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

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Date:   Tue, 4 Apr 2017 13:30:23 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: Add additional consistency check

On Fri 31-03-17 09:40:28, Kees Cook wrote:
> As found in PaX, this adds a cheap check on heap consistency, just to
> notice if things have gotten corrupted in the page lookup.
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

NAK without a proper changelog. Seriously, we do not blindly apply
changes from other projects without a deep understanding of all
consequences.

> ---
>  mm/slab.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/slab.h b/mm/slab.h
> index 65e7c3fcac72..64447640b70c 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -384,6 +384,7 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
>  		return s;
>  
>  	page = virt_to_head_page(x);
> +	BUG_ON(!PageSlab(page));
>  	cachep = page->slab_cache;
>  	if (slab_equal_or_root(cachep, s))
>  		return cachep;
> -- 
> 2.7.4
> 
> 
> -- 
> Kees Cook
> Pixel Security
> 
> --
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-- 
Michal Hocko
SUSE Labs