linux-kernel - Re: [PATCH v4 13/17] khwasan: add hooks implementation

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Message-ID: <CACT4Y+b6_d6b5Q4oScXuoXhsnkJPG+UZ1QxqPPGuM4_aU3n4mA@mail.gmail.com>
Date:   Tue, 31 Jul 2018 18:03:16 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        vincenzo.frascino@....com, Alexander Potapenko <glider@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Dave Martin <dave.martin@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Ingo Molnar <mingo@...nel.org>,
        Paul Lawrence <paullawrence@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-sparse@...r.kernel.org,
        Linux Memory Management List <linux-mm@...ck.org>,
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        Lee Smith <Lee.Smith@....com>,
        Kostya Serebryany <kcc@...gle.com>,
        Mark Brand <markbrand@...gle.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Evgeniy Stepanov <eugenis@...gle.com>
Subject: Re: [PATCH v4 13/17] khwasan: add hooks implementation

On Tue, Jul 31, 2018 at 5:38 PM, Christopher Lameter <cl@...ux.com> wrote:
> 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?

https://elixir.bootlin.com/linux/latest/source/fs/jbd2/journal.c#L2395
https://elixir.bootlin.com/linux/latest/source/fs/kernfs/mount.c#L415
https://elixir.bootlin.com/linux/latest/source/net/netfilter/nf_conntrack_core.c#L2065
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/i915/i915_gem.c#L5501
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/i915/selftests/mock_gem_device.c#L212
https://elixir.bootlin.com/linux/latest/source/drivers/staging/lustre/lustre/ldlm/ldlm_lockd.c#L1131

Also these in proto structs:
https://elixir.bootlin.com/linux/latest/source/net/dccp/ipv4.c#L959
https://elixir.bootlin.com/linux/latest/source/net/dccp/ipv6.c#L1048
https://elixir.bootlin.com/linux/latest/source/net/ipv4/tcp_ipv4.c#L2461
https://elixir.bootlin.com/linux/latest/source/net/ipv6/tcp_ipv6.c#L1980
https://elixir.bootlin.com/linux/latest/source/net/llc/af_llc.c#L145
https://elixir.bootlin.com/linux/latest/source/net/smc/af_smc.c#L105

They later created in net/core/sock.c without ctor.