avcodec/hevc_mp4toannexb: more validations for nalu_len

For a corrupted stream, the value of nalu_len read from the extradata is not reliable.
We need to perform additional checks

libavcodec/bsf/hevc_mp4toannexb.c

@@ -65,9 +65,11 @@ static int hevc_extradata_to_annexb(AVBSFContext *ctx)
         }
 
         for (j = 0; j < cnt; j++) {
-            int nalu_len = bytestream2_get_be16(&gb);
+            const int nalu_len = bytestream2_get_be16(&gb);
 
-            if (4 + AV_INPUT_BUFFER_PADDING_SIZE + nalu_len > SIZE_MAX - new_extradata_size) {
+            if (!nalu_len ||
+                nalu_len > bytestream2_get_bytes_left(&gb) ||
+                4 + AV_INPUT_BUFFER_PADDING_SIZE + nalu_len > SIZE_MAX - new_extradata_size) {
                 ret = AVERROR_INVALIDDATA;
                 goto fail;
             }