[PATCH] drm: integer overflow in drm_mode_dirtyfb_ioctl()

[Eugene Teo]

Cc'ed Dave's work email.

On Wed, Nov 23, 2011 at 2:12 PM, Xi Wang <xi.wang at gmail.com> wrote:
> 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>
> ---
>  drivers/gpu/drm/drm_crtc.c |    4 ++++
>  include/drm/drm_mode.h     |    2 ++
>  2 files changed, 6 insertions(+), 0 deletions(-)
>
> 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.
>  *
> --
> 1.7.5.4
>