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

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Message-ID: <20170418064124.GA22360@dhcp22.suse.cz>
Date:   Tue, 18 Apr 2017 08:41:25 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Christoph Lameter <cl@...ux.com>
Cc:     Kees Cook <keescook@...omium.org>,
        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 Mon 17-04-17 10:22:29, Cristopher Lameter wrote:
> On Tue, 11 Apr 2017, Michal Hocko wrote:
> 
> > On Tue 11-04-17 13:59:44, Cristopher Lameter wrote:
> > > On Tue, 11 Apr 2017, Michal Hocko wrote:
> > >
> > > > I didn't say anything like that. Hence the proposed patch which still
> > > > needs some more thinking and evaluation.
> > >
> > > This patch does not even affect kfree().
> >
> > Ehm? Are we even talking about the same thing? The whole discussion was
> > to catch invalid pointers to _kfree_ and why BUG* is not the best way to
> > handle that.
> 
> The patch does not do that. See my review. Invalid points to kfree are
> already caught with a bug on. See kfree in mm/slub.c

Are you even reading those emails? First of all we are talking about
slab here. Secondly I've already pointed out that the BUG_ON(!PageSlab)
in kmem_freepages is already too late because we do operate on a
potential garbage from invalid page...
-- 
Michal Hocko
SUSE Labs