From b51d5b222e144ed8a867c4f0d2a3eec7ad5a2497 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Thu, 1 Apr 2021 22:07:40 +0200 Subject: [PATCH] avformat/dss: Don't prematurely modify context variable The DSS demuxer currently decrements a counter that should be positive at the beginning of read_packet; should it become negative, it means that the data to be read can't be read contiguosly, but has to be read in two parts. In this case the counter is incremented again after the first read if said read succeeded; if not, the counter stays negative. This can lead to problems in further read_packet calls; in tickets #9020 and #9023 it led to segfaults if one tries to seek lateron if the seek failed and generic seek tried to read from the beginning. But it could also happen when av_new_packet() failed and the user attempted to read again afterwards. Signed-off-by: Andreas Rheinhardt (cherry picked from commit afa511ad34452b1806a6cfa2dd785168140843e6) --- libavformat/dss.c | 37 +++++++++++++++++-------------------- 1 file changed, 17 insertions(+), 20 deletions(-) diff --git a/libavformat/dss.c b/libavformat/dss.c index 0585049130..468de3fe84 100644 --- a/libavformat/dss.c +++ b/libavformat/dss.c @@ -219,7 +219,6 @@ static int dss_sp_read_packet(AVFormatContext *s, AVPacket *pkt) } else read_size = DSS_FRAME_SIZE; - ctx->counter -= read_size; ctx->packet_size = DSS_FRAME_SIZE - 1; ret = av_new_packet(pkt, DSS_FRAME_SIZE); @@ -231,17 +230,16 @@ static int dss_sp_read_packet(AVFormatContext *s, AVPacket *pkt) pkt->stream_index = 0; s->bit_rate = 8LL * ctx->packet_size * st->codecpar->sample_rate * 512 / (506 * pkt->duration); - if (ctx->counter < 0) { - int size2 = ctx->counter + read_size; - - ret = avio_read(s->pb, ctx->dss_sp_buf + offset + buff_offset, - size2 - offset); - if (ret < size2 - offset) + if (ctx->counter < read_size) { + ret = avio_read(s->pb, ctx->dss_sp_buf + buff_offset, + ctx->counter); + if (ret < ctx->counter) goto error_eof; + offset = ctx->counter; dss_skip_audio_header(s, pkt); - offset = size2; } + ctx->counter -= read_size; ret = avio_read(s->pb, ctx->dss_sp_buf + offset + buff_offset, read_size - offset); @@ -278,7 +276,7 @@ static int dss_723_1_read_packet(AVFormatContext *s, AVPacket *pkt) size = frame_size[byte & 3]; ctx->packet_size = size; - ctx->counter -= size; + ctx->counter--; ret = av_new_packet(pkt, size); if (ret < 0) @@ -288,27 +286,26 @@ static int dss_723_1_read_packet(AVFormatContext *s, AVPacket *pkt) pkt->data[0] = byte; offset = 1; pkt->duration = 240; - s->bit_rate = 8LL * size * st->codecpar->sample_rate * 512 / (506 * pkt->duration); + s->bit_rate = 8LL * size-- * st->codecpar->sample_rate * 512 / (506 * pkt->duration); pkt->stream_index = 0; - if (ctx->counter < 0) { - int size2 = ctx->counter + size; - + if (ctx->counter < size) { ret = avio_read(s->pb, pkt->data + offset, - size2 - offset); - if (ret < size2 - offset) { + ctx->counter); + if (ret < ctx->counter) return ret < 0 ? ret : AVERROR_EOF; - } + offset += ctx->counter; + size -= ctx->counter; + ctx->counter = 0; dss_skip_audio_header(s, pkt); - offset = size2; } + ctx->counter -= size; - ret = avio_read(s->pb, pkt->data + offset, size - offset); - if (ret < size - offset) { + ret = avio_read(s->pb, pkt->data + offset, size); + if (ret < size) return ret < 0 ? ret : AVERROR_EOF; - } return pkt->size; }