avcodec/wavarc: Check order before using it to write the list

Fixes: out of array access
Fixes: 45982/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WAVARC_fuzzer-6247711015043072
Fixes: 45982/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WAVARC_fuzzer-6487578428964864
Fixes: 45982/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WAVARC_fuzzer-6651587794960384
Fixes: 45982/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WAVARC_fuzzer-6686265824378880

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/wavarc.c

@@ -343,6 +343,8 @@ static int decode_2slp(AVCodecContext *avctx,
             break;
         case 0:
             order = get_urice(gb, 2);
+            if ((unsigned)order >= FF_ARRAY_ELEMS(s->filter[ch]))
+                return AVERROR_INVALIDDATA;
             for (int o = 0; o < order; o++)
                 s->filter[ch][o] = get_srice(gb, 2);
             for (int n = 0; n < s->nb_samples; n++) {