Re: [PATCH] drm: check for NULL parameter in exported drm_get_format_name() function.

[Ville Syrjälä]

On Tue, Nov 22, 2016 at 04:41:06PM +0000, Liviu Dudau wrote:
> drm_get_format_name() de-references the buf parameter without checking
> if the pointer was not NULL. Given that the function is EXPORT-ed, lets
> sanitise the parameters before proceeding.
> 
> Fixes: b3c11ac267d461d3d5 ("drm: move allocation out of drm_get_format_name())
> Cc: Eric Engestrom <eric@xxxxxxxxxxxx>
> Cc: Rob Clark <robdclark@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> 
> Signed-off-by: Liviu Dudau <Liviu.Dudau@xxxxxxx>
> ---
>  drivers/gpu/drm/drm_fourcc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index 90d2cc8..0a3ff0b 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -85,6 +85,9 @@ EXPORT_SYMBOL(drm_mode_legacy_fb_format);
>   */
>  const char *drm_get_format_name(uint32_t format, struct drm_format_name_buf *buf)
>  {
> +	if (!buf)
> +		return NULL;
> +

Seems rather pointless to me. Why would you ever pass NULL to this guy?

>  	snprintf(buf->str, sizeof(buf->str),
>  		 "%c%c%c%c %s-endian (0x%08x)",
>  		 printable_char(format & 0xff),
> -- 
> 2.10.2
> 
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-- 
Ville Syrjälä
Intel OTC