[Windows] Add checks for DLL loader lock.

This CL adds code to check if the current thread holds the DLL loader
lock. This code can be used to enforce the requirement that certain
parts of crashpad, such as process creation are not done during calls
to DllMain which can lead to deadlocks and crashes. Only one check is
current enforced, in client process creation, and only in debug builds.

Bug: crashpad: 316
Change-Id: I5757a264bbf28ce2ab88a0cd7ac9481e46428c17
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/1945993
Reviewed-by: Mark Mentovai <mark@chromium.org>
Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: James Forshaw <forshaw@chromium.org>

client/crashpad_client_win.cc

@@ -41,6 +41,7 @@
 #include "util/win/get_function.h"
 #include "util/win/handle.h"
 #include "util/win/initial_client_data.h"
+#include "util/win/loader_lock.h"
 #include "util/win/nt_internals.h"
 #include "util/win/ntstatus_logging.h"
 #include "util/win/process_info.h"
@@ -346,6 +347,8 @@ class ScopedCallSetHandlerStartupState {
 
 bool StartHandlerProcess(
     std::unique_ptr<BackgroundHandlerStartThreadData> data) {
+  CHECK(!IsThreadInLoaderLock());
+
   ScopedCallSetHandlerStartupState scoped_startup_state_caller;
 
   std::wstring command_line;

util/BUILD.gn

@@ -371,6 +371,8 @@ static_library("util") {
       "win/handle.h",
       "win/initial_client_data.cc",
       "win/initial_client_data.h",
+      "win/loader_lock.cc",
+      "win/loader_lock.h",
       "win/module_version.cc",
       "win/module_version.h",
       "win/nt_internals.cc",
@@ -666,6 +668,7 @@ source_set("util_test") {
       "win/get_function_test.cc",
       "win/handle_test.cc",
       "win/initial_client_data_test.cc",
+      "win/loader_lock_test.cc",
       "win/process_info_test.cc",
       "win/registration_protocol_win_test.cc",
       "win/safe_terminate_process_test.cc",
@@ -718,6 +721,7 @@ source_set("util_test") {
       "dbghelp.lib",
     ]
     data_deps += [
+      ":crashpad_util_test_loader_lock_test",
       ":crashpad_util_test_process_info_test_child",
       ":crashpad_util_test_safe_terminate_process_test_child",
     ]
@@ -738,4 +742,14 @@ if (crashpad_is_win) {
       "win/safe_terminate_process_test_child.cc",
     ]
   }
+
+  crashpad_loadable_module("crashpad_util_test_loader_lock_test") {
+    testonly = true
+    sources = [
+      "win/loader_lock_test_dll.cc",
+    ]
+    deps = [
+      ":util",
+    ]
+  }
 }

util/win/loader_lock.cc

@@ -0,0 +1,52 @@
+// Copyright 2019 The Crashpad Authors. All rights reserved.
+//
+// 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 "util/win/loader_lock.h"
+
+#include <windows.h>
+
+#include "build/build_config.h"
+#include "util/win/process_structs.h"
+
+namespace crashpad {
+
+namespace {
+
+#ifdef ARCH_CPU_64_BITS
+using NativeTraits = process_types::internal::Traits64;
+#else
+using NativeTraits = process_types::internal::Traits32;
+#endif  // ARCH_CPU_64_BITS
+
+using PEB = process_types::PEB<NativeTraits>;
+using TEB = process_types::TEB<NativeTraits>;
+using RTL_CRITICAL_SECTION = process_types::RTL_CRITICAL_SECTION<NativeTraits>;
+
+TEB* GetTeb() {
+  return reinterpret_cast<TEB*>(NtCurrentTeb());
+}
+
+PEB* GetPeb() {
+  return reinterpret_cast<PEB*>(GetTeb()->ProcessEnvironmentBlock);
+}
+
+}  // namespace
+
+bool IsThreadInLoaderLock() {
+  RTL_CRITICAL_SECTION* loader_lock =
+      reinterpret_cast<RTL_CRITICAL_SECTION*>(GetPeb()->LoaderLock);
+  return loader_lock->OwningThread == GetTeb()->ClientId.UniqueThread;
+}
+
+}  // namespace crashpad

util/win/loader_lock.h

@@ -0,0 +1,25 @@
+// Copyright 2019 The Crashpad Authors. All rights reserved.
+//
+// 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.
+
+#ifndef CRASHPAD_UTIL_WIN_LOADER_LOCK_H_
+#define CRASHPAD_UTIL_WIN_LOADER_LOCK_H_
+
+namespace crashpad {
+
+//! \return `true` if the current thread holds the loader lock.
+bool IsThreadInLoaderLock();
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_WIN_LOADER_LOCK_H_

util/win/loader_lock_test.cc

@@ -0,0 +1,36 @@
+// Copyright 2019 The Crashpad Authors. All rights reserved.
+//
+// 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 "util/win/loader_lock.h"
+
+#include "gtest/gtest.h"
+#include "util/win/get_function.h"
+
+extern "C" bool LoaderLockDetected();
+
+namespace crashpad {
+namespace test {
+namespace {
+
+TEST(LoaderLock, Detected) {
+  EXPECT_FALSE(IsThreadInLoaderLock());
+  auto* loader_lock_detected = GET_FUNCTION_REQUIRED(
+      L"crashpad_util_test_loader_lock_test.dll", LoaderLockDetected);
+  EXPECT_TRUE(loader_lock_detected());
+  EXPECT_FALSE(IsThreadInLoaderLock());
+}
+
+}  // namespace
+}  // namespace test
+}  // namespace crashpad

util/win/loader_lock_test_dll.cc

@@ -0,0 +1,41 @@
+// Copyright 2019 The Crashpad Authors. All rights reserved.
+//
+// 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 <windows.h>
+
+#include "util/win/loader_lock.h"
+
+namespace {
+
+bool g_loader_lock_detected = false;
+
+}  // namespace
+
+extern "C" {
+
+__declspec(dllexport) bool LoaderLockDetected() {
+  return g_loader_lock_detected;
+}
+
+}  // extern "C"
+
+BOOL WINAPI DllMain(HINSTANCE, DWORD reason, LPVOID) {
+  switch (reason) {
+    case DLL_PROCESS_ATTACH:
+      g_loader_lock_detected = crashpad::IsThreadInLoaderLock();
+      break;
+  }
+
+  return TRUE;
+}