Use fdsan on Android.

When available, use ScopedGeneric's ownership tracking to guard its
file descriptors with fdsan.

Bug: 882733
Change-Id: Ibe600465d6bb7e3032e23ed813dea3d8f8ededa8
Reviewed-on: https://chromium-review.googlesource.com/c/1225309
Commit-Queue: Josh Gao <jmgao@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604083}

base/BUILD.gn

@@ -303,6 +303,7 @@ jumbo_component("base") {
     "files/platform_file.h",
     "files/scoped_file.cc",
     "files/scoped_file.h",
+    "files/scoped_file_android.cc",
     "files/scoped_temp_dir.cc",
     "files/scoped_temp_dir.h",
     "format_macros.h",

base/files/scoped_file.h

@@ -18,7 +18,15 @@ namespace base {
 
 namespace internal {
 
-#if defined(OS_POSIX) || defined(OS_FUCHSIA)
+#if defined(OS_ANDROID)
+// Use fdsan on android.
+struct BASE_EXPORT ScopedFDCloseTraits : public ScopedGenericOwnershipTracking {
+  static int InvalidValue() { return -1; }
+  static void Free(int);
+  static void Acquire(const ScopedGeneric<int, ScopedFDCloseTraits>&, int);
+  static void Release(const ScopedGeneric<int, ScopedFDCloseTraits>&, int);
+};
+#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
 struct BASE_EXPORT ScopedFDCloseTraits {
   static int InvalidValue() {
     return -1;

base/files/scoped_file_android.cc

+// Copyright 2018 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 "base/files/scoped_file.h"
+
+#include <stdint.h>
+
+// Copied from <android/fdsan.h>.
+// This can go away once this header is included in our copy of the NDK.
+extern "C" {
+void android_fdsan_exchange_owner_tag(int fd,
+                                      uint64_t expected_tag,
+                                      uint64_t new_tag)
+    __attribute__((__weak__));
+}
+
+namespace base {
+namespace internal {
+
+static uint64_t ScopedFDToTag(const ScopedFD& owner) {
+  return reinterpret_cast<uint64_t>(&owner);
+}
+
+// static
+void ScopedFDCloseTraits::Acquire(const ScopedFD& owner, int fd) {
+  if (android_fdsan_exchange_owner_tag) {
+    android_fdsan_exchange_owner_tag(fd, 0, ScopedFDToTag(owner));
+  }
+}
+
+// static
+void ScopedFDCloseTraits::Release(const ScopedFD& owner, int fd) {
+  if (android_fdsan_exchange_owner_tag) {
+    android_fdsan_exchange_owner_tag(fd, ScopedFDToTag(owner), 0);
+  }
+}
+
+}  // namespace internal
+}  // namespace base