linux-kernel - Re: [PATCH] core, x86: make LIST

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Date:	Mon, 28 Dec 2009 12:11:22 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH] core, x86: make LIST_POISON less deadly

Hi Linus,

On Sun, 20 Dec 2009 15:22:30 +0200 Avi Kivity <avi@...hat.com> wrote:
>
> From: Avi Kivity <avi@...ranet.com>
> 
> 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-undereferencable values.
> This is easy on x86_64 as the virtual address space is large and contains
> areas that cannot be mapped.
> 
> Other 64-bit architectures will likely find similar unmapped ranges.
> 
> [ingo: switch to 0xdead000000000000 as the unmapped area]
> [ingo: add comments, cleanup]
> [jaswinder: eliminate sparse warnings]
> 
> Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@...il.com>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Avi Kivity <avi@...hat.com>

The above fixed version of this patch has been in linux-next (via the tip
tree) for one year minus one day.

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au
http://www.canb.auug.org.au/~sfr/

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