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

commit 60f207a5 upstream.

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: df63b999 ("drm/atomic: Add for_each_{connector,crtc,plane}_in_state helper macros")
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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); 	\
 	     (__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_ */