Re: [PATCH] drm: Reject unknown legacy bpp and depth for drm_mode_addfb ioctl

Chris Wilson
2018-09-05T10:29:56Z

Quoting Chris Wilson (2018-09-05 11:22:05)
> Since this is handling user provided bpp and depth, we need to sanity
> check and propagate the EINVAL back rather than assume what the insane
> client intended and fill the logs with DRM_ERROR.
>
> v2: Check both bpp and depth match the builtin pixel format, and
> introduce a canonical DRM_FORMAT_INVALID to reserve 0 against any future
> fourcc.
>
> Testcase: igt/kms_addfb_basic/legacy-format
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/drm_fourcc.c | 33 +++++++++++++++++++++----------
> drivers/gpu/drm/drm_framebuffer.c | 7 ++++++-
> include/uapi/drm/drm_fourcc.h | 3 +++
> 3 files changed, 32 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index 35c1e2742c27..d9dadbc43327 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -45,32 +45,45 @@ static char printable_char(int c)
> */
> uint32_t drm_mode_legacy_fb_format(uint32_t bpp, uint32_t depth)
> {
> - uint32_t fmt;
> + uint32_t fmt = DRM_FORMAT_INVALID;
>
> switch (bpp) {
> case 8:
> - fmt = DRM_FORMAT_C8;
> + if (depth == 0)
> + fmt = DRM_FORMAT_C8;

Of course the downside with increasing specificity is if any userspace
was already feeding in garbage depth that just happens to work :(
-Chris