Fixed a buffer overrun when pasting large data from non-Qt apps

When we receive a COMPOUND_TEXT data and convert it to multi-byte, if
the new length is less than the original buffer, we resize the buffer,
but then we need to make sure we reset the buffer_offset variable,
which is returned as a "size" of the buffer to a caller.

The conversion to COMPOUND_TEXT format was totally wrong, we were using
the wrong length of the input text, so the converted string was
truncated.

Task-number: QTBUG-8644
Reviewed-by: Bradley T. Hughes
(cherry picked from commit 4b81cb847647450f4bad8a0d9a278d43ebdfecc6)

4 files changed, 12 insertions, 16 deletions

diff --git a/src/gui/kernel/qclipboard_x11.cpp b/src/gui/kernel/qclipboard_x11.cpp
index 682b249f00..e3753175f8 100644
--- a/src/gui/kernel/qclipboard_x11.cpp
+++ b/src/gui/kernel/qclipboard_x11.cpp
@@ -597,7 +597,7 @@ static inline int maxSelectionIncr(Display *dpy)
 { return XMaxRequestSize(dpy) > 65536 ? 65536*4 : XMaxRequestSize(dpy)*4 - 100; }
 
 bool QX11Data::clipboardReadProperty(Window win, Atom property, bool deleteProperty,
-                                     QByteArray *buffer, int *size, Atom *type, int *format, bool nullterm)
+                                     QByteArray *buffer, int *size, Atom *type, int *format)
 {
     int           maxsize = maxSelectionIncr(display);
     ulong  bytes_left; // bytes_after
@@ -643,13 +643,13 @@ bool QX11Data::clipboardReadProperty(Window win, Atom property, bool deletePrope
         break;
     }
 
-    int newSize = proplen + (nullterm ? 1 : 0);
+    int newSize = proplen;
     buffer->resize(newSize);
 
     bool ok = (buffer->size() == newSize);
     VDEBUG("QClipboard: read_property(): buffer resized to %d", buffer->size());
 
-    if (ok) {
+    if (ok && newSize) {
         // could allocate buffer
 
         while (bytes_left) {
@@ -685,23 +685,19 @@ bool QX11Data::clipboardReadProperty(Window win, Atom property, bool deletePrope
             XTextProperty textprop;
             textprop.encoding = *type;
             textprop.format = *format;
-            textprop.nitems = length;
+            textprop.nitems = buffer_offset;
             textprop.value = (unsigned char *) buffer->data();
 
             char **list_ret = 0;
             int count;
             if (XmbTextPropertyToTextList(display, &textprop, &list_ret,
                          &count) == Success && count && list_ret) {
-                offset = strlen(list_ret[0]);
-                buffer->resize(offset + (nullterm ? 1 : 0));
+                offset = buffer_offset = strlen(list_ret[0]);
+                buffer->resize(offset);
                 memcpy(buffer->data(), list_ret[0], offset);
             }
             if (list_ret) XFreeStringList(list_ret);
         }
-
-        // zero-terminate (for text)
-        if (nullterm)
-            buffer->data()[buffer_offset] = '\0';
     }
 
     // correct size, not 0-term.
@@ -744,7 +740,7 @@ QByteArray QX11Data::clipboardReadIncrementalProperty(Window win, Atom property,
         if (event.xproperty.atom != property ||
              event.xproperty.state != PropertyNewValue)
             continue;
-        if (X11->clipboardReadProperty(win, property, true, &tmp_buf, &length, 0, 0, false)) {
+        if (X11->clipboardReadProperty(win, property, true, &tmp_buf, &length, 0, 0)) {
             if (length == 0) {                // no more data, we're done
                 if (nullterm) {
                     buf.resize(offset+1);
@@ -1072,7 +1068,7 @@ bool QClipboard::event(QEvent *e)
                 QByteArray multi_data;
                 if (req->property == XNone
                     || !X11->clipboardReadProperty(req->requestor, req->property, false, &multi_data,
-                                                   0, &multi_type, &multi_format, 0)
+                                                   0, &multi_type, &multi_format)
                     || multi_format != 32) {
                     // MULTIPLE property not formatted correctly
                     XSendEvent(dpy, req->requestor, False, NoEventMask, &event);
@@ -1294,7 +1290,7 @@ QByteArray QClipboardWatcher::getDataInFormat(Atom fmtatom) const
     Atom   type;
     XSelectInput(dpy, win, PropertyChangeMask);
 
-    if (X11->clipboardReadProperty(win, ATOM(_QT_SELECTION), true, &buf, 0, &type, 0, false)) {
+    if (X11->clipboardReadProperty(win, ATOM(_QT_SELECTION), true, &buf, 0, &type, 0)) {
         if (type == ATOM(INCR)) {
             int nbytes = buf.size() >= 4 ? *((int*)buf.data()) : 0;
             buf = X11->clipboardReadIncrementalProperty(win, ATOM(_QT_SELECTION), nbytes, false);
diff --git a/src/gui/kernel/qdnd_x11.cpp b/src/gui/kernel/qdnd_x11.cpp
index e6818180f4..330fb3e93e 100644
--- a/src/gui/kernel/qdnd_x11.cpp
+++ b/src/gui/kernel/qdnd_x11.cpp
@@ -1862,7 +1862,7 @@ static QVariant xdndObtainData(const char *format, QVariant::Type requestedType)
     if (got) {
         Atom type;
 
-        if (X11->clipboardReadProperty(tw->effectiveWinId(), ATOM(XdndSelection), true, &result, 0, &type, 0, false)) {
+        if (X11->clipboardReadProperty(tw->effectiveWinId(), ATOM(XdndSelection), true, &result, 0, &type, 0)) {
             if (type == ATOM(INCR)) {
                 int nbytes = result.size() >= 4 ? *((int*)result.data()) : 0;
                 result = X11->clipboardReadIncrementalProperty(tw->effectiveWinId(), ATOM(XdndSelection), nbytes, false);
diff --git a/src/gui/kernel/qmotifdnd_x11.cpp b/src/gui/kernel/qmotifdnd_x11.cpp
index ea8a8bc49a..b995f3bc60 100644
--- a/src/gui/kernel/qmotifdnd_x11.cpp
+++ b/src/gui/kernel/qmotifdnd_x11.cpp
@@ -766,7 +766,7 @@ QVariant QX11Data::motifdndObtainData(const char *mimeType)
     if (got) {
         Atom type;
 
-        if (X11->clipboardReadProperty(tw->internalWinId(), Dnd_selection, true, &result, 0, &type, 0, false)) {
+        if (X11->clipboardReadProperty(tw->internalWinId(), Dnd_selection, true, &result, 0, &type, 0)) {
         }
     }
 
diff --git a/src/gui/kernel/qt_x11_p.h b/src/gui/kernel/qt_x11_p.h
index e752e3c4cf..8e484d6fd0 100644
--- a/src/gui/kernel/qt_x11_p.h
+++ b/src/gui/kernel/qt_x11_p.h
@@ -350,7 +350,7 @@ struct QX11Data
     // from qclipboard_x11.cpp
     bool clipboardWaitForEvent(Window win, int type, XEvent *event, int timeout);
     bool clipboardReadProperty(Window win, Atom property, bool deleteProperty,
-                            QByteArray *buffer, int *size, Atom *type, int *format, bool nullterm);
+                            QByteArray *buffer, int *size, Atom *type, int *format);
     QByteArray clipboardReadIncrementalProperty(Window win, Atom property, int nbytes, bool nullterm);
 
     // from qdnd_x11.cpp