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;
MIME-Version: 1.0
In-Reply-To: <20180801134628.ueyzwg2gszrvk2hc@breakpoint.cc>
References: <e3b48104-3efb-1896-0d46-792419f49a75@virtuozzo.com>
 <01000164f169bc6b-c73a8353-d7d9-47ec-a782-90aadcb86bfb-000000@email.amazonses.com>
 <CA+55aFzHR1+YbDee6Cduo6YXHO9LKmLN1wP=MVzbP41nxUb5=g@mail.gmail.com>
 <CA+55aFzYLgyNp1jsqsvUOjwZdO_1Piqj=iB=rzDShjScdNtkbg@mail.gmail.com>
 <CACT4Y+aYZumcc-Od5T1AnP4mwn8-FaWfxvfb93MnNwQPqG8TDw@mail.gmail.com>
 <CACT4Y+ZkgqDT77dshHg+hBtc9YPW-eZ8wVQA9LTDQ6q_y99oiQ@mail.gmail.com>
 <20180801103537.d36t3snzulyuge7g@breakpoint.cc> <CACT4Y+aHWpgDZygXv=smWwdVMWfjpedyajuVvvLDGMK-wFD5Lw@mail.gmail.com>
 <20180801114048.ufkr7zwmir7ps3vl@breakpoint.cc> <CACT4Y+ZNnYojj0x_DoUxeUREaEgzcf3UG=UW_P4vzsnZNjjgMQ@mail.gmail.com>
 <20180801134628.ueyzwg2gszrvk2hc@breakpoint.cc>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Wed, 1 Aug 2018 15:52:40 +0200
Message-ID: <CACT4Y+ay6+UTLMr4K_RTTubjzpGZXe2n7T8Q=kC=Q1baHshkHQ@mail.gmail.com>
Subject: Re: SLAB_TYPESAFE_BY_RCU without constructors (was Re: [PATCH v4
 13/17] khwasan: add hooks implementation)
To:     Florian Westphal <fw@strlen.de>
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.freedesktop.org>,
        DRI <dri-devel@lists.freedesktop.org>,
        Eric Dumazet <edumazet@google.com>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Ursula Braun <ubraun@linux.ibm.com>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        Andrey Konovalov <andreyknvl@google.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.