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Date: Wed, 10 Jan 2018 12:14:07 -0800
From: Kees Cook <keescook@...omium.org>
To: Christopher Lameter <cl@...ux.com>
Cc: LKML <linux-kernel@...r.kernel.org>, David Windsor <dave@...lcore.net>, 
	Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, 
	Joonsoo Kim <iamjoonsoo.kim@....com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Laura Abbott <labbott@...hat.com>, Ingo Molnar <mingo@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Linux-MM <linux-mm@...ck.org>, linux-xfs@...r.kernel.org, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Andy Lutomirski <luto@...nel.org>, Christoph Hellwig <hch@...radead.org>, 
	"David S. Miller" <davem@...emloft.net>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, Christian Borntraeger <borntraeger@...ibm.com>, 
	Christoffer Dall <christoffer.dall@...aro.org>, Dave Kleikamp <dave.kleikamp@...cle.com>, 
	Jan Kara <jack@...e.cz>, Luis de Bethencourt <luisbg@...nel.org>, Marc Zyngier <marc.zyngier@....com>, 
	Rik van Riel <riel@...hat.com>, Matthew Garrett <mjg59@...gle.com>, 
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>, 
	Network Development <netdev@...r.kernel.org>, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 05/36] usercopy: WARN() on slab cache usercopy region violations

On Wed, Jan 10, 2018 at 10:31 AM, Christopher Lameter <cl@...ux.com> wrote:
> On Tue, 9 Jan 2018, Kees Cook wrote:
>
>> @@ -3823,11 +3825,9 @@ int __check_heap_object(const void *ptr, unsigned long n, struct page *page,
>
> Could we do the check in mm_slab_common.c for all allocators and just have
> a small function in each allocators that give you the metadata needed for
> the object?

That could be done, but there would still need to be some
implementation-specific checks in the per-implementation side (e.g.
red-zone, etc). I'll work up a patch and see if it's less ugly than
what I've currently got. :)

>> + * carefully audit the whitelist range).
>> + */
>>  int report_usercopy(const char *name, const char *detail, bool to_user,
>>                   unsigned long offset, unsigned long len)
>>  {
>
> Should this not be added earlier?

This seemed like the best place to add this since it's where the WARN
is being added, so it's a bit more help for anyone looking at the
code.

-Kees

-- 
Kees Cook
Pixel Security

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