linux-kernel - Re: [PATCH] Make LIST

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Message-ID: <20080520164758.GA8531@elf.ucw.cz>
Date:	Tue, 20 May 2008 18:47:58 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	Avi Kivity <avi@...ranet.com>
Cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make LIST_POISON less deadly

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).
								Pavel

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