[FFmpeg-cvslog] vorbisdec: reject channel mapping with less than two channels

[Andreas Cadhalpun]

ffmpeg | branch: release/2.4 | Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com> | Sun Jan  3 19:20:54 2016 +0100| [7b6f04850610cbf6ef3a282423a89098ae02a57e] | committer: Andreas Cadhalpun

vorbisdec: reject channel mapping with less than two channels

It causes the angle channel number to equal the magnitude channel
number, which makes the stream undecodable according to the
specification.

Reviewed-by: Michael Niedermayer <michael at niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
(cherry picked from commit b4b13848dec5420fa5dd9e1a7d4dfae5de1932d5)
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=7b6f04850610cbf6ef3a282423a89098ae02a57e
---

 libavcodec/vorbisdec.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/vorbisdec.c b/libavcodec/vorbisdec.c
index 984b658..e28972c 100644
--- a/libavcodec/vorbisdec.c
+++ b/libavcodec/vorbisdec.c
@@ -783,6 +783,11 @@ static int vorbis_parse_setup_hdr_mappings(vorbis_context *vc)
 
         if (get_bits1(gb)) {
             mapping_setup->coupling_steps = get_bits(gb, 8) + 1;
+            if (vc->audio_channels < 2) {
+                av_log(vc->avctx, AV_LOG_ERROR,
+                       "Square polar channel mapping with less than two channels is not compliant with the Vorbis I specification.\n");
+                return AVERROR_INVALIDDATA;
+            }
             mapping_setup->magnitude      = av_mallocz(mapping_setup->coupling_steps *
                                                        sizeof(*mapping_setup->magnitude));
             mapping_setup->angle          = av_mallocz(mapping_setup->coupling_steps *