netdev - Re: [PATCH net] sctp: disable BH in sctp_for_each

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Date:   Sat, 10 Jun 2017 16:18:42 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     lucien.xin@...il.com
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        marcelo.leitner@...il.com, nhorman@...driver.com
Subject: Re: [PATCH net] sctp: disable BH in sctp_for_each_endpoint

From: Xin Long <lucien.xin@...il.com>
Date: Sat, 10 Jun 2017 14:48:14 +0800

> Now sctp holds read_lock when foreach sctp_ep_hashtable without disabling
> BH. If CPU schedules to another thread A at this moment, the thread A may
> be trying to hold the write_lock with disabling BH.
> 
> As BH is disabled and CPU cannot schedule back to the thread holding the
> read_lock, while the thread A keeps waiting for the read_lock. A dead
> lock would be triggered by this.
> 
> This patch is to fix this dead lock by calling read_lock_bh instead to
> disable BH when holding the read_lock in sctp_for_each_endpoint.
> 
> Fixes: 626d16f50f39 ("sctp: export some apis or variables for sctp_diag and reuse some for proc")
> Reported-by: Xiumei Mu <xmu@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Applied and queued up for -stable, thanks.