avcodec/wavarc: Allocate AV_INPUT_BUFFER_PADDING_SIZE

Fixes: overread
Fixes: 62164/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WAVARC_fuzzer-5963163952349184
Fixes: 62164/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WAVARC_fuzzer-6048030137909248

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit dbcf285abd)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/wavarc.c

@@ -98,7 +98,7 @@ static av_cold int wavarc_init(AVCodecContext *avctx)
     }
 
     s->max_framesize = s->nb_samples * 16;
-    s->bitstream = av_calloc(s->max_framesize, sizeof(*s->bitstream));
+    s->bitstream = av_calloc(s->max_framesize + AV_INPUT_BUFFER_PADDING_SIZE, sizeof(*s->bitstream));
     if (!s->bitstream)
         return AVERROR(ENOMEM);