +			ret = -EINVAL;
> +			goto out_err1;
> +		}
>  		clips = kzalloc(num_clips * sizeof(*clips), GFP_KERNEL);
>  		if (!clips) {
>  			ret = -ENOMEM;
> diff --git a/include/drm/drm_mode.h b/include/drm/drm_mode.h
> index d30bedf..ddd46db 100644
> --- a/include/drm/drm_mode.h
> +++ b/include/drm/drm_mode.h
> @@ -235,6 +235,8 @@ struct drm_mode_fb_cmd {
>  #define DRM_MODE_FB_DIRTY_ANNOTATE_FILL 0x02
>  #define DRM_MODE_FB_DIRTY_FLAGS         0x03
>  
> +#define DRM_MODE_FB_DIRTY_MAX_CLIPS     256
> +
>  /*
>   * Mark a region of a framebuffer as dirty.
>   *
> -- 
> 1.7.9.5

Acked-by: Andy Whitcroft <apw at canonical.com>

-apw