port libxml_xml_read_memory_fuzzer (from kcc's libfuzzer-bot) and disable...

port libxml_xml_read_memory_fuzzer (from kcc's libfuzzer-bot) and disable error messages from the parser

R=aizatsky@chromium.org, inferno@chromium.org,kcc@chromium.org
TBR=krasin@chromium.org
BUG=569578

Review URL: https://codereview.chromium.org/1558483003

Cr-Commit-Position: refs/heads/master@{#367154}

testing/libfuzzer/fuzzers/BUILD.gn

@@ -255,3 +255,12 @@ fuzzer_test("sqlite3_prepare_v2_fuzzer") {
     "//third_party/sqlite",
   ]
 }
+
+fuzzer_test("libxml_xml_read_memory_fuzzer") {
+  sources = [
+    "libxml_xml_read_memory_fuzzer.cc",
+  ]
+  deps = [
+    "//third_party/libxml:libxml",
+  ]
+}

testing/libfuzzer/fuzzers/libxml_xml_read_memory_fuzzer.cc

+// Copyright (c) 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "libxml/parser.h"
+
+void ignore (void * ctx, const char * msg, ...) {
+  // Error handler to avoid spam of error messages from libxml parser.
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const unsigned char *data, size_t size) {
+  xmlSetGenericErrorFunc(NULL, &ignore);
+
+  if (auto doc = xmlReadMemory(reinterpret_cast<const char *>(data),
+                               size, "noname.xml", NULL, 0)) {
+    xmlFreeDoc(doc);
+  }
+
+  return 0;
+}