Bug 135040 – inserting an SVGLength that is already in an SVGAnimatedLengthList::animVal into another list causes a crash

• Component: SVG
• Status: RESOLVED DUPLICATE

[Cameron McCormack (:heycam)]

STR:

1. Load the URL.
2. Crash.

Attempting to insert an SVGLength that came from an SVGAnimatedLengthList's animVal into another SVGLengthList will cause a crash.  I haven't looked to see if the crash is serious.  Tested with Safari 7.0.5 (9537.77.4).

[Darin Adler]

This crash is a null dereference; I doubt there is any security implication, and I suspect this is mis-categorized as a security bug.

The bug seems to be in code in SVGListPropertyTearOff::processIncomingListItemWrapper, which calls SVGAnimatedListPropertyTearOff::findItem, which can’t handle an m_baseVal of nullptr. If I knew this code better, I might suggest fixing this by calling baseVal() inside findItem and in removeItemFromList rather than accessing m_baseVal directly.

[Dirk Schulze]

(In reply to comment #1)
> This crash is a null dereference; I doubt there is any security implication, and I suspect this is mis-categorized as a security bug.
> 
> The bug seems to be in code in SVGListPropertyTearOff::processIncomingListItemWrapper, which calls SVGAnimatedListPropertyTearOff::findItem, which can’t handle an m_baseVal of nullptr. If I knew this code better, I might suggest fixing this by calling baseVal() inside findItem and in removeItemFromList rather than accessing m_baseVal directly.

I asked Cameron to open it as security bug since I couldn't test it myself yet. If you have evidence that it is a normal crash, please re-categorize it.

[Darin Adler]

OK, done.

[Darin Adler]

Created attachment 235179 [details]
local copy of test case

[Darin Adler]

Crashes after trying to access a data member of m_baseVal, which is nullptr.

[Zoltan Horvath]

Blink doesn't have the issue, probably because of some refactoring on this code. Merge candidate tracked in: https://bugs.webkit.org/show_bug.cgi?id=125888

[Said Abou-Hallawa]

After https://bugs.webkit.org/show_bug.cgi?id=191237 is fixed and when opening the attached test case in WebKit, I get the following output:

appending an SVG item that is in an animVal list of another element:
  - animVal list item remained the same object
  - an item was appended
  - the appended item was a copy of the animVal list item

This is complies with SVG 2 specs: https://www.w3.org/TR/SVG2/types.html#__svg__SVGNameList__appendItem. Also this is the behavior of FireFox.

*** This bug has been marked as a duplicate of bug 191237 ***