[PATCH] drm/atomic: fix out of bounds read in for_each_*_in_state helpers

[Jani Nikula]

On Mon, 25 May 2015, Andrey Ryabinin <a.ryabinin at samsung.com> wrote:
> for_each_*_in_state validate array index after
> access to array elements, thus perform out of bounds read.
>
> Fix this by validating index in the first place and read
> array element iff validation was successful.
>
> Fixes: df63b9994eaf ("drm/atomic: Add for_each_{connector,crtc,plane}_in_state helper macros")
> Signed-off-by: Andrey Ryabinin <a.ryabinin at samsung.com>
> ---
>  include/drm/drm_atomic.h | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index c1571034..3f13b91 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -77,26 +77,26 @@ int __must_check drm_atomic_async_commit(struct drm_atomic_state *state);
>  
>  #define for_each_connector_in_state(state, connector, connector_state, __i) \
>  	for ((__i) = 0;							\
> -	     (connector) = (state)->connectors[__i],			\
> -	     (connector_state) = (state)->connector_states[__i],	\
> -	     (__i) < (state)->num_connector;				\
> +	     (__i) < (state)->num_connector &&				\
> +	     ((connector) = (state)->connectors[__i],			\
> +	     (connector_state) = (state)->connector_states[__i], 1); 	\

This will stop at the first NULL connector/connector_state. Similarly
for the loops below.

BR,
Jani.

>  	     (__i)++)							\
>  		if (connector)
>  
>  #define for_each_crtc_in_state(state, crtc, crtc_state, __i)	\
>  	for ((__i) = 0;						\
> -	     (crtc) = (state)->crtcs[__i],			\
> -	     (crtc_state) = (state)->crtc_states[__i],		\
> -	     (__i) < (state)->dev->mode_config.num_crtc;	\
> +	     (__i) < (state)->dev->mode_config.num_crtc &&	\
> +	     ((crtc) = (state)->crtcs[__i],			\
> +	     (crtc_state) = (state)->crtc_states[__i], 1);	\
>  	     (__i)++)						\
>  		if (crtc_state)
>  
> -#define for_each_plane_in_state(state, plane, plane_state, __i)	\
> -	for ((__i) = 0;						\
> -	     (plane) = (state)->planes[__i],			\
> -	     (plane_state) = (state)->plane_states[__i],	\
> -	     (__i) < (state)->dev->mode_config.num_total_plane;	\
> -	     (__i)++)						\
> +#define for_each_plane_in_state(state, plane, plane_state, __i)		\
> +	for ((__i) = 0;							\
> +	     (__i) < (state)->dev->mode_config.num_total_plane &&	\
> +	     ((plane) = (state)->planes[__i],				\
> +	     (plane_state) = (state)->plane_states[__i], 1);		\
> +	     (__i)++)							\
>  		if (plane_state)
>  
>  #endif /* DRM_ATOMIC_H_ */
> -- 
> 2.4.1
>
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-- 
Jani Nikula, Intel Open Source Technology Center