Changeset 160335 in webkit

Timestamp:

Dec 9, 2013, 3:27:42 PM (12 years ago)

Author:

Simon Fraser

Message:

Avoid divide by zero in scrollbar code, and protect against Obj-C exceptions
​https://bugs.webkit.org/show_bug.cgi?id=125469
<rdar://problem/15535772>

Reviewed by Beth Dakin.

In ScrollbarThemeMac::setPaintCharacteristicsForScrollbar(), proportion could
end up as NaN if scrollbar->totalSize() were zero. Protect against that.

Also wrap functions that call into Objective-C with BEGIN_BLOCK_OBJC_EXCEPTIONS/
END_BLOCK_OBJC_EXCEPTIONS.

• platform/mac/ScrollbarThemeMac.mm:

(WebCore::ScrollbarThemeMac::scrollbarThickness):
(WebCore::ScrollbarThemeMac::updateScrollbarOverlayStyle):
(WebCore::ScrollbarThemeMac::minimumThumbLength):
(WebCore::ScrollbarThemeMac::updateEnabledState):
(WebCore::ScrollbarThemeMac::setPaintCharacteristicsForScrollbar):
(WebCore::scrollbarPainterPaint):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/mac/ScrollbarThemeMac.mm (modified) (9 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2013-12-09  Simon Fraser  <simon.fraser@apple.com>
+
+        Avoid divide by zero in scrollbar code, and protect against Obj-C exceptions
+        https://bugs.webkit.org/show_bug.cgi?id=125469
+        <rdar://problem/15535772>
+
+        Reviewed by Beth Dakin.
+        
+        In ScrollbarThemeMac::setPaintCharacteristicsForScrollbar(), proportion could
+        end up as NaN if scrollbar->totalSize() were zero. Protect against that.
+        
+        Also wrap functions that call into Objective-C with BEGIN_BLOCK_OBJC_EXCEPTIONS/
+        END_BLOCK_OBJC_EXCEPTIONS.
+
+        * platform/mac/ScrollbarThemeMac.mm:
+        (WebCore::ScrollbarThemeMac::scrollbarThickness):
+        (WebCore::ScrollbarThemeMac::updateScrollbarOverlayStyle):
+        (WebCore::ScrollbarThemeMac::minimumThumbLength):
+        (WebCore::ScrollbarThemeMac::updateEnabledState):
+        (WebCore::ScrollbarThemeMac::setPaintCharacteristicsForScrollbar):
+        (WebCore::scrollbarPainterPaint):
+
 2013-12-09  Ryosuke Niwa  <rniwa@webkit.org>
 

trunk/Source/WebCore/platform/mac/ScrollbarThemeMac.mm

@@ -27 +27 @@
 #include "ScrollbarThemeMac.h"
 
+#include "BlockExceptions.h"
 #include "ColorMac.h"
 #include "ImageBuffer.h"
@@ -222 +223 @@
 int ScrollbarThemeMac::scrollbarThickness(ScrollbarControlSize controlSize)
 {
+    BEGIN_BLOCK_OBJC_EXCEPTIONS;
     ScrollbarPainter scrollbarPainter = [NSClassFromString(@"NSScrollerImp") scrollerImpWithStyle:recommendedScrollerStyle() controlSize:controlSize horizontal:NO replacingScrollerImp:nil];
     if (supportsExpandedScrollbars())
         [scrollbarPainter setExpanded:YES];
     return [scrollbarPainter trackBoxWidth];
+    END_BLOCK_OBJC_EXCEPTIONS;
 }
 
@@ -240 +243 @@
 void ScrollbarThemeMac::updateScrollbarOverlayStyle(ScrollbarThemeClient* scrollbar)
 {
+    BEGIN_BLOCK_OBJC_EXCEPTIONS;
     ScrollbarPainter painter = painterForScrollbar(scrollbar);
     switch (scrollbar->scrollbarOverlayStyle()) {
@@ -252 +256 @@
         break;
     }
+    END_BLOCK_OBJC_EXCEPTIONS;
 }
 
@@ -421 +426 @@
 int ScrollbarThemeMac::minimumThumbLength(ScrollbarThemeClient* scrollbar)
 {
+    BEGIN_BLOCK_OBJC_EXCEPTIONS;
     return [scrollbarMap()->get(scrollbar) knobMinLength];
+    END_BLOCK_OBJC_EXCEPTIONS;
 }
 
@@ -458 +465 @@
 void ScrollbarThemeMac::updateEnabledState(ScrollbarThemeClient* scrollbar)
 {
+    BEGIN_BLOCK_OBJC_EXCEPTIONS;
     [scrollbarMap()->get(scrollbar) setEnabled:scrollbar->enabled()];
+    END_BLOCK_OBJC_EXCEPTIONS;
 }
 
 void ScrollbarThemeMac::setPaintCharacteristicsForScrollbar(ScrollbarThemeClient* scrollbar)
 {
+    BEGIN_BLOCK_OBJC_EXCEPTIONS;
     ScrollbarPainter painter = painterForScrollbar(scrollbar);
 
@@ -468 +478 @@
     float overhang;
     ScrollableArea::computeScrollbarValueAndOverhang(scrollbar->currentPos(), scrollbar->totalSize(), scrollbar->visibleSize(), value, overhang);
-    float proportion = (static_cast<CGFloat>(scrollbar->visibleSize()) - overhang) / scrollbar->totalSize();
+    float proportion = scrollbar->totalSize() > 0 ? (static_cast<CGFloat>(scrollbar->visibleSize()) - overhang) / scrollbar->totalSize() : 1;
 
     [painter setEnabled:scrollbar->enabled()];
@@ -474 +484 @@
     [painter setDoubleValue:value];
     [painter setKnobProportion:proportion];
+    END_BLOCK_OBJC_EXCEPTIONS;
 }
 
 static void scrollbarPainterPaint(ScrollbarPainter scrollbarPainter, bool enabled)
 {
+    BEGIN_BLOCK_OBJC_EXCEPTIONS;
     // Use rectForPart: here; it will take the expansion transition progress into account.
     NSRect trackRect = [scrollbarPainter rectForPart:NSScrollerKnobSlot];
@@ -486 +498 @@
     if (enabled)
         [scrollbarPainter drawKnob];
+    END_BLOCK_OBJC_EXCEPTIONS;
 }