linux-kernel - Re: [PATCH] Make LIST

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Date:	Tue, 20 May 2008 19:50:05 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Pavel Machek <pavel@...e.cz>
CC:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make LIST_POISON less deadly

Pavel Machek wrote:
> 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...
>   

It's a potential security hole.  You need to find a list corruption 
first.  The patch prevents escalation of the oops into a code injection.

i386 is fixable, though it will take more work than x86_64.

-- 
error compiling committee.c: too many arguments to function

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