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matroskadec: Fix overflow introduced in a569a7b3

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This commit fixes an overflow introduced in a569a7b3 that affected EBML
elements that the Matroska demuxer doesn't want to parse like CRC-32
elements. The return value of avio_skip (the new position on success or
an AVERROR on failure) has been assigned to an integer which meant that
new positions in the range of 2GB to 4GB-1 etc. were considered errors.

Fixes ticket #8001.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2019-07-06 18:59:22 +02:00 committed by James Almer
parent b9a6106842
commit eb33be188d
1 changed files with 4 additions and 2 deletions
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6
libavformat/matroskadec.c
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@ -1259,12 +1259,13 @@ static int ebml_parse_elem(MatroskaDemuxContext *matroska,
return 1;
default:
if (length) {
int64_t res2;
if (ffio_limit(pb, length) != length) {
// ffio_limit emits its own error message,
// so we don't have to.
return AVERROR(EIO);
}
if ((res = avio_skip(pb, length - 1)) >= 0) {
if ((res2 = avio_skip(pb, length - 1)) >= 0) {
// avio_skip might take us past EOF. We check for this
// by skipping only length - 1 bytes, reading a byte and
// checking the error flags. This is done in order to check
@ -1272,7 +1273,8 @@ static int ebml_parse_elem(MatroskaDemuxContext *matroska,
// no filesize (that ffio_limit relies on) is available.
avio_r8(pb);
res = NEEDS_CHECKING;
}
} else
res = res2;
} else
res = 0;
}