[FFmpeg-cvslog] avcodec/h264: Check mode before considering mixed mode intra prediction

[Michael Niedermayer]

ffmpeg | branch: release/1.1 | Michael Niedermayer <michaelni at gmx.at> | Sat Oct  4 14:51:46 2014 +0200| [f6cfd160ca45fa8402336d47199af8dc1ad23b3e] | committer: Michael Niedermayer

avcodec/h264: Check mode before considering mixed mode intra prediction

Fixes out of array read
Fixes: asan_heap-oob_e476fc_2_asan_heap-oob_1333ec6_61_CAMACI3_Sony_C.jsv

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
(cherry picked from commit 9734a7a1de3043f012ad0f1ef11027d9488067e6)

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f6cfd160ca45fa8402336d47199af8dc1ad23b3e
---

 libavcodec/h264.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index 9599b14..66ca83f 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -163,18 +163,18 @@ int ff_h264_check_intra_pred_mode(H264Context *h, int mode, int is_chroma)
 
     if ((h->left_samples_available & 0x8080) != 0x8080) {
         mode = left[mode];
-        if (is_chroma && (h->left_samples_available & 0x8080)) {
-            // mad cow disease mode, aka MBAFF + constrained_intra_pred
-            mode = ALZHEIMER_DC_L0T_PRED8x8 +
-                   (!(h->left_samples_available & 0x8000)) +
-                   2 * (mode == DC_128_PRED8x8);
-        }
         if (mode < 0) {
             av_log(h->s.avctx, AV_LOG_ERROR,
                    "left block unavailable for requested intra mode at %d %d\n",
                    s->mb_x, s->mb_y);
             return -1;
         }
+        if (is_chroma && (h->left_samples_available & 0x8080)) {
+            // mad cow disease mode, aka MBAFF + constrained_intra_pred
+            mode = ALZHEIMER_DC_L0T_PRED8x8 +
+                   (!(h->left_samples_available & 0x8000)) +
+                   2 * (mode == DC_128_PRED8x8);
+        }
     }
 
     return mode;