avcodec/huffyuvdec: Check input buffer size

Fixes: Timeout
Fixes: 5487/clusterfuzz-testcase-4696837035393024

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

libavcodec/huffyuvdec.c

@@ -919,6 +919,9 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
     AVFrame *const p = data;
     int table_size = 0, ret;
 
+    if (buf_size < (width * height + 7)/8)
+        return AVERROR_INVALIDDATA;
+
     av_fast_padded_malloc(&s->bitstream_buffer,
                    &s->bitstream_buffer_size,
                    buf_size);