Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 31 Jul 2018 15:38:13 +0000
From:   Christopher Lameter <cl@linux.com>
To:     Dmitry Vyukov <dvyukov@google.com>
cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        vincenzo.frascino@arm.com, Alexander Potapenko <glider@google.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Dave Martin <dave.martin@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Ingo Molnar <mingo@kernel.org>,
        Paul Lawrence <paullawrence@google.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-sparse@vger.kernel.org,
        Linux Memory Management List <linux-mm@kvack.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Chintan Pandya <cpandya@codeaurora.org>,
        Jacob Bramley <Jacob.Bramley@arm.com>,
        Jann Horn <jannh@google.com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
        Lee Smith <Lee.Smith@arm.com>,
        Kostya Serebryany <kcc@google.com>,
        Mark Brand <markbrand@google.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
        Evgeniy Stepanov <eugenis@google.com>
Subject: Re: [PATCH v4 13/17] khwasan: add hooks implementation
In-Reply-To: <CACT4Y+Y=61VwwETQP3FwAN16ompSNJOCyDCG6Ew1Bm5f_Fe1Lw@mail.gmail.com>
Message-ID: <01000164f0fd5abc-df9ea911-9701-498c-adce-9f833e6df3ed-000000@email.amazonses.com>
References: <cover.1530018818.git.andreyknvl@google.com> <a2a93370d43ec85b02abaf8d007a15b464212221.1530018818.git.andreyknvl@google.com> <09cb5553-d84a-0e62-5174-315c14b88833@arm.com> <CAAeHK+yC3XRPoTByhH1QPrX45pG3QY_2Q4gz=dfDgxfzu1Fyfw@mail.gmail.com>
 <8240d4f9-c8df-cfe9-119d-6e933f8b13df@virtuozzo.com> <CACT4Y+Y=61VwwETQP3FwAN16ompSNJOCyDCG6Ew1Bm5f_Fe1Lw@mail.gmail.com>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Feedback-ID: 1.us-east-1.fQZZZ0Xtj2+TD7V5apTT/NrT6QKuPgzCT/IC7XYgDKI=:AmazonSES
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, 31 Jul 2018, Dmitry Vyukov wrote:

> > Actually you should do this for SLAB_TYPESAFE_BY_RCU slabs. Usually they are with ->ctors but there
> > are few without constructors.
> > We can't reinitialize or even retag them. The latter will definitely cause false-positive use-after-free reports.
>
> Somewhat offtopic, but I can't understand how SLAB_TYPESAFE_BY_RCU
> slabs can be useful without ctors or at least memset(0). Objects in
> such slabs need to be type-stable, but I can't understand how it's
> possible to establish type stability without a ctor... Are these bugs?
> Or I am missing something subtle? What would be a canonical usage of
> SLAB_TYPESAFE_BY_RCU slab without a ctor?

True that sounds fishy. Would someone post a list of SLAB_TYPESAFE_BY_RCU
slabs without ctors?