[Webkit-unassigned] [Bug 230929] Nullptr deref when accessing m_value.calc in CSSPrimitiveValue::primitiveType()

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=230929

--- Comment #6 from Gabriel Nava Marino <gnavamarino at apple.com> ---
(In reply to Darin Adler from comment #4)
> Comment on attachment 439616 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=439616&action=review
> 
> >>> Source/WebCore/css/CSSPrimitiveValue.cpp:436
> >>> +        m_value.calc = c.leakRef();
> >> 
> >> This specific change is either is a no-op or seems pretty dangerous. It will leave m_value.calc uninitialized if this is called with nullptr. That’s not *better* than setting it to nullptr.
> > 
> > 
> 
> Thinking further about this, even if we fix the true cause of the null
> CSSCalcValue, I suggest we also change this init function to either take
> Ref<CSSCalcValue> instead of RefPtr<CSSCalcValue>, like all the other init
> functions, or change it so that if it’s passed nullptr it returns early and
> does nothing, leaving the primitive unit type set to the default CSS_UNKNOWN.


Thank you for the suggestions! I will proceed with the second recommended approach to fix this particular bug, by returning early if we have a nullptr. However, I have filed https://bugs.webkit.org/show_bug.cgi?id=231111 to track the first approach.

I have also verified the updated patch resolves the crash referenced in this bug.

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