[PATCH] drm: make drm_get_format_name atomic/irq safe again

[Ville Syrjälä]

On Fri, Nov 04, 2016 at 11:32:45AM -0400, Rob Clark wrote:
> Fixes: 90844f00049e9f42573fd31d7c32e8fd31d3fd07
> 
>     drm: make drm_get_format_name thread-safe
> 
>     Signed-off-by: Eric Engestrom <eric at engestrom.ch>
>     [danvet: Clarify that the returned pointer must be freed with
>     kfree().]
>     Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> Note: I think we need to be a bit careful about follow-up audits of
> callers of this..  now that you need to kfree the return value I think
> it is fairly easy for new patches to introduce new callers which leak
> the return value.  We probably should have left the function as-is and
> introduce a new variant, or something like that.
> 
> Signed-off-by: Rob Clark <robdclark at gmail.com>
> ---
>  drivers/gpu/drm/drm_fourcc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index cbb8b77..2be9ea8 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -87,7 +87,10 @@ EXPORT_SYMBOL(drm_mode_legacy_fb_format);
>   */
>  char *drm_get_format_name(uint32_t format)
>  {
> -	char *buf = kmalloc(32, GFP_KERNEL);
> +	char *buf = kmalloc(32, GFP_ATOMIC);
> +
> +	if (!buf)
> +		return NULL;
>  
>  	snprintf(buf, 32,
>  		 "%c%c%c%c %s-endian (0x%08x)",

Why aren't we using kasprintf()?

Or we could have just made the caller provide the buffer...

> -- 
> 2.7.4
> 
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-- 
Ville Syrjälä
Intel OTC