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avcodec/h264_parser: Fix undefined left shift 

Use an uint32_t for the NAL unit size of an AVC H.264 NAL unit instead
of an int as a left shift of a signed value is undefined behaviour
if the result doesn't fit into the target type.

Also make the log message never output negative lengths.

Fixes: left shift of 16711968 by 8 places cannot be represented in type 'int'
Fixes: 36601/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_H264_fuzzer-6581933285965824

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2020-05-26 20:26:28 +02:00
parent 29bf3fafa0
commit c83a7dd25f
1 changed files with 4 additions and 3 deletions
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7
libavcodec/h264_parser.c
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@ -83,12 +83,13 @@ static int h264_find_frame_end(H264ParseContext *p, const uint8_t *buf,
for (i = 0; i < buf_size; i++) {
if (i >= next_avc) {
int nalsize = 0;
uint32_t nalsize = 0;
i = next_avc;
for (j = 0; j < p->nal_length_size; j++)
nalsize = (nalsize << 8) | buf[i++];
if (nalsize <= 0 || nalsize > buf_size - i) {
av_log(logctx, AV_LOG_ERROR, "AVC-parser: nal size %d remaining %d\n", nalsize, buf_size - i);
if (!nalsize || nalsize > buf_size - i) {
av_log(logctx, AV_LOG_ERROR, "AVC-parser: nal size %"PRIu32" "
"remaining %d\n", nalsize, buf_size - i);
return buf_size;
}
next_avc = i + nalsize;