[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

Darin Adler <darin at apple.com> changed:

           What    |Removed                     |Added
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--- Comment #2 from Darin Adler <darin at apple.com> ---
Comment on attachment 439616
  --> https://bugs.webkit.org/attachment.cgi?id=439616
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=439616&action=review

> Source/WebCore/ChangeLog:4
> +        Nullptr deref when accessing m_value.calc in CSSPrimitiveValue::primitiveType()
> +        https://bugs.webkit.org/show_bug.cgi?id=230929

Overall this doesn’t look right. Type set to CSS_CALC, but calc pointer set to nullptr is an invalid state, and changing all the functions to support that isn’t the correct solution.

Instead I suggest we focus on how we end up in this state and preventing us from doing so.

> Source/WebCore/css/CSSPrimitiveValue.cpp:436
> -    m_value.calc = c.leakRef();
> +    if (c)
> +        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.

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