Revert "Revert "base: add support for tagged fd closure to unique_fd.""

Use __attribute__((weak)) to check for fdsan availability at runtime,
to support being used when built with the NDK while targeting older
platform versions.

This reverts commit af798acaea49b8d9150b94eb9f5f11450a6b8893.

Bug: http://b/110100358
Test: m libjnitest
Change-Id: Ie59d041d69cc3d4b6c59412d706f702dd1d2dab2

base/Android.bp

@@ -135,6 +135,7 @@ cc_test {
         "strings_test.cpp",
         "test_main.cpp",
         "test_utils_test.cpp",
+        "unique_fd_test.cpp",
     ],
     target: {
         android: {

base/include/android-base/unique_fd.h

@@ -42,10 +42,35 @@
 //
 // unique_fd is also known as ScopedFd/ScopedFD/scoped_fd; mentioned here to help
 // you find this class if you're searching for one of those names.
+
+#if defined(__BIONIC__)
+#include <android/fdsan.h>
+#endif
+
 namespace android {
 namespace base {
 
 struct DefaultCloser {
+#if defined(__BIONIC__)
+  static void Tag(int fd, void* old_addr, void* new_addr) {
+    if (android_fdsan_exchange_owner_tag) {
+      uint64_t old_tag = android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_UNIQUE_FD,
+                                                        reinterpret_cast<uint64_t>(old_addr));
+      uint64_t new_tag = android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_UNIQUE_FD,
+                                                        reinterpret_cast<uint64_t>(new_addr));
+      android_fdsan_exchange_owner_tag(fd, old_tag, new_tag);
+    }
+  }
+  static void Close(int fd, void* addr) {
+    if (android_fdsan_close_with_tag) {
+      uint64_t tag = android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_UNIQUE_FD,
+                                                    reinterpret_cast<uint64_t>(addr));
+      android_fdsan_close_with_tag(fd, tag);
+    } else {
+      close(fd);
+    }
+  }
+#else
   static void Close(int fd) {
     // Even if close(2) fails with EINTR, the fd will have been closed.
     // Using TEMP_FAILURE_RETRY will either lead to EBADF or closing someone
@@ -53,40 +78,75 @@ struct DefaultCloser {
     // http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
     ::close(fd);
   }
+#endif
 };
 
 template <typename Closer>
 class unique_fd_impl final {
  public:
-  unique_fd_impl() : value_(-1) {}
+  unique_fd_impl() {}
 
-  explicit unique_fd_impl(int value) : value_(value) {}
+  explicit unique_fd_impl(int fd) { reset(fd); }
   ~unique_fd_impl() { reset(); }
 
-  unique_fd_impl(unique_fd_impl&& other) : value_(other.release()) {}
+  unique_fd_impl(unique_fd_impl&& other) { reset(other.release()); }
   unique_fd_impl& operator=(unique_fd_impl&& s) {
-    reset(s.release());
+    int fd = s.fd_;
+    s.fd_ = -1;
+    reset(fd, &s);
     return *this;
   }
 
-  void reset(int new_value = -1) {
-    if (value_ != -1) {
-      Closer::Close(value_);
-    }
-    value_ = new_value;
-  }
+  void reset(int new_value = -1) { reset(new_value, nullptr); }
 
-  int get() const { return value_; }
+  int get() const { return fd_; }
   operator int() const { return get(); }
 
   int release() __attribute__((warn_unused_result)) {
-    int ret = value_;
-    value_ = -1;
+    tag(fd_, this, nullptr);
+    int ret = fd_;
+    fd_ = -1;
     return ret;
   }
 
  private:
-  int value_;
+  void reset(int new_value, void* previous_tag) {
+    if (fd_ != -1) {
+      close(fd_, this);
+    }
+
+    fd_ = new_value;
+    if (new_value != -1) {
+      tag(new_value, previous_tag, this);
+    }
+  }
+
+  int fd_ = -1;
+
+  // Template magic to use Closer::Tag if available, and do nothing if not.
+  // If Closer::Tag exists, this implementation is preferred, because int is a better match.
+  // If not, this implementation is SFINAEd away, and the no-op below is the only one that exists.
+  template <typename T = Closer>
+  static auto tag(int fd, void* old_tag, void* new_tag)
+      -> decltype(T::Tag(fd, old_tag, new_tag), void()) {
+    T::Tag(fd, old_tag, new_tag);
+  }
+
+  template <typename T = Closer>
+  static void tag(long, void*, void*) {
+    // No-op.
+  }
+
+  // Same as above, to select between Closer::Close(int) and Closer::Close(int, void*).
+  template <typename T = Closer>
+  static auto close(int fd, void* tag_value) -> decltype(T::Close(fd, tag_value), void()) {
+    T::Close(fd, tag_value);
+  }
+
+  template <typename T = Closer>
+  static auto close(int fd, void*) -> decltype(T::Close(fd), void()) {
+    T::Close(fd);
+  }
 
   unique_fd_impl(const unique_fd_impl&);
   void operator=(const unique_fd_impl&);

base/unique_fd_test.cpp

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "android-base/unique_fd.h"
+
+#include <gtest/gtest.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+using android::base::unique_fd;
+
+TEST(unique_fd, unowned_close) {
+#if defined(__BIONIC__)
+  unique_fd fd(open("/dev/null", O_RDONLY));
+  EXPECT_DEATH(close(fd.get()), "incorrect tag");
+#endif
+}
+
+TEST(unique_fd, untag_on_release) {
+  unique_fd fd(open("/dev/null", O_RDONLY));
+  close(fd.release());
+}
+
+TEST(unique_fd, move) {
+  unique_fd fd(open("/dev/null", O_RDONLY));
+  unique_fd fd_moved = std::move(fd);
+  ASSERT_EQ(-1, fd.get());
+  ASSERT_GT(fd_moved.get(), -1);
+}
+
+TEST(unique_fd, unowned_close_after_move) {
+#if defined(__BIONIC__)
+  unique_fd fd(open("/dev/null", O_RDONLY));
+  unique_fd fd_moved = std::move(fd);
+  ASSERT_EQ(-1, fd.get());
+  ASSERT_GT(fd_moved.get(), -1);
+  EXPECT_DEATH(close(fd_moved.get()), "incorrect tag");
+#endif
+}