avcodec/hdrdec: Check input size before buffer allocation

Fixes: Timeout
Fixes: 471948155/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HDR_DEC_fuzzer-5679690418552832

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

libavcodec/hdrdec.c

@@ -126,6 +126,9 @@ static int hdr_decode_frame(AVCodecContext *avctx, AVFrame *p,
         ;
     }
 
+    if (bytestream2_get_bytes_left(&gb) < height * 4)
+        return AVERROR_INVALIDDATA;
+
     if ((ret = ff_set_dimensions(avctx, width, height)) < 0)
         return ret;