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avformat/mpegts: Shuffle avio_seek 

This avoids accessing an old, no longer valid buffer.
Fixes: out of array access
Fixes: crash_audio-2020

Found-by: le wu <shoulewoba@gmail.com>
Reviewed-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2020-05-07 12:38:26 +02:00
parent 5d9ce445ef
commit cd74af1416
1 changed files with 4 additions and 3 deletions
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7
libavformat/mpegts.c
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@ -2881,15 +2881,16 @@ static int mpegts_resync(AVFormatContext *s, int seekback, const uint8_t *curren
AVIOContext *pb = s->pb; AVIOContext *pb = s->pb;
int c, i; int c, i;
uint64_t pos = avio_tell(pb); uint64_t pos = avio_tell(pb);
int64_t back = FFMIN(seekback, pos);
avio_seek(pb, -FFMIN(seekback, pos), SEEK_CUR);
//Special case for files like 01c56b0dc1.ts //Special case for files like 01c56b0dc1.ts
if (current_packet[0] == 0x80 && current_packet[12] == 0x47) { if (current_packet[0] == 0x80 && current_packet[12] == 0x47) {
avio_seek(pb, 12, SEEK_CUR); avio_seek(pb, 12 - back, SEEK_CUR);
return 0; return 0;
} }
avio_seek(pb, -back, SEEK_CUR);
for (i = 0; i < ts->resync_size; i++) { for (i = 0; i < ts->resync_size; i++) {
c = avio_r8(pb); c = avio_r8(pb);
if (avio_feof(pb)) if (avio_feof(pb))