[Intel-gfx] [PATCH i-g-t 4/5] lib/igt_kms: Fix memory corruption when there's no cursor plane

[Robert Foss]

On 2017-02-17 12:54 PM, Brian Starkey wrote:
> The dynamic plane support means that if there's no cursor plane, then
> there is no space in the pipe->planes array for it, and thus assigning
> a "drm_plane-less" plane is out-of-bounds and leads to heap corruption
> and later crashes.
>
> The "drm_plane-less" cursor plane isn't included in n_planes anyway,
> which means there's no way to ever access it/know that it's there - so
> just remove it entirely.

Nice catch!

Reviewed-by: Robert Foss <robert.foss at collabora.com>


Rob.

>
> Fixes: 36656239ef96 lib/igt_kms: Implement dynamic plane count support
> Signed-off-by: Brian Starkey <brian.starkey at arm.com>
> ---
>  lib/igt_kms.c |    6 ------
>  1 file changed, 6 deletions(-)
>
> diff --git a/lib/igt_kms.c b/lib/igt_kms.c
> index 45c90c71f301..ef7bfd1a8108 100644
> --- a/lib/igt_kms.c
> +++ b/lib/igt_kms.c
> @@ -1837,12 +1837,6 @@ void igt_display_init(igt_display_t *display, int drm_fd)
>  				memset(&pipe->planes[last_plane], 0,
>  				       sizeof *plane);
>  			}
> -		} else {
> -			/* Add drm_plane-less cursor */
> -			plane = &pipe->planes[p];
> -			plane->pipe = pipe;
> -			plane->index = p;
> -			plane->type = DRM_PLANE_TYPE_CURSOR;
>  		}
>
>  		pipe->n_planes = n_planes;
>