qputenv: defend against non-NUL-terminated QByteArray values

The old code assumed that a QByteArray's data() is always
NUL-terminated. Due to the conflation of owners and non-owners in
QByteArray (but also in case we ever get efficient substringing), this
is not always the case, e.g. QByteArray::fromRawData() does not ensure
NUL-termination.

From QString::utf16(), we learn that the condition to check for is
QArrayData::isMutable(). After working around the fact that
QByteArray::data_ptr() doesn't exist for const QBAs and that empty
QBAs always refer to QByteArray::empty_, which is !isMutable(), we can
detect this situation and re-allocate without introducing new API.

This is the fix for Qt ≤ 6.4. For Qt 6.5, we'll port the function to
QByteArrayView.

Manual conflict resolutions:
  - tracked changes into qglobal.cpp (was: qenvionmentvariables.cpp)

Fixes: QTBUG-105302
Change-Id: I3416535ab09d601e0e87b2767f2c024ba1217e64
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit 15422d191fb03eb9cafe68b24484d59c1270244c)

1 files changed, 8 insertions, 0 deletions

diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index d2805f52e1..3d880fdb46 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -3619,6 +3619,14 @@ bool qEnvironmentVariableIsSet(const char *varName) noexcept
 */
 bool qputenv(const char *varName, const QByteArray &value)
 {
+    // protect against non-NUL-terminated QByteArrays:
+    if (!const_cast<QByteArray&>(value).data_ptr()->isMutable()) {
+        QByteArray copy(value);
+        copy.reserve(copy.size() + 1); // ensures NUL termination (and isMutable() even for size==0
+                                       // (unlike detach()) to avoid infinite recursion)
+        return qputenv(varName, copy);
+    }
+
 #if defined(Q_CC_MSVC)
     const auto locker = qt_scoped_lock(environmentMutex);
     return _putenv_s(varName, value.constData()) == 0;