avcodec/wmaprodec: Check if the channel sum of all internal contexts match the external

Fixes: NULL pointer dereference
Fixes: 18689/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_XMA1_fuzzer-5715114640015360
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/wmaprodec.c b/libavcodec/wmaprodec.c
index 87e2ead693fb081b2fbf454b98411550434554cb..6a22e2f552ee0dbee08b2460a73630b5107008e4 100644 (file)
--- a/libavcodec/wmaprodec.c
+++ b/libavcodec/wmaprodec.c
@@ -1930,6 +1930,8 @@ static av_cold int xma_decode_init(AVCodecContext *avctx)
         s->start_channel[i] = start_channels;
         start_channels += s->xma[i].nb_channels;
     }
+    if (start_channels != avctx->channels)
+        return AVERROR_INVALIDDATA;
 
     return ret;
 }