From e83f27a21a6d2f602b55e541ef66e365400e9827 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Thu, 12 Nov 2020 16:13:48 +0100 Subject: [PATCH] avformat/asfdec_o: Don't segfault with lots of attached pics The ASF file format has a limit of 127 streams and the "asf_o" demuxer (the ASF demuxer from Libav) has an array of pointers for a structure called ASFStream that is allocated on demand for every stream. Attached pictures are not streams in the sense of the ASF specification, yet the demuxer created an ASFStream for them; and in one codepath it also forgot to check whether the array of ASFStreams is already full. The result is a write beyond the end of the array and a segfault lateron. Fixing this is easy: Don't create ASFStreams for attached picture streams. (Other results of the current state of affairs are unnecessary allocations (of ASFStreams structures), the misparsing of valid files (there might not be enough ASFStreams left for the valid streams if attached pictures take up too many); furthermore, the ASFStreams created for attached pictures all have the stream number 0, an invalid stream number (the valid range is 1-127). This means that invalid data (packets for a stream with stream number 0) won't get rejected lateron.) Signed-off-by: Andreas Rheinhardt --- libavformat/asfdec_o.c | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/libavformat/asfdec_o.c b/libavformat/asfdec_o.c index b142f83541..0a7e47d8cc 100644 --- a/libavformat/asfdec_o.c +++ b/libavformat/asfdec_o.c @@ -357,7 +357,6 @@ static int asf_set_metadata(AVFormatContext *s, const uint8_t *name, * but in reality this is only loosely similar */ static int asf_read_picture(AVFormatContext *s, int len) { - ASFContext *asf = s->priv_data; AVPacket pkt = { 0 }; const CodecMime *mime = ff_id3v2_mime_tags; enum AVCodecID id = AV_CODEC_ID_NONE; @@ -365,7 +364,6 @@ static int asf_read_picture(AVFormatContext *s, int len) uint8_t *desc = NULL; AVStream *st = NULL; int ret, type, picsize, desc_len; - ASFStream *asf_st; /* type + picsize + mime + desc */ if (len < 1 + 4 + 2 + 2) { @@ -422,22 +420,14 @@ static int asf_read_picture(AVFormatContext *s, int len) ret = AVERROR(ENOMEM); goto fail; } - asf->asf_st[asf->nb_streams] = av_mallocz(sizeof(*asf_st)); - asf_st = asf->asf_st[asf->nb_streams]; - if (!asf_st) { - ret = AVERROR(ENOMEM); - goto fail; - } st->disposition |= AV_DISPOSITION_ATTACHED_PIC; - st->codecpar->codec_type = asf_st->type = AVMEDIA_TYPE_VIDEO; + st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO; st->codecpar->codec_id = id; st->attached_pic = pkt; - st->attached_pic.stream_index = asf_st->index = st->index; + st->attached_pic.stream_index = st->index; st->attached_pic.flags |= AV_PKT_FLAG_KEY; - asf->nb_streams++; - if (*desc) { if (av_dict_set(&st->metadata, "title", desc, AV_DICT_DONT_STRDUP_VAL) < 0) av_log(s, AV_LOG_WARNING, "av_dict_set failed.\n");