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Date:   Thu, 20 Jun 2019 18:19:27 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Qian Cai <cai@lca.pw>
Cc:     akpm@linux-foundation.org, glider@google.com, cl@linux.com,
        penberg@kernel.org, rientjes@google.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next] slub: play init_on_free=1 well with SLAB_RED_ZONE
Message-ID: <201906201818.6C90BC875@keescook>
References: <1561058881-9814-1-git-send-email-cai@lca.pw>
 <201906201812.8B49A36@keescook>
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On Thu, Jun 20, 2019 at 06:14:33PM -0700, Kees Cook wrote:
> On Thu, Jun 20, 2019 at 03:28:01PM -0400, Qian Cai wrote:
> > diff --git a/mm/slub.c b/mm/slub.c
> > index a384228ff6d3..787971d4fa36 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -1437,7 +1437,7 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
> >  		do {
> >  			object = next;
> >  			next = get_freepointer(s, object);
> > -			memset(object, 0, s->size);
> > +			memset(object, 0, s->object_size);
> 
> I think this should be more dynamic -- we _do_ want to wipe all
> of object_size in the case where it's just alignment and padding
> adjustments. If redzones are enabled, let's remove that portion only.

(Sorry, I meant: all of object's "size", not object_size.)

-- 
Kees Cook