From c62c335be44a8b71f590f1ee1c13a8d5c771e3c6 Mon Sep 17 00:00:00 2001
From: Ivan Solovev <ivan.solovev@qt.io>
Date: Thu, 2 Nov 2023 14:36:02 +0100
Subject: [PATCH] QSharedMemory: fix semaphore creation in legacy mode
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The legacy mode was using the new nativeKey to create a semaphore.
As a result, on macOS the name of the semaphore key file was the same
as the name of the shared memory key file.
This lead to a situation when the file was mistakenly deleted when
destroying any instance of the shared memory, not only the one that
created it.
Fix it by using QSystemSemaphore::legacyNativeKey() in legacy mode.

Add a test to verify that we cannot re-create a shared memory with the
same key. The test was failing on macOS without the fix.

Fixes: QTBUG-111855
Change-Id: Ib0bc41791e889b1888bbb8aa9044c6b053b63a5a
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 02c42b26e1ff94047657c4838128cb5b22d24d2b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/ipc/qsharedmemory.cpp             |  6 ++++-
 .../ipc/qsharedmemory/tst_qsharedmemory.cpp   | 26 +++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/corelib/ipc/qsharedmemory.cpp b/src/corelib/ipc/qsharedmemory.cpp
index 8dcdc43e180..379379464e1 100644
--- a/src/corelib/ipc/qsharedmemory.cpp
+++ b/src/corelib/ipc/qsharedmemory.cpp
@@ -258,7 +258,11 @@ bool QSharedMemoryPrivate::initKey(SemaphoreAccessMode mode)
     if (!cleanHandle())
         return false;
 #if QT_CONFIG(systemsemaphore)
-    systemSemaphore.setNativeKey(semaphoreNativeKey(), 1, mode);
+    const QString legacyKey = QNativeIpcKeyPrivate::legacyKey(nativeKey);
+    const QNativeIpcKey semKey = legacyKey.isEmpty()
+            ? semaphoreNativeKey()
+            : QSystemSemaphore::legacyNativeKey(legacyKey, nativeKey.type());
+    systemSemaphore.setNativeKey(semKey, 1, mode);
     if (systemSemaphore.error() != QSystemSemaphore::NoError) {
         QString function = "QSharedMemoryPrivate::initKey"_L1;
         errorString = QSharedMemory::tr("%1: unable to set key on lock (%2)")
diff --git a/tests/auto/corelib/ipc/qsharedmemory/tst_qsharedmemory.cpp b/tests/auto/corelib/ipc/qsharedmemory/tst_qsharedmemory.cpp
index 4c871e02699..cdbc4e5d8b3 100644
--- a/tests/auto/corelib/ipc/qsharedmemory/tst_qsharedmemory.cpp
+++ b/tests/auto/corelib/ipc/qsharedmemory/tst_qsharedmemory.cpp
@@ -78,6 +78,9 @@ private slots:
     void uniqueKey_data();
     void uniqueKey();
 
+    // legacy
+    void createWithSameKey();
+
 protected:
     void remove(const QNativeIpcKey &key);
 
@@ -899,6 +902,29 @@ void tst_QSharedMemory::uniqueKey()
     QCOMPARE(nativeEqual, setEqual);
 }
 
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_DEPRECATED
+void tst_QSharedMemory::createWithSameKey()
+{
+    const QString key = u"legacy_key"_s;
+    const qsizetype sz = 100;
+    QSharedMemory mem1(key);
+    QVERIFY(mem1.create(sz));
+
+    {
+        QSharedMemory mem2(key);
+        QVERIFY(!mem2.create(sz));
+        QVERIFY(mem2.attach());
+    }
+    // and the second create() should fail as well, QTBUG-111855
+    {
+        QSharedMemory mem2(key);
+        QVERIFY(!mem2.create(sz));
+        QVERIFY(mem2.attach());
+    }
+}
+QT_WARNING_POP
+
 QTEST_MAIN(tst_QSharedMemory)
 #include "tst_qsharedmemory.moc"