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[73.169.115.106]) by smtp.googlemail.com with ESMTPSA id f62sm471162pfg.74.2019.10.02.15.33.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 02 Oct 2019 15:33:41 -0700 (PDT) Subject: Re: [PATCH net v2] ipv6: Handle race in addrconf_dad_work To: Eric Dumazet , David Ahern , davem@davemloft.net, jakub.kicinski@netronome.com Cc: netdev@vger.kernel.org, rajendra.dendukuri@broadcom.com References: <20191001032834.5330-1-dsahern@kernel.org> <1ab3e0d0-fb37-d367-fd5f-c6b3262b6583@gmail.com> <18c18892-3f1c-6eb8-abbb-00fd6c9c64d3@gmail.com> <146a2f8a-8ee9-65f3-1013-ef60a96aa27b@gmail.com> <8d13d82c-6a91-1434-f1af-a2f39ecadbfb@gmail.com> <3dc05826-4661-8a8e-0c15-1a711ec84d07@gmail.com> From: David Ahern Message-ID: <45e62fee-1580-4c5d-7cac-5f0db935fa9e@gmail.com> Date: Wed, 2 Oct 2019 16:33:40 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <3dc05826-4661-8a8e-0c15-1a711ec84d07@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 10/2/19 4:21 PM, Eric Dumazet wrote: > o syzbot this time, but complete lack of connectivity on some of my test hosts. > > Incoming IPv6 packets go to ip6_forward() (!!!) and are dropped there. what does 'ip -6 addr sh' show when it is in this state? Any idea of the order of events? > > There seems to be something missing. > > ifp->state stays at INET6_IFADDR_STATE_PREDAD instead of INET6_IFADDR_STATE_DAD > My original suggestion to Rajendra was this: diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 6a576ff92c39..5ec795086432 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -4032,6 +4032,12 @@ static void addrconf_dad_work(struct work_struct *w) rtnl_lock(); + /* device was taken down before this delayed work function + * could be canceled + */ + if (!(idev->dev->flags & IFF_UP)) + goto out; + spin_lock_bh(&ifp->lock); if (ifp->state == INET6_IFADDR_STATE_PREDAD) { action = DAD_BEGIN; I flipped to IF_READY based on addrconf_ifdown and idev checks seeming more appropriate.