[FFmpeg-cvslog] avcodec/vp8: Move end check into MB loop in vp78_decode_mv_mb_modes()

[Michael Niedermayer]

ffmpeg | branch: release/4.3 | Michael Niedermayer <michael at niedermayer.cc> | Mon Feb 15 17:13:34 2021 +0100| [c4ae8618f46e1c2909ae2f88ab5ef7995278cf75] | committer: Michael Niedermayer

avcodec/vp8: Move end check into MB loop in vp78_decode_mv_mb_modes()

Fixes: Timeout (long -> 5sec)
Fixes: 30269/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP7_fuzzer-5430325004075008

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Peter Ross <pross at xvid.org>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 6a797ceafe2a96aa1682a1eca421eddd4c498275)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c4ae8618f46e1c2909ae2f88ab5ef7995278cf75
---

 libavcodec/vp8.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libavcodec/vp8.c b/libavcodec/vp8.c
index bab4223aca..e84fcdeaa1 100644
--- a/libavcodec/vp8.c
+++ b/libavcodec/vp8.c
@@ -2289,10 +2289,10 @@ int vp78_decode_mv_mb_modes(AVCodecContext *avctx, VP8Frame *curframe,
         s->mv_bounds.mv_min.x = -MARGIN;
         s->mv_bounds.mv_max.x = ((s->mb_width - 1) << 6) + MARGIN;
 
-        if (vpX_rac_is_end(&s->c)) {
-            return AVERROR_INVALIDDATA;
-        }
         for (mb_x = 0; mb_x < s->mb_width; mb_x++, mb_xy++, mb++) {
+            if (vpX_rac_is_end(&s->c)) {
+                return AVERROR_INVALIDDATA;
+            }
             if (mb_y == 0)
                 AV_WN32A((mb - s->mb_width - 1)->intra4x4_pred_mode_top,
                          DC_PRED * 0x01010101);