ffmpeg | branch: master | Derek Buitenhuis <derek.buitenh...@gmail.com> | Thu Apr 20 15:02:54 2017 +0100| [8e6b9ef4733be91b32c8b7becd95124340b92334] | committer: Derek Buitenhuis
webm_dash_manifest_demuxer: Fix UB in cue timestamp string code and make it actually work Output was apparently not tested for correctness. Passing overlapping memory to snprintf causes undefined behavior, and usually resulted in only the very last timestamp being written to metadata, and not a list at all. Signed-off-by: Derek Buitenhuis <derek.buitenh...@gmail.com> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=8e6b9ef4733be91b32c8b7becd95124340b92334 --- libavformat/matroskadec.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c index 9adca8dcc0..320d8bfeac 100644 --- a/libavformat/matroskadec.c +++ b/libavformat/matroskadec.c @@ -3823,6 +3823,7 @@ static int webm_dash_manifest_cues(AVFormatContext *s) char *buf; int64_t cues_start = -1, cues_end = -1, before_pos, bandwidth; int i; + int end = 0; // determine cues start and end positions for (i = 0; i < seekhead_list->nb_elem; i++) @@ -3868,10 +3869,17 @@ static int webm_dash_manifest_cues(AVFormatContext *s) if (!buf) return -1; strcpy(buf, ""); for (i = 0; i < s->streams[0]->nb_index_entries; i++) { - snprintf(buf, (i + 1) * 20 * sizeof(char), - "%s%" PRId64, buf, s->streams[0]->index_entries[i].timestamp); - if (i != s->streams[0]->nb_index_entries - 1) + int ret = snprintf(buf + end, 20 * sizeof(char), + "%" PRId64, s->streams[0]->index_entries[i].timestamp); + if (ret <= 0 || (ret == 20 && i == s->streams[0]->nb_index_entries - 1)) { + av_log(s, AV_LOG_ERROR, "timestamp too long.\n"); + return AVERROR_INVALIDDATA; + } + end += ret; + if (i != s->streams[0]->nb_index_entries - 1) { strncat(buf, ",", sizeof(char)); + end++; + } } av_dict_set(&s->streams[0]->metadata, CUE_TIMESTAMPS, buf, 0); av_free(buf); _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog
