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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id b26sm680142pfo.129.2019.06.20.18.19.28 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 20 Jun 2019 18:19:28 -0700 (PDT) Date: Thu, 20 Jun 2019 18:19:27 -0700 From: Kees Cook To: Qian Cai 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201906201812.8B49A36@keescook> X-Bogosity: Ham, tests=bogofilter, spamicity=0.005145, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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