From 164363e186c5424650f9ed63b3c21a891da5a971 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?M=C3=A5rten=20Nordheim?= <marten.nordheim@qt.io>
Date: Wed, 10 Apr 2024 18:40:14 +0200
Subject: [PATCH] QSaveFile[win]: Use SetFileInformationByHandle for atomic
 rename

With our previous setup we would CloseHandle the file handle and then
MoveFileEx the file to the final destination. This opens up the
opportunity for other processes to open the file in the meantime and
cause the MoveFileEx to fail.

With SetFileInformationByHandle we can, without closing the handle,
rename the file to the final destination.

Fixes: QTBUG-122208
Change-Id: Id3c8e0b5703da280c84e466ed88287e99788d077
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 9d8e233284aa9cd0757e1181451f4220473c71fe)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/io/qfsfileengine_p.h     |  3 +++
 src/corelib/io/qfsfileengine_win.cpp | 32 ++++++++++++++++++++++++++++
 src/corelib/io/qtemporaryfile.cpp    |  9 +++++++-
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/corelib/io/qfsfileengine_p.h b/src/corelib/io/qfsfileengine_p.h
index 7b43ff0bce8..732d3112462 100644
--- a/src/corelib/io/qfsfileengine_p.h
+++ b/src/corelib/io/qfsfileengine_p.h
@@ -151,6 +151,9 @@ public:
 #ifndef Q_OS_WIN
     bool isSequentialFdFh() const;
 #endif
+#ifdef Q_OS_WIN
+    bool nativeRenameOverwrite(const QString &newName) const;
+#endif
 
     uchar *map(qint64 offset, qint64 size, QFile::MemoryMapFlags flags);
     bool unmap(uchar *ptr);
diff --git a/src/corelib/io/qfsfileengine_win.cpp b/src/corelib/io/qfsfileengine_win.cpp
index 7a4f99cc7bb..3685a3cde59 100644
--- a/src/corelib/io/qfsfileengine_win.cpp
+++ b/src/corelib/io/qfsfileengine_win.cpp
@@ -27,6 +27,8 @@
 #define SECURITY_WIN32
 #include <security.h>
 
+#include <memory>
+
 #ifndef PATH_MAX
 #define PATH_MAX FILENAME_MAX
 #endif
@@ -394,6 +396,36 @@ bool QFSFileEnginePrivate::nativeIsSequential() const
             || (fileType == FILE_TYPE_PIPE);
 }
 
+bool QFSFileEnginePrivate::nativeRenameOverwrite(const QString &newName) const
+{
+    if (fileHandle == INVALID_HANDLE_VALUE)
+        return false;
+    QFileSystemEntry newEntry(newName, QFileSystemEntry::FromInternalPath());
+    const QString newFilePath = newEntry.nativeFilePath();
+    const size_t nameByteLength = newFilePath.length() * sizeof(wchar_t);
+    if (nameByteLength + sizeof(wchar_t) > std::numeric_limits<DWORD>::max())
+        return false;
+
+    constexpr size_t RenameInfoSize = sizeof(FILE_RENAME_INFO);
+    const size_t renameDataSize = RenameInfoSize + nameByteLength + sizeof(wchar_t);
+    QVarLengthArray<char> v(qsizetype(renameDataSize), 0);
+
+    auto *renameInfo = q20::construct_at(reinterpret_cast<FILE_RENAME_INFO *>(v.data()));
+    auto renameInfoRAII = qScopeGuard([&] { std::destroy_at(renameInfo); });
+    renameInfo->ReplaceIfExists = TRUE;
+    renameInfo->RootDirectory = nullptr;
+    renameInfo->FileNameLength = DWORD(nameByteLength);
+    memcpy(renameInfo->FileName, newFilePath.data(), nameByteLength);
+
+    bool res = SetFileInformationByHandle(fileHandle, FileRenameInfo, renameInfo,
+                                          DWORD(renameDataSize));
+#if 0
+    if (!res)
+        qErrnoWarning("QFSFileEnginePrivate::nativeRenameOverwrite failed");
+#endif
+    return res;
+}
+
 bool QFSFileEngine::caseSensitive() const
 {
     return false;
diff --git a/src/corelib/io/qtemporaryfile.cpp b/src/corelib/io/qtemporaryfile.cpp
index ff6a514fc9c..4bc21638f2d 100644
--- a/src/corelib/io/qtemporaryfile.cpp
+++ b/src/corelib/io/qtemporaryfile.cpp
@@ -184,8 +184,9 @@ static bool createFileFromTemplate(NativeFileHandle &file, QTemporaryFileName &t
         const DWORD shareMode = (flags & QTemporaryFileEngine::Win32NonShared)
                                 ? 0u : (FILE_SHARE_READ | FILE_SHARE_WRITE);
 
+        const DWORD extraAccessFlags = (flags & QTemporaryFileEngine::Win32NonShared) ? DELETE : 0;
         file = CreateFile((const wchar_t *)path.constData(),
-                GENERIC_READ | GENERIC_WRITE,
+                GENERIC_READ | GENERIC_WRITE | extraAccessFlags,
                 shareMode, NULL, CREATE_NEW,
                 FILE_ATTRIBUTE_NORMAL, NULL);
 
@@ -390,6 +391,12 @@ bool QTemporaryFileEngine::renameOverwrite(const QString &newName)
         QFSFileEngine::close();
         return ok;
     }
+#ifdef Q_OS_WIN
+    if (d_func()->nativeRenameOverwrite(newName)) {
+        QFSFileEngine::close();
+        return true;
+    }
+#endif
     QFSFileEngine::close();
     return QFSFileEngine::renameOverwrite(newName);
 }