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avformat/matroskadec: Reset state also on failure in matroska_reset_status()

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The calling code does not handle failures and will fail with assertion failures later.
Seeking can always fail even when the position was previously read.

Fixes: Assertion failure
Fixes: 35253/clusterfuzz-testcase-minimized-ffmpeg_dem_MATROSKA_fuzzer-4693059982983168

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit d115eec97929e23fd1b06df2d95f48cf5000eb87)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2021-06-24 19:53:47 +02:00
parent 4069494725
commit 13044f729d
1 changed files with 12 additions and 7 deletions
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19
libavformat/matroskadec.c
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@ -778,20 +778,22 @@ static int matroska_read_close(AVFormatContext *s);
static int matroska_reset_status(MatroskaDemuxContext *matroska,
uint32_t id, int64_t position)
{
int64_t err = 0;
if (position >= 0) {
int64_t err = avio_seek(matroska->ctx->pb, position, SEEK_SET);
if (err < 0)
return err;
}
err = avio_seek(matroska->ctx->pb, position, SEEK_SET);
if (err > 0)
err = 0;
} else
position = avio_tell(matroska->ctx->pb);
matroska->current_id = id;
matroska->num_levels = 1;
matroska->unknown_count = 0;
matroska->resync_pos = avio_tell(matroska->ctx->pb);
matroska->resync_pos = position;
if (id)
matroska->resync_pos -= (av_log2(id) + 7) / 8;
return 0;
return err;
}
static int matroska_resync(MatroskaDemuxContext *matroska, int64_t last_pos)
@ -1824,6 +1826,7 @@ static int matroska_parse_seekhead_entry(MatroskaDemuxContext *matroska,
uint32_t saved_id = matroska->current_id;
int64_t before_pos = avio_tell(matroska->ctx->pb);
int ret = 0;
int ret2;
/* seek */
if (avio_seek(matroska->ctx->pb, pos, SEEK_SET) == pos) {
@ -1848,7 +1851,9 @@ static int matroska_parse_seekhead_entry(MatroskaDemuxContext *matroska,
}
/* Seek back - notice that in all instances where this is used
* it is safe to set the level to 1. */
matroska_reset_status(matroska, saved_id, before_pos);
ret2 = matroska_reset_status(matroska, saved_id, before_pos);
if (ret >= 0)
ret = ret2;
return ret;
}