netdev - Re: [PATCH net] dccp: fix use-after-free in dccp_feat_activate

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Date:   Sun, 5 Mar 2017 21:38:07 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Gerrit Renker <gerrit@....abdn.ac.uk>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] dccp: fix use-after-free in dccp_feat_activate_values

On Sun, Mar 5, 2017 at 10:52 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> --- a/net/dccp/minisocks.c
> +++ b/net/dccp/minisocks.c
> @@ -142,6 +142,13 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
>         struct dccp_request_sock *dreq = dccp_rsk(req);
>         bool own_req;
>
> +       /* TCP/DCCP listeners became lockless.
> +        * DCCP stores complex state in its request_sock, so we need
> +        * a protection for them, now this code runs without being protected
> +        * by the parent (listener) lock.
> +        */
> +       spin_lock_bh(&dreq->dreq_lock);
> +

Do you really want to disable BH again here?

dccp_check_req() should be always called on RX path where BH
is already disabled and BH can't be disabled twice?