Avoid out of bounds memory reads when scaling imagesv4.8.6

The calculation of the width/height required for the
scaling algorithm was prone to floating point rounding
issues, where the lower value got rounded down, the higher
one rounded up. This could lead to a situation where we
iterated over one more line/pixel in the line than we have
in the source image.

Correct this by passing the dimension of the source image into
the function and bounds checking the values before iterating.

Backport of If44b2235a479224660d508a0504fec40d724763a from Qt 5

Task-number: QTBUG-35927
Change-Id: If145ee715a143b889538243f45227d8d78a0050f
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

6 files changed, 45 insertions, 27 deletions

diff --git a/src/gui/painting/qblendfunctions.cpp b/src/gui/painting/qblendfunctions.cpp
index 6f0fe1e..e11990f 100644
--- a/src/gui/painting/qblendfunctions.cpp
+++ b/src/gui/painting/qblendfunctions.cpp
@@ -179,7 +179,7 @@ struct Blend_ARGB32_on_RGB16_SourceAndConstAlpha {
 };
 
 void qt_scale_image_rgb16_on_rgb16(uchar *destPixels, int dbpl,
-                                   const uchar *srcPixels, int sbpl,
+                                   const uchar *srcPixels, int sbpl, int sh,
                                    const QRectF &targetRect,
                                    const QRectF &sourceRect,
                                    const QRect &clip,
@@ -194,17 +194,17 @@ void qt_scale_image_rgb16_on_rgb16(uchar *destPixels, int dbpl,
 #endif
     if (const_alpha == 256) {
         Blend_RGB16_on_RGB16_NoAlpha noAlpha;
-        qt_scale_image_16bit<quint16>(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_16bit<quint16>(destPixels, dbpl, srcPixels, sbpl, sh,
                                       targetRect, sourceRect, clip, noAlpha);
     } else {
         Blend_RGB16_on_RGB16_ConstAlpha constAlpha(const_alpha);
-        qt_scale_image_16bit<quint16>(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_16bit<quint16>(destPixels, dbpl, srcPixels, sbpl, sh,
                                      targetRect, sourceRect, clip, constAlpha);
     }
 }
 
 void qt_scale_image_argb24_on_rgb16(uchar *destPixels, int dbpl,
-                                   const uchar *srcPixels, int sbpl,
+                                   const uchar *srcPixels, int sbpl, int sh,
                                    const QRectF &targetRect,
                                    const QRectF &sourceRect,
                                    const QRect &clip,
@@ -219,18 +219,18 @@ void qt_scale_image_argb24_on_rgb16(uchar *destPixels, int dbpl,
 #endif
     if (const_alpha == 256) {
         Blend_ARGB24_on_RGB16_SourceAlpha noAlpha;
-        qt_scale_image_16bit<qargb8565>(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_16bit<qargb8565>(destPixels, dbpl, srcPixels, sbpl, sh,
                                         targetRect, sourceRect, clip, noAlpha);
     } else {
         Blend_ARGB24_on_RGB16_SourceAndConstAlpha constAlpha(const_alpha);
-        qt_scale_image_16bit<qargb8565>(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_16bit<qargb8565>(destPixels, dbpl, srcPixels, sbpl, sh,
                                         targetRect, sourceRect, clip, constAlpha);
     }
 }
 
 
 void qt_scale_image_argb32_on_rgb16(uchar *destPixels, int dbpl,
-                                    const uchar *srcPixels, int sbpl,
+                                    const uchar *srcPixels, int sbpl, int sh,
                                     const QRectF &targetRect,
                                     const QRectF &sourceRect,
                                     const QRect &clip,
@@ -245,11 +245,11 @@ void qt_scale_image_argb32_on_rgb16(uchar *destPixels, int dbpl,
 #endif
     if (const_alpha == 256) {
         Blend_ARGB32_on_RGB16_SourceAlpha noAlpha;
-        qt_scale_image_16bit<quint32>(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_16bit<quint32>(destPixels, dbpl, srcPixels, sbpl, sh,
                                       targetRect, sourceRect, clip, noAlpha);
     } else {
         Blend_ARGB32_on_RGB16_SourceAndConstAlpha constAlpha(const_alpha);
-        qt_scale_image_16bit<quint32>(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_16bit<quint32>(destPixels, dbpl, srcPixels, sbpl, sh,
                                      targetRect, sourceRect, clip, constAlpha);
     }
 }
@@ -611,7 +611,7 @@ struct Blend_ARGB32_on_ARGB32_SourceAndConstAlpha {
 };
 
 void qt_scale_image_rgb32_on_rgb32(uchar *destPixels, int dbpl,
-                                   const uchar *srcPixels, int sbpl,
+                                   const uchar *srcPixels, int sbpl, int sh,
                                    const QRectF &targetRect,
                                    const QRectF &sourceRect,
                                    const QRect &clip,
@@ -626,17 +626,17 @@ void qt_scale_image_rgb32_on_rgb32(uchar *destPixels, int dbpl,
 #endif
     if (const_alpha == 256) {
         Blend_RGB32_on_RGB32_NoAlpha noAlpha;
-        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl, sh,
                              targetRect, sourceRect, clip, noAlpha);
     } else {
         Blend_RGB32_on_RGB32_ConstAlpha constAlpha(const_alpha);
-        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl, sh,
                              targetRect, sourceRect, clip, constAlpha);
     }
 }
 
 void qt_scale_image_argb32_on_argb32(uchar *destPixels, int dbpl,
-                                     const uchar *srcPixels, int sbpl,
+                                     const uchar *srcPixels, int sbpl, int sh,
                                      const QRectF &targetRect,
                                      const QRectF &sourceRect,
                                      const QRect &clip,
@@ -651,11 +651,11 @@ void qt_scale_image_argb32_on_argb32(uchar *destPixels, int dbpl,
 #endif
     if (const_alpha == 256) {
         Blend_ARGB32_on_ARGB32_SourceAlpha sourceAlpha;
-        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl, sh,
                              targetRect, sourceRect, clip, sourceAlpha);
     } else {
         Blend_ARGB32_on_ARGB32_SourceAndConstAlpha constAlpha(const_alpha);
-        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl,
+        qt_scale_image_32bit(destPixels, dbpl, srcPixels, sbpl, sh,
                              targetRect, sourceRect, clip, constAlpha);
     }
 }
diff --git a/src/gui/painting/qblendfunctions_p.h b/src/gui/painting/qblendfunctions_p.h
index ef5aca0..5d20cea 100644
--- a/src/gui/painting/qblendfunctions_p.h
+++ b/src/gui/painting/qblendfunctions_p.h
@@ -60,7 +60,7 @@ QT_BEGIN_NAMESPACE
 
 template <typename SRC, typename T>
 void qt_scale_image_16bit(uchar *destPixels, int dbpl,
-                          const uchar *srcPixels, int sbpl,
+                          const uchar *srcPixels, int sbpl, int sh,
                           const QRectF &targetRect,
                           const QRectF &srcRect,
                           const QRect &clip,
@@ -136,6 +136,15 @@ void qt_scale_image_16bit(uchar *destPixels, int dbpl,
 
     quint16 *dst = ((quint16 *) (destPixels + ty1 * dbpl)) + tx1;
 
+    // this bounds check here is required as floating point rounding above might in some cases lead to
+    // w/h values that are one pixel too large, falling outside of the valid image area.
+    int yend = (srcy + iy * (h - 1)) >> 16;
+    if (yend < 0 || yend >= sh)
+        --h;
+    int xend = (basex + ix * (w - 1)) >> 16;
+    if (xend < 0 || xend >= (int)(sbpl/sizeof(quint32)))
+        --w;
+
     while (h--) {
         const SRC *src = (const SRC *) (srcPixels + (srcy >> 16) * sbpl);
         int srcx = basex;
@@ -161,7 +170,7 @@ void qt_scale_image_16bit(uchar *destPixels, int dbpl,
 }
 
 template <typename T> void qt_scale_image_32bit(uchar *destPixels, int dbpl,
-                                                const uchar *srcPixels, int sbpl,
+                                                const uchar *srcPixels, int sbpl, int sh,
                                                 const QRectF &targetRect,
                                                 const QRectF &srcRect,
                                                 const QRect &clip,
@@ -236,6 +245,15 @@ template <typename T> void qt_scale_image_32bit(uchar *destPixels, int dbpl,
 
     quint32 *dst = ((quint32 *) (destPixels + ty1 * dbpl)) + tx1;
 
+    // this bounds check here is required as floating point rounding above might in some cases lead to
+    // w/h values that are one pixel too large, falling outside of the valid image area.
+    int yend = (srcy + iy * (h - 1)) >> 16;
+    if (yend < 0 || yend >= sh)
+        --h;
+    int xend = (basex + ix * (w - 1)) >> 16;
+    if (xend < 0 || xend >= (int)(sbpl/sizeof(quint32)))
+        --w;
+
     while (h--) {
         const uint *src = (const quint32 *) (srcPixels + (srcy >> 16) * sbpl);
         int srcx = basex;
diff --git a/src/gui/painting/qdrawhelper_neon.cpp b/src/gui/painting/qdrawhelper_neon.cpp
index 48853f1..e3e74d0 100644
--- a/src/gui/painting/qdrawhelper_neon.cpp
+++ b/src/gui/painting/qdrawhelper_neon.cpp
@@ -539,7 +539,7 @@ Blend_on_RGB16_SourceAndConstAlpha_Neon_create(BlendFunc blender, int const_alph
 }
 
 void qt_scale_image_argb32_on_rgb16_neon(uchar *destPixels, int dbpl,
-                                         const uchar *srcPixels, int sbpl,
+                                         const uchar *srcPixels, int sbpl, int sh,
                                          const QRectF &targetRect,
                                          const QRectF &sourceRect,
                                          const QRect &clip,
@@ -548,19 +548,19 @@ void qt_scale_image_argb32_on_rgb16_neon(uchar *destPixels, int dbpl,
     if (const_alpha == 0)
         return;
 
-    qt_scale_image_16bit<quint32>(destPixels, dbpl, srcPixels, sbpl, targetRect, sourceRect, clip,
+    qt_scale_image_16bit<quint32>(destPixels, dbpl, srcPixels, sbpl, sh, targetRect, sourceRect, clip,
         Blend_on_RGB16_SourceAndConstAlpha_Neon_create<quint32>(blend_8_pixels_argb32_on_rgb16_neon, const_alpha));
 }
 
 void qt_scale_image_rgb16_on_rgb16(uchar *destPixels, int dbpl,
-                                   const uchar *srcPixels, int sbpl,
+                                   const uchar *srcPixels, int sbpl, int sh,
                                    const QRectF &targetRect,
                                    const QRectF &sourceRect,
                                    const QRect &clip,
                                    int const_alpha);
 
 void qt_scale_image_rgb16_on_rgb16_neon(uchar *destPixels, int dbpl,
-                                        const uchar *srcPixels, int sbpl,
+                                        const uchar *srcPixels, int sbpl, int sh,
                                         const QRectF &targetRect,
                                         const QRectF &sourceRect,
                                         const QRect &clip,
@@ -570,11 +570,11 @@ void qt_scale_image_rgb16_on_rgb16_neon(uchar *destPixels, int dbpl,
         return;
 
     if (const_alpha == 256) {
-        qt_scale_image_rgb16_on_rgb16(destPixels, dbpl, srcPixels, sbpl, targetRect, sourceRect, clip, const_alpha);
+        qt_scale_image_rgb16_on_rgb16(destPixels, dbpl, srcPixels, sbpl, sh, targetRect, sourceRect, clip, const_alpha);
         return;
     }
 
-    qt_scale_image_16bit<quint16>(destPixels, dbpl, srcPixels, sbpl, targetRect, sourceRect, clip,
+    qt_scale_image_16bit<quint16>(destPixels, dbpl, srcPixels, sbpl, sh, targetRect, sourceRect, clip,
         Blend_on_RGB16_SourceAndConstAlpha_Neon_create<quint16>(blend_8_pixels_rgb16_on_rgb16_neon, const_alpha));
 }
 
diff --git a/src/gui/painting/qdrawhelper_neon_p.h b/src/gui/painting/qdrawhelper_neon_p.h
index 83be25e..360b5ce 100644
--- a/src/gui/painting/qdrawhelper_neon_p.h
+++ b/src/gui/painting/qdrawhelper_neon_p.h
@@ -96,14 +96,14 @@ void qt_alphamapblit_quint16_neon(QRasterBuffer *rasterBuffer,
                                   const QClipData *clip);
 
 void qt_scale_image_argb32_on_rgb16_neon(uchar *destPixels, int dbpl,
-                                         const uchar *srcPixels, int sbpl,
+                                         const uchar *srcPixels, int sbpl, int sh,
                                          const QRectF &targetRect,
                                          const QRectF &sourceRect,
                                          const QRect &clip,
                                          int const_alpha);
 
 void qt_scale_image_rgb16_on_rgb16_neon(uchar *destPixels, int dbpl,
-                                        const uchar *srcPixels, int sbpl,
+                                        const uchar *srcPixels, int sbpl, int sh,
                                         const QRectF &targetRect,
                                         const QRectF &sourceRect,
                                         const QRect &clip,
diff --git a/src/gui/painting/qdrawhelper_p.h b/src/gui/painting/qdrawhelper_p.h
index 2e346d1..f80bfcb 100644
--- a/src/gui/painting/qdrawhelper_p.h
+++ b/src/gui/painting/qdrawhelper_p.h
@@ -138,7 +138,7 @@ typedef void (*SrcOverBlendFunc)(uchar *destPixels, int dbpl,
                                  int const_alpha);
 
 typedef void (*SrcOverScaleFunc)(uchar *destPixels, int dbpl,
-                                 const uchar *src, int spbl,
+                                 const uchar *src, int spbl, int srch,
                                  const QRectF &targetRect,
                                  const QRectF &sourceRect,
                                  const QRect &clipRect,
diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 6cbf995..f715c14 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -2369,7 +2369,7 @@ void QRasterPaintEngine::drawImage(const QRectF &r, const QImage &img, const QRe
                 SrcOverScaleFunc func = qScaleFunctions[d->rasterBuffer->format][img.format()];
                 if (func && (!clip || clip->hasRectClip)) {
                     func(d->rasterBuffer->buffer(), d->rasterBuffer->bytesPerLine(),
-                         img.bits(), img.bytesPerLine(),
+                         img.bits(), img.bytesPerLine(), img.height(),
                          qt_mapRect_non_normalizing(r, s->matrix), sr,
                          !clip ? d->deviceRect : clip->clipRect,
                          s->intOpacity);