[llvm] Windows: use EcoQoS for ThreadPriority::Background (PR #148797)

[Alexandre Ganea via llvm-commits]

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@@ -106,7 +106,66 @@ void llvm::get_thread_name(SmallVectorImpl<char> &Name) {
   Name.clear();
 }
 
+static HMODULE LoadSystemModuleSecure(LPCWSTR lpModuleName) {
+  // Ensure we load indeed a module from system32 path.
+  // As per GetModuleHandle documentation:
+  // "If lpModuleName does not include a path and there is more than one loaded
+  // module with the same base name and extension, you cannot predict which
+  // module handle will be returned.". This mitigates
+  // https://learn.microsoft.com/en-us/security-updates/securityadvisories/2010/2269637
+  SmallVector<wchar_t, MAX_PATH> Buf;
+  size_t Size = MAX_PATH;
+  do {
+    Buf.resize_for_overwrite(Size);
+    SetLastError(NO_ERROR);
+    Size = ::GetSystemDirectoryW(Buf.data(), Buf.size());
+    if (Size == 0)
+      return NULL;
+
+    // Try again with larger buffer.
+  } while (Size > Buf.size());
+
+  Buf.truncate(Size);
+  Buf.push_back(TEXT('\\'));
+  Buf.append(lpModuleName, lpModuleName + std::wcslen(lpModuleName));
+  Buf.push_back(0);
+
+  return ::GetModuleHandleW(Buf.data());
+}
+
 SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) {
+  HMODULE kernelMod = LoadSystemModuleSecure(TEXT("kernel32.dll"));
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aganea wrote:

As suggested.

https://github.com/llvm/llvm-project/pull/148797