netdev - Re: [PATCH net] ppp: Fix a scheduling-while-atomic bug in del

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Message-Id: <20170731.215948.1332618179008379005.davem@davemloft.net>
Date:   Mon, 31 Jul 2017 21:59:48 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     gfree.wind@....163.com
Cc:     xeb@...l.ru, netdev@...r.kernel.org
Subject: Re: [PATCH net] ppp: Fix a scheduling-while-atomic bug in del_chan

From: gfree.wind@....163.com
Date: Mon, 31 Jul 2017 18:07:38 +0800

> From: Gao Feng <gfree.wind@....163.com>
> 
> The PPTP set the pptp_sock_destruct as the sock's sk_destruct, it would
> trigger this bug when __sk_free is invoked in atomic context, because of
> the call path pptp_sock_destruct->del_chan->synchronize_rcu.
> 
> Now move the synchronize_rcu to pptp_release from del_chan. This is the
> only one case which would free the sock and need the synchronize_rcu.
> 
> The following is the panic I met with kernel 3.3.8, but this issue should
> exist in current kernel too according to the codes.
 ...
> Signed-off-by: Gao Feng <gfree.wind@....163.com>

Applied, thanks.