Fix out of buffer access in qt_qimageScaleRgba64_up_xy

Avoid reading a pixel outside the image even if we multiply the result
by 0. This mirrors a similar old fix in the the 32bit scaling path.

Change-Id: I7860bc808dc46dbc94918672e99c81b56d4a1d27
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/gui/painting/qimagescale.cpp b/src/gui/painting/qimagescale.cpp
index ca7930500e..96da5e029c 100644
--- a/src/gui/painting/qimagescale.cpp
+++ b/src/gui/painting/qimagescale.cpp
@@ -564,7 +564,10 @@ static void qt_qimageScaleRgba64_up_xy(QImageScaleInfo *isi, QRgba64 *dest,
             for (int x = 0; x < dw; x++) {
                 const QRgba64 *pix = sptr + xpoints[x];
                 const int xap = xapoints[x];
-                *dptr = interpolate256(pix[0], 256 - xap, pix[1], xap);
+                if (xap > 0)
+                    *dptr = interpolate256(pix[0], 256 - xap, pix[1], xap);
+                else
+                    *dptr = pix[0];
                 dptr++;
             }
         }