avoid infinite recursion in canonicalized() if cwd is a symlink

if current directory is a symlink to another directory
on the same drive (the simplest example; say, c:\current\dir
is a symlink to c:\target) then the first valid prefix for
"c:\target" in canonicalized() is "c:" (NOT "c:\") and would
be treated like "c:\current\dir" again...and again...
until stack overflow :)

Merge-Request: 494
Task-number: QTBUG-7610
Reviewed-by: Zeno Albisser

2 files changed, 29 insertions, 3 deletions

diff --git a/src/corelib/io/qfsfileengine.cpp b/src/corelib/io/qfsfileengine.cpp
index 8689c57..d15b4a7 100644
--- a/src/corelib/io/qfsfileengine.cpp
+++ b/src/corelib/io/qfsfileengine.cpp
@@ -189,9 +189,15 @@ QString QFSFileEnginePrivate::canonicalized(const QString &path)
     known.insert(path);
     do {
 #ifdef Q_OS_WIN
-        // UNC, skip past the first two elements
-        if (separatorPos == 0 && tmpPath.startsWith(QLatin1String("//")))
-            separatorPos = tmpPath.indexOf(slash, 2);
+        if (separatorPos == 0) {
+            if (tmpPath.size() >= 2 && tmpPath.at(0) == slash && tmpPath.at(1) == slash) {
+                // UNC, skip past the first two elements
+                separatorPos = tmpPath.indexOf(slash, 2);
+            } else if (tmpPath.size() >= 3 && tmpPath.at(1) == QLatin1Char(':') && tmpPath.at(2) == slash) {
+                // volume root, skip since it can not be a symlink
+                separatorPos = 2;
+            }
+        }
         if (separatorPos != -1)
 #endif
         separatorPos = tmpPath.indexOf(slash, separatorPos + 1);
diff --git a/tests/auto/qfileinfo/tst_qfileinfo.cpp b/tests/auto/qfileinfo/tst_qfileinfo.cpp
index 6291f1c..af28848 100644
--- a/tests/auto/qfileinfo/tst_qfileinfo.cpp
+++ b/tests/auto/qfileinfo/tst_qfileinfo.cpp
@@ -46,6 +46,7 @@
 #include <qfile.h>
 #include <qdir.h>
 #include <qcoreapplication.h>
+#include <qlibrary.h>
 #include <qtemporaryfile.h>
 #include <qdir.h>
 #include <qfileinfo.h>
@@ -584,6 +585,25 @@ void tst_QFileInfo::canonicalFilePath()
     }
 #  endif
 #endif
+
+#ifdef Q_OS_WIN
+    typedef BOOL (WINAPI *PtrCreateSymbolicLink)(LPTSTR, LPTSTR, DWORD);
+    PtrCreateSymbolicLink ptrCreateSymbolicLink =
+            (PtrCreateSymbolicLink)QLibrary::resolve(QLatin1String("kernel32"), "CreateSymbolicLink");
+
+    if (!ptrCreateSymbolicLink ||
+        ptrCreateSymbolicLink((wchar_t*)QString("res").utf16(), (wchar_t*)QString("resources").utf16(), 1) == 0) {
+        QSKIP("Symbolic links aren't supported by FS", SkipAll);
+    }
+
+    QString currentPath = QDir::currentPath();
+    QCOMPARE(QDir::setCurrent("res"), true);
+
+    QCOMPARE(QFileInfo("file1").canonicalFilePath(), currentPath + "/resources/file1");
+
+    QCOMPARE(QDir::setCurrent(currentPath), true);
+    QFile::remove("res");
+#endif
 }
 
 void tst_QFileInfo::fileName_data()