From b4c8548fcd43419f5eed4f4fcda8b23f0cea1d1b Mon Sep 17 00:00:00 2001
From: Anton Filimonov <anton.filimonov@gmail.com>
Date: Wed, 24 Feb 2021 23:25:59 +0300
Subject: [PATCH] Add safety check for qChecksum (#228)

---
 3rdparty/singleapp/src/singleapplication_p.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/3rdparty/singleapp/src/singleapplication_p.cpp b/3rdparty/singleapp/src/singleapplication_p.cpp
index f4a1ca406..587120fb6 100644
--- a/3rdparty/singleapp/src/singleapplication_p.cpp
+++ b/3rdparty/singleapp/src/singleapplication_p.cpp
@@ -413,8 +413,11 @@ void SingleApplicationPrivate::readInitMessageBody( QLocalSocket *sock )
     quint16 msgChecksum = 0;
     readStream >> msgChecksum;
 
-    const quint16 actualChecksum = qChecksum( msgBytes.constData(), static_cast<quint32>( msgBytes.length() - sizeof( quint16 ) ) );
-
+    const quint16 actualChecksum = 
+        msgBytes.length() > sizeof( quint16 ) 
+            ? qChecksum( msgBytes.constData(), static_cast<quint32>( msgBytes.length() - sizeof( quint16 ) ) )
+            : 0;
+            
     bool isValid = readStream.status() == QDataStream::Ok &&
                    QLatin1String(latin1Name) == blockServerName &&
                    msgChecksum == actualChecksum;