From c49dfee90bc1c149410f7017e9cbbbeb4063ccdf Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Sun, 14 Jun 2020 03:35:41 +0200 Subject: [PATCH] avformat/matroskaenc: Don't use NULL for %s format string The argument pertaining to a printf %s conversion specifier must not be NULL, even if the precision (i.e. the number of characters to write) is zero. If it is NULL, it is undefined behaviour. Signed-off-by: Andreas Rheinhardt (cherry picked from commit 6de6ce7bc80e874099895b6c73977bc2efb06a4d) --- libavformat/matroskaenc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c index 1c1ea71f59..eaed02bc92 100644 --- a/libavformat/matroskaenc.c +++ b/libavformat/matroskaenc.c @@ -2118,17 +2118,19 @@ static int mkv_write_vtt_blocks(AVFormatContext *s, AVIOContext *pb, const AVPac mkv_track *track = &mkv->tracks[pkt->stream_index]; ebml_master blockgroup; int id_size, settings_size, size; - uint8_t *id, *settings; + const char *id, *settings; int64_t ts = track->write_dts ? pkt->dts : pkt->pts; const int flags = 0; id_size = 0; id = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_IDENTIFIER, &id_size); + id = id ? id : ""; settings_size = 0; settings = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_SETTINGS, &settings_size); + settings = settings ? settings : ""; size = id_size + 1 + settings_size + 1 + pkt->size;