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| author | Michael Niedermayer <michael@niedermayer.cc> | 2019-01-08 18:11:47 +0100 |
|---|---|---|
| committer | Michael Niedermayer <michael@niedermayer.cc> | 2019-01-16 01:29:18 +0100 |
| commit | 6dde65d7c0ac34ad1aa2619ec7d979cb6464f9af (patch) | |
| tree | a36a4d5b273f0ccb71148f95ee5490960f2edf00 | |
| parent | 19dc5cdaa7c4a0e62c30497814417ffe77fb2ed7 (diff) | |
| download | ffmpeg-6dde65d7c0ac34ad1aa2619ec7d979cb6464f9af.tar.gz | |
avcodec/ac3dec: Optimize frame start search
Fixes: Timeout
Fixes: 11619/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AC3_FIXED_fuzzer-5632398021099520
Fixes: 11620/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AC3_fuzzer-5711996515778560
Fixes: 11658/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EAC3_fuzzer-5701006524940288
Before: Executed clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AC3_FIXED_fuzzer-5632398021099520 in 20338 ms
After: Executed clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AC3_FIXED_fuzzer-5632398021099520 in 11825 ms
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
| -rw-r--r-- | libavcodec/ac3dec.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c index ba731314b4..f844a463ee 100644 --- a/libavcodec/ac3dec.c +++ b/libavcodec/ac3dec.c @@ -1467,6 +1467,7 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int buf_size, full_buf_size = avpkt->size; AC3DecodeContext *s = avctx->priv_data; int blk, ch, err, offset, ret; + int i; int skip = 0, got_independent_frame = 0; const uint8_t *channel_map; uint8_t extended_channel_map[EAC3_MAX_CHANNELS]; @@ -1477,14 +1478,21 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, s->superframe_size = 0; buf_size = full_buf_size; - while (buf_size > 2) { - if (AV_RB16(buf) != 0x770B && AV_RL16(buf) != 0x770B) { - buf += 1; - buf_size -= 1; - continue; + for (i = 1; i < buf_size; i += 2) { + if (buf[i] == 0x77 || buf[i] == 0x0B) { + if ((buf[i] ^ buf[i-1]) == (0x77 ^ 0x0B)) { + i--; + break; + } else if ((buf[i] ^ buf[i+1]) == (0x77 ^ 0x0B)) { + break; + } } - break; } + if (i >= buf_size) + return AVERROR_INVALIDDATA; + buf += i; + buf_size -= i; + /* copy input buffer to decoder context to avoid reading past the end of the buffer, which can be caused by a damaged input stream. */ if (buf_size >= 2 && AV_RB16(buf) == 0x770B) { |