sonic: make sure num_taps * channels is not larger than frame_size

If that is the case, the loop setting predictor_state in
sonic_decode_frame causes out of bounds reads of int_samples, which has
only frame_size number of elements.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavcodec/sonic.c

@@ -928,6 +928,13 @@ static av_cold int sonic_decode_init(AVCodecContext *avctx)
     s->frame_size = s->channels*s->block_align*s->downsampling;
 //    avctx->frame_size = s->block_align;
 
+    if (s->num_taps * s->channels > s->frame_size) {
+        av_log(avctx, AV_LOG_ERROR,
+               "number of taps times channels (%d * %d) larger than frame size %d\n",
+               s->num_taps, s->channels, s->frame_size);
+        return AVERROR_INVALIDDATA;
+    }
+
     av_log(avctx, AV_LOG_INFO, "Sonic: ver: %d.%d ls: %d dr: %d taps: %d block: %d frame: %d downsamp: %d\n",
         s->version, s->minor_version, s->lossless, s->decorrelation, s->num_taps, s->block_align, s->frame_size, s->downsampling);