[Webkit-unassigned] [Bug 89502] New: Overflow RenderLayers are not allocated in SVG leading to multiple crashers

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=89502

           Summary: Overflow RenderLayers are not allocated in SVG leading
                    to multiple crashers
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jchaffraix at webkit.org
                CC: eric at webkit.org, zimmermann at kde.org, krit at webkit.org,
                    simon.fraser at apple.com, jamesr at chromium.org,
                    enne at google.com


Created an attachment (id=148399)
 --> (https://bugs.webkit.org/attachment.cgi?id=148399&action=review)
Example test case - beware that it will crash

Following bug 75568, we added a lot of NULL-check for overflow clip layers. Incidentally this solved a lot of NULL crashers due to us NULL-checking the layer() instead of calling it directly. Bug 75568 was rolled out in bug 83954 so we are back to crashing, except that people started depending on this to work and consider this to be a regression.

The core issue is that even if requiresLayer() returns true, we are not guaranteed to have a RenderLayer as it's also determined by RenderObject::layerCreationAllowedForSubtree() (which can return false in SVG documents). One way would be to make RenderLayer work in SVG but it's likely not a good idea as RenderLayer is very CSS specific.

My view on the issue is to re-add the NULL-checks while we determine a better solution.

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