Re: [PATCH] Make LIST_POISON less deadly

[Avi Kivity <avi@qumranet.com>]

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