ffmpeg | branch: master | Aidan MacDonald <aidanmacdonald....@gmail.com> | Fri Sep 30 15:20:09 2022 +0100| [a4405cc0cc16413fe5222c888b3d4bb04cedc83f] | committer: Anton Khirnov
avcodec/dvdsub_parser: Fix length check for short packets The DVD subtitle parser handles two types of packets: "normal" packets with a 16-bit length, and HD-DVD packets that set the 16-bit length to 0 and encode a 32-bit length in the next four bytes. This implies that HD-DVD packets are at least six bytes long, but the code didn't actually verify this. The faulty length check results in an out of bounds read for zero-length "normal" packets that occur in the input, which are only 2 bytes long, but get misinterpreted as an HD-DVD packet. When this happens the parser reads packet_len from beyond the end of the input buffer. The subtitle stream is not correctly decoded after this point due to the garbage packet_len. Fixing this is pretty simple: fix the length check so packets less than 6 bytes long will not be mistakenly parsed as HD-DVD packets. Signed-off-by: Aidan MacDonald <aidanmacdonald....@gmail.com> Signed-off-by: Anton Khirnov <an...@khirnov.net> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a4405cc0cc16413fe5222c888b3d4bb04cedc83f --- libavcodec/dvdsub_parser.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libavcodec/dvdsub_parser.c b/libavcodec/dvdsub_parser.c index 44738a73d6..8871b6a383 100644 --- a/libavcodec/dvdsub_parser.c +++ b/libavcodec/dvdsub_parser.c @@ -43,7 +43,7 @@ static int dvdsub_parse(AVCodecParserContext *s, *poutbuf_size = buf_size; if (pc->packet_index == 0) { - if (buf_size < 2 || AV_RB16(buf) && buf_size < 6) { + if (buf_size < 2 || (AV_RB16(buf) == 0 && buf_size < 6)) { if (buf_size) av_log(avctx, AV_LOG_DEBUG, "Parser input %d too small\n", buf_size); return buf_size; _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog To unsubscribe, visit link above, or email ffmpeg-cvslog-requ...@ffmpeg.org with subject "unsubscribe".
