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

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Date:   Mon, 6 Mar 2017 10:28:42 -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 10:42 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Sun, 2017-03-05 at 21:38 -0800, Cong Wang wrote:
>
>> 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?
>
> What makes you think BH can't be disabled twice ?
>
> Look, I prefer being cautious here, no need to get another DCCP bug
> report later.

Hmm, I thought BH should have a local_bh_save() to save its context
but looking into its implementation it uses the preempt count to determine
if BH is disabled or not, unlikely hardirq's. Sorry for the noise.