Re: [PATCH] Make LIST_POISON less deadly

From: Pavel Machek
Date: Tue May 20 2008 - 12:47:20 EST

On Sun 2008-05-18 18:38:14, Avi Kivity wrote:
> The list macros use LIST_POISON1 and LIST_POISON2 as undereferencable
> pointers in order to trap erronous use of freed list_heads. Unfortunately
> userspace can arrange for those pointers to actually be dereferencable,
> potentially turning an oops to an expolit.
> To avoid this allow architectures (currently x86_64 only) to override
> the default values for these pointers with truly-undereferncable values.
> This is easy on x86_64 as the virtual address space is smaller than
> the range spanned by pointer values.

"Security hole unless arch maintainer does _foo_" sounds
scary. Especially when i386 is hard to fix...

(And very nice catch, btw).

(cesky, pictures)
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