[FFmpeg-cvslog] avcodec/ac3: Explicitly return to discard large amounts of nonsense bytes

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Jan 31 00:45:51 2019 +0100| [1e59071aad9582fd2ef53b3e9c0dcf4ee913af0f] | committer: Michael Niedermayer

avcodec/ac3: Explicitly return to discard large amounts of nonsense bytes

Changes 19sec to 10ms (12559) runtime, 17sec to 177ms (12570)
Fixes: Timeout
Fixes: 12559/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AC3_fuzzer-5666516266123264
Fixes: 12561/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AC3_FIXED_fuzzer-5682923041193984
Fixes: 12570/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EAC3_fuzzer-5194734308425728

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=1e59071aad9582fd2ef53b3e9c0dcf4ee913af0f
---

 libavcodec/ac3dec.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index f844a463ee..eaa327a3ee 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -1490,6 +1490,8 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data,
     }
     if (i >= buf_size)
         return AVERROR_INVALIDDATA;
+    if (i > 10)
+        return i;
     buf += i;
     buf_size -= i;