From: Dmitry Vyukov <dvyukov@google.com>
Subject: Re: SLAB_TYPESAFE_BY_RCU without constructors (was Re: [PATCH v4
 13/17] khwasan: add hooks implementation)
Date: Wed, 1 Aug 2018 15:52:40 +0200
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        "Theodore Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.com>,
        linux-ext4@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
        David Miller <davem@davemloft.net>,
        NetFilter <netfilter-devel@vger.kernel.org>,
        coreteam@netfilter.org,
        Network Development <netdev@vger.kernel.org>,
        Gerrit Renker <gerrit@erg.abdn.ac.uk>, dccp@vger.kernel.org,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Dave Airlie <airlied@linux.ie>,
        intel-gfx <intel-gfx@lists.freedeskt
To: Florian Westphal <fw@strlen.de>
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On Wed, Aug 1, 2018 at 3:46 PM, Florian Westphal <fw@strlen.de> wrote:
> Dmitry Vyukov <dvyukov@google.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.