Bug 1534780 - Add free interconversion between UniqueFileHandle and ipc::FileDescriptor and use it in a few places. r=froydnj

Now that UniqueFileHandle can be used more widely, and with
ipc::FileDescriptor being essentially a copyable UniqueFileHandle, it
makes sense to add a move constructor and a "forget"-like method to
convert between them when needed.

Depends on D26737

Differential Revision: https://phabricator.services.mozilla.com/D26738

--HG--
extra : moz-landing-system : lando

ipc/glue/FileDescriptor.cpp

@@ -31,6 +31,9 @@ FileDescriptor::FileDescriptor(FileDescriptor&& aOther)
 FileDescriptor::FileDescriptor(PlatformHandleType aHandle)
     : mHandle(Clone(aHandle)) {}
 
+FileDescriptor::FileDescriptor(UniquePlatformHandle&& aHandle)
+    : mHandle(std::move(aHandle)) {}
+
 FileDescriptor::FileDescriptor(const IPDLPrivate&, const PickleType& aPickle) {
 #ifdef XP_WIN
   mHandle.reset(aPickle);
@@ -89,6 +92,10 @@ FileDescriptor::UniquePlatformHandle FileDescriptor::ClonePlatformHandle()
   return Clone(mHandle.get());
 }
 
+FileDescriptor::UniquePlatformHandle FileDescriptor::TakePlatformHandle() {
+  return UniquePlatformHandle(mHandle.release());
+}
+
 bool FileDescriptor::operator==(const FileDescriptor& aOther) const {
   return mHandle == aOther.mHandle;
 }

ipc/glue/FileDescriptor.h

@@ -60,6 +60,8 @@ class FileDescriptor {
   // The caller still have to close aHandle.
   explicit FileDescriptor(PlatformHandleType aHandle);
 
+  explicit FileDescriptor(UniquePlatformHandle&& aHandle);
+
   // This constructor WILL NOT duplicate the handle.
   // FileDescriptor takes the ownership from IPC message.
   FileDescriptor(const IPDLPrivate&, const PickleType& aPickle);
@@ -83,6 +85,10 @@ class FileDescriptor {
   // handle.
   UniquePlatformHandle ClonePlatformHandle() const;
 
+  // Extracts the underlying handle and makes this object an invalid handle.
+  // (Compare UniquePtr::release.)
+  UniquePlatformHandle TakePlatformHandle();
+
   // Only used in nsTArray.
   bool operator==(const FileDescriptor& aOther) const;
 

ipc/glue/ProcessUtils_common.cpp

@@ -8,6 +8,7 @@
 
 #include "mozilla/Preferences.h"
 #include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "mozilla/UniquePtrExtensions.h"
 
 namespace mozilla {
 namespace ipc {
@@ -133,16 +134,13 @@ bool SharedPreferenceDeserializer::DeserializeFromSharedMemory(
     return false;
   }
 
-  // The FileDescriptor constructor will clone this handle when constructed,
-  // so store it in a UniquePlatformHandle to make sure the original gets
-  // closed.
   FileDescriptor::UniquePlatformHandle handle(
       parseHandleArg(aPrefMapHandleStr));
   if (!aPrefMapHandleStr || aPrefMapHandleStr[0] != '\0') {
     return false;
   }
 
-  mPrefMapHandle.emplace(handle.get());
+  mPrefMapHandle.emplace(std::move(handle));
 #endif
 
   mPrefsLen = Some(parseUIntPtrArg(aPrefsLenStr));
@@ -160,17 +158,12 @@ bool SharedPreferenceDeserializer::DeserializeFromSharedMemory(
   MOZ_RELEASE_ASSERT(gPrefsFd != -1);
   mPrefsHandle = Some(base::FileDescriptor(gPrefsFd, /* auto_close */ true));
 
-  FileDescriptor::UniquePlatformHandle handle(gPrefMapFd);
-  mPrefMapHandle.emplace(handle.get());
+  mPrefMapHandle.emplace(UniqueFileHandle(gPrefMapFd));
 #elif XP_UNIX
   mPrefsHandle = Some(base::FileDescriptor(kPrefsFileDescriptor,
                                            /* auto_close */ true));
 
-  // The FileDescriptor constructor will clone this handle when constructed,
-  // so store it in a UniquePlatformHandle to make sure the original gets
-  // closed.
-  FileDescriptor::UniquePlatformHandle handle(kPrefMapFileDescriptor);
-  mPrefMapHandle.emplace(handle.get());
+  mPrefMapHandle.emplace(UniqueFileHandle(kPrefMapFileDescriptor));
 #endif
 
   if (mPrefsHandle.isNothing() || mPrefsLen.isNothing() ||

security/sandbox/linux/gtest/TestBroker.cpp

@@ -87,7 +87,7 @@ class SandboxBrokerTest : public ::testing::Test {
     mServer = SandboxBroker::Create(GetPolicy(), getpid(), fd);
     ASSERT_NE(mServer, nullptr);
     ASSERT_TRUE(fd.IsValid());
-    auto rawFD = fd.ClonePlatformHandle();
+    auto rawFD = fd.TakePlatformHandle();
     mClient.reset(new SandboxBrokerClient(rawFD.release()));
   }