From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
David Miller <davem@davemloft.net>,
Willem de Bruijn <willemb@google.com>,
Eric Dumazet <edumazet@google.com>,
Daniel Borkmann <daniel@iogearbox.net>,
jarno@ovn.org, philip.pettersson@gmail.com,
weongyo.linux@gmail.com, netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: net/packet: use-after-free in packet_rcv_fanout
Date: Thu, 9 Feb 2017 19:33:06 -0800 [thread overview]
Message-ID: <20170210033306.GA770@oracle.com> (raw)
In-Reply-To: <1486696765.7793.119.camel@edumazet-glaptop3.roam.corp.google.com>
On (02/09/17 19:19), Eric Dumazet wrote:
>
> More likely the bug is in fanout_add(), with a buggy sequence in error
> case, and not correct locking.
>
> kfree(po->rollover);
> po->rollover = NULL;
>
> Two cpus entering fanout_add() (using the same af_packet socket,
> syzkaller courtesy...) might both see po->fanout being NULL.
>
> Then they grab the mutex. Too late...
I'm not sure I follow- aiui the panic was in acceessing the
sk_receive_queue.lock in a socket that had been closed earlier. I think
the assumption is that rcu_read_lock_bh in __dev_queue_xmit (and
rcu_read_lock in dev_queue_xmit_nit?) should make sure that the nit
packet delivery can be done safely, and the synchronize_net in
packet_release() makes sure that the Tx paths are quiesced before freeing
the socket. What is the race-hole here? Does it have to do with the
_bh and softirq context, somehow?
--Sowmini
next prev parent reply other threads:[~2017-02-10 3:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-09 13:14 net/packet: use-after-free in packet_rcv_fanout Dmitry Vyukov
2017-02-09 15:12 ` Sowmini Varadhan
2017-02-09 15:17 ` Eric Dumazet
2017-02-10 1:24 ` Cong Wang
2017-02-10 3:19 ` Eric Dumazet
2017-02-10 3:23 ` Eric Dumazet
2017-02-10 17:49 ` Cong Wang
2017-02-10 17:59 ` Eric Dumazet
2017-02-10 18:02 ` Cong Wang
2017-02-10 18:15 ` Eric Dumazet
2017-02-10 18:02 ` Eric Dumazet
2017-02-10 18:34 ` Cong Wang
2017-02-10 3:33 ` Sowmini Varadhan [this message]
2017-02-10 4:18 ` Eric Dumazet
2017-02-10 18:00 ` Cong Wang
2017-02-10 19:16 ` Sowmini Varadhan
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