From 71a9e9b3cb98348c77fe370eb5643faf47613c61 Mon Sep 17 00:00:00 2001
From: Kirk Steuber <ksteuber@mozilla.com>
Date: Wed, 8 Dec 2021 19:13:01 +0000
Subject: [PATCH] Bug 1732435 - r=nalexander

Differential Revision: https://phabricator.services.mozilla.com/D127897
---
 toolkit/xre/MultiInstanceLock.cpp | 80 +++++++++++++++++++++++--------
 1 file changed, 61 insertions(+), 19 deletions(-)

diff --git a/toolkit/xre/MultiInstanceLock.cpp b/toolkit/xre/MultiInstanceLock.cpp
index a04cca08bd3c..9dfacd0cff6d 100644
--- a/toolkit/xre/MultiInstanceLock.cpp
+++ b/toolkit/xre/MultiInstanceLock.cpp
@@ -12,7 +12,9 @@
 #include "nsPromiseFlatString.h"
 #include "updatedefines.h"  // for NS_t* definitions
 
-#ifndef XP_WIN
+#ifdef XP_WIN
+#  include <shlwapi.h>
+#else
 #  include <fcntl.h>
 #  include <sys/stat.h>
 #  include <sys/types.h>
@@ -22,29 +24,69 @@ namespace mozilla {
 
 static bool GetLockFileName(const char* nameToken, const char16_t* installPath,
                             nsCString& filePath) {
+#ifdef XP_WIN
+  // On Windows, the lock file is placed at the path
+  // [updateDirectory]\[nameToken]-[pathHash], so first we need to get the
+  // update directory path and then append the file name.
+
+  // Note: This will return something like
+  //   C:\ProgramData\Mozilla-1de4eec8-1241-4177-a864-e594e8d1fb38\updates\<hash>
+  // But we actually are going to want to return the root update directory,
+  // the grandparent of this directory, which will look something like this:
+  //   C:\ProgramData\Mozilla-1de4eec8-1241-4177-a864-e594e8d1fb38
+  mozilla::UniquePtr<wchar_t[]> updateDir;
+  HRESULT hr = GetCommonUpdateDirectory(
+      reinterpret_cast<const wchar_t*>(installPath), updateDir);
+  if (FAILED(hr)) {
+    return false;
+  }
+
+  // For the path manipulation that we are about to do, it is important that
+  // the update directory have no trailing slash.
+  size_t len = wcslen(updateDir.get());
+  if (len == 0) {
+    return false;
+  }
+  if (updateDir.get()[len - 1] == '/' || updateDir.get()[len - 1] == '\\') {
+    updateDir.get()[len - 1] = '\0';
+  }
+
+  wchar_t* hashPtr = PathFindFileNameW(updateDir.get());
+  // PathFindFileNameW returns a pointer to the beginning of the string on
+  // failure.
+  if (hashPtr == updateDir.get()) {
+    return false;
+  }
+
+  // We need to make a copy of the hash before we modify updateDir to get the
+  // root update dir.
+  size_t hashSize = wcslen(hashPtr) + 1;
+  mozilla::UniquePtr<wchar_t[]> hash = mozilla::MakeUnique<wchar_t[]>(hashSize);
+  errno_t error = wcscpy_s(hash.get(), hashSize, hashPtr);
+  if (error != 0) {
+    return false;
+  }
+
+  // Get the root update dir from the update dir.
+  BOOL success = PathRemoveFileSpecW(updateDir.get());
+  if (!success) {
+    return false;
+  }
+  success = PathRemoveFileSpecW(updateDir.get());
+  if (!success) {
+    return false;
+  }
+
+  filePath =
+      nsPrintfCString("%s\\%s-%s", NS_ConvertUTF16toUTF8(updateDir.get()).get(),
+                      nameToken, NS_ConvertUTF16toUTF8(hash.get()).get());
+
+#else
   mozilla::UniquePtr<NS_tchar[]> pathHash;
   if (!GetInstallHash(installPath, pathHash)) {
     return false;
   }
 
-#ifdef XP_WIN
-  // On Windows, the lock file is placed at the path
-  // ProgramData\[vendor]\[nameToken]-[pathHash], so first we need to get the
-  // ProgramData path and then append our directory and the file name.
-  PWSTR programDataPath;
-  HRESULT hr = SHGetKnownFolderPath(FOLDERID_ProgramData, KF_FLAG_CREATE,
-                                    nullptr, &programDataPath);
-  if (FAILED(hr)) {
-    return false;
-  }
-  mozilla::UniquePtr<wchar_t, CoTaskMemFreeDeleter> programDataPathUnique(
-      programDataPath);
-
-  filePath = nsPrintfCString(
-      "%s\\%s\\%s-%s", NS_ConvertUTF16toUTF8(programDataPath).get(),
-      MOZ_APP_VENDOR, nameToken, NS_ConvertUTF16toUTF8(pathHash.get()).get());
-
-#else
   // On POSIX platforms the base path is /tmp/[vendor][nameToken]-[pathHash].
   filePath = nsPrintfCString("/tmp/%s%s-%s", MOZ_APP_VENDOR, nameToken,
                              pathHash.get());