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rm: prevent infinite loops for index parsing.

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Specifically, prevent jumping back in the file for the next index, since
this can lead to infinite loops where we jump between indexes referring
to each other, and don't read indexes that don't fit in the file.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
This commit is contained in:
Ronald S. Bultje 2012-02-22 11:33:24 -08:00
parent 1cd9a6154b
commit aac07a7a4c
1 changed files with 17 additions and 3 deletions
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20
libavformat/rmdec.c
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@ -370,8 +370,19 @@ static int rm_read_index(AVFormatContext *s)
st = s->streams[n];
break;
}
if (n == s->nb_streams)
if (n == s->nb_streams) {
av_log(s, AV_LOG_ERROR,
"Invalid stream index %d for index at pos %"PRId64"\n",
str_id, avio_tell(pb));
goto skip;
} else if ((avio_size(pb) - avio_tell(pb)) / 14 < n_pkts) {
av_log(s, AV_LOG_ERROR,
"Nr. of packets in packet index for stream index %d "
"exceeds filesize (%"PRId64" at %"PRId64" = %d)\n",
str_id, avio_size(pb), avio_tell(pb),
(avio_size(pb) - avio_tell(pb)) / 14);
goto skip;
}
for (n = 0; n < n_pkts; n++) {
avio_skip(pb, 2);
@ -383,9 +394,12 @@ static int rm_read_index(AVFormatContext *s)
}
skip:
if (next_off && avio_tell(pb) != next_off &&
avio_seek(pb, next_off, SEEK_SET) < 0)
if (next_off && avio_tell(pb) < next_off &&
avio_seek(pb, next_off, SEEK_SET) < 0) {
av_log(s, AV_LOG_ERROR,
"Non-linear index detected, not supported\n");
return -1;
}
} while (next_off);
return 0;