Bug 1603998 - Close leaking FDs of the fork server. r=gsvelto

* Close leaking FDs of the fork server.
* Init the fork server before the initialization of the leak checker  to avoid log files from taking lower file descriptor numbers.

Differential Revision: https://phabricator.services.mozilla.com/D57216

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

ipc/chromium/src/base/process_util_linux.cc

@@ -24,6 +24,9 @@
 #include "mozilla/DebugOnly.h"
 #include "mozilla/ipc/ForkServiceChild.h"
 
+#include "mozilla/Unused.h"
+#include "mozilla/ScopeExit.h"
+
 using namespace mozilla::ipc;
 #endif
 
@@ -78,6 +81,13 @@ ReplaceEnviroment(const LaunchOptions& options) {
 bool
 AppProcessBuilder::ForkProcess(const std::vector<std::string>& argv,
                                const LaunchOptions& options, ProcessHandle* process_handle) {
+  auto cleanFDs = mozilla::MakeScopeExit([&] {
+    for (auto& elt : options.fds_to_remap) {
+      auto fd = std::get<0>(elt);
+      close(fd);
+    }
+  });
+
   argv_ = argv;
   if (!shuffle_.Init(options.fds_to_remap)) {
     return false;
@@ -104,6 +114,7 @@ AppProcessBuilder::ForkProcess(const std::vector<std::string>& argv,
   }
 
   if (pid == 0) {
+    cleanFDs.release();
     ReplaceEnviroment(options);
   } else {
     gProcessLog.print("==> process %d launched child process %d\n",
@@ -178,7 +189,7 @@ ReserveFileDescriptors() {
   // out any confliction with mapping passing from the parent process.
   int fd = open("/dev/null", O_RDONLY);
   for (int i = 1; i < 10; i++) {
-    dup(fd);
+    mozilla::Unused << dup(fd);
   }
 }
 

ipc/glue/ForkServer.cpp

@@ -262,14 +262,16 @@ ForkServer::RunForkServer(int* aArgc, char*** aArgv) {
     bool sleep_newproc = !!getenv("MOZ_FORKSERVER_WAIT_GDB_NEWPROC");
 #endif
 
+    // Do this before NS_LogInit() to avoid log files taking lower
+    // FDs.
+    ForkServer forkserver;
+    forkserver.InitProcess(aArgc, aArgv);
+
     XRE_SetProcessType("forkserver");
     NS_LogInit();
     mozilla::LogModule::Init(0, nullptr);
     MOZ_LOG(gForkServiceLog, LogLevel::Verbose, ("Start a fork server"));
-    ForkServer forkserver;
     {
-        forkserver.InitProcess(aArgc, aArgv);
-
         DebugOnly<base::ProcessHandle> forkserver_pid = base::GetCurrentProcId();
         if (forkserver.HandleMessages()) {
             // In the fork server process

ipc/glue/MiniTransceiver.cpp

@@ -8,6 +8,8 @@
 #include "base/eintr_wrapper.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/DebugOnly.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/ScopeExit.h"
 #include "nsDebug.h"
 
 #include <sys/types.h>
@@ -109,6 +111,10 @@ MiniTransceiver::Send(IPC::Message& aMsg) {
     mState = STATE_SENDING;
 #endif
 
+    auto clean_fdset = MakeScopeExit([&] {
+            aMsg.file_descriptor_set()->CommitAll();
+    });
+
     int num_fds = aMsg.file_descriptor_set()->size();
     msghdr hdr;
     InitMsgHdr(&hdr, kMaxIOVecSize, num_fds);
@@ -122,7 +128,7 @@ MiniTransceiver::Send(IPC::Message& aMsg) {
 
     if (bytes_written < 0) {
         char error[128];
-        snprintf(error, sizeof(error), "sendmsg: %s", strerror(errno));
+        SprintfLiteral(error, "sendmsg: %s", strerror(errno));
         NS_WARNING(error);
         return false;
     }

ipc/glue/MiniTransceiver.h

@@ -37,7 +37,7 @@ public:
      * \param aClearDataBuf is true to clear data buffers after
      *                      receiving a message.
      */
-    MiniTransceiver(int aFd, DataBufferClear aDataBufClear = DataBufferClear::None);
+    explicit MiniTransceiver(int aFd, DataBufferClear aDataBufClear = DataBufferClear::None);
 
     bool Send(IPC::Message& aMsg);
     inline bool SendInfallible(IPC::Message& aMsg, const char* aCrashMessage) {