linux-kernel - Re: [PATCH] mm: Add additional consistency check

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Date:   Tue, 4 Apr 2017 17:58:56 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: Add additional consistency check

On Tue 04-04-17 08:46:02, Kees Cook wrote:
> On Tue, Apr 4, 2017 at 8:16 AM, Michal Hocko <mhocko@...nel.org> wrote:
> > On Tue 04-04-17 10:07:23, Cristopher Lameter wrote:
> >> On Tue, 4 Apr 2017, Michal Hocko wrote:
> >>
> >> > NAK without a proper changelog. Seriously, we do not blindly apply
> >> > changes from other projects without a deep understanding of all
> >> > consequences.
> >>
> >> Functionalitywise this is trivial. A page must be a slab page in order to
> >> be able to determine the slab cache of an object. Its definitely not ok if
> >> the page is not a slab page.
> >
> > Yes, but we do not have to blow the kernel, right? Why cannot we simply
> > leak that memory?
> 
> I can put this behind CHECK_DATA_CORRUPTION() instead of BUG(), which
> allows the system builder to choose between WARN and BUG. Some people
> absolutely want the kernel to BUG on data corruption as it could be an
> attack.

CHECK_DATA_CORRUPTION sounds as better fit to me. This would, however
require to handle the potenial corruption by returning and leaking the
memory.

-- 
Michal Hocko
SUSE Labs