[FFmpeg-cvslog] alac: Check that the channels fit at the given offset

[Martin Storsjö]

ffmpeg | branch: master | Martin Storsjö <martin at martin.st> | Tue Sep  3 14:16:40 2013 +0300| [35cbc98b720db95b923cb2d745f77bb2ee4363dc] | committer: Martin Storsjö

alac: Check that the channels fit at the given offset

The code tries to decode a number of channels at the
offset given by the ff_alac_channel_layout_offsets table.
Even if the number of channels decoded so far doesn't
exceed the total number of channels, we need to check that
we actually can decode that number of channels at this offset
as well.

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable at libav.org
Signed-off-by: Martin Storsjö <martin at martin.st>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=35cbc98b720db95b923cb2d745f77bb2ee4363dc
---

 libavcodec/alac.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/alac.c b/libavcodec/alac.c
index d643dd3..41d1f77 100644
--- a/libavcodec/alac.c
+++ b/libavcodec/alac.c
@@ -418,7 +418,8 @@ static int alac_decode_frame(AVCodecContext *avctx, void *data,
         }
 
         channels = (element == TYPE_CPE) ? 2 : 1;
-        if (ch + channels > alac->channels) {
+        if (ch + channels > alac->channels ||
+            ff_alac_channel_layout_offsets[alac->channels - 1][ch] + channels > alac->channels) {
             av_log(avctx, AV_LOG_ERROR, "invalid element channel count\n");
             return AVERROR_INVALIDDATA;
         }