linux-kernel - Re: SLAB_TYPESAFE_BY_RCU without constructors (was Re: [PATCH v4 13/17] khwasan: add hooks implementation)

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Message-ID: <CACT4Y+ay6+UTLMr4K_RTTubjzpGZXe2n7T8Q=kC=Q1baHshkHQ@mail.gmail.com>
Date:   Wed, 1 Aug 2018 15:52:40 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Florian Westphal <fw@...len.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "Theodore Ts'o" <tytso@....edu>, Jan Kara <jack@...e.com>,
        linux-ext4@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        David Miller <davem@...emloft.net>,
        NetFilter <netfilter-devel@...r.kernel.org>,
        coreteam@...filter.org,
        Network Development <netdev@...r.kernel.org>,
        Gerrit Renker <gerrit@....abdn.ac.uk>, dccp@...r.kernel.org,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Dave Airlie <airlied@...ux.ie>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        DRI <dri-devel@...ts.freedesktop.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: SLAB_TYPESAFE_BY_RCU without constructors (was Re: [PATCH v4
 13/17] khwasan: add hooks implementation)

On Wed, Aug 1, 2018 at 3:46 PM, Florian Westphal <fw@...len.de> wrote:
> Dmitry Vyukov <dvyukov@...gle.com> wrote:
>> If that scenario is possible that a fix would be to make
>
> Looks possible.
>
>> __nf_conntrack_find_get ever return NULL iff it got NULL from
>> ____nf_conntrack_find (not if any of the checks has failed).
>
> I don't see why we need to restart on nf_ct_is_dying(), but other
> than that this seems ok.

Because it can be a wrong entry dying. When we check dying, we don't
yet know if we are looking at the right entry or not. If we
successfully acquire a reference, then recheck nf_ct_key_equal and
_then_ check dying, then we don't need to restart on dying. But with
the current check order, we need to restart on dying too.