netdev - Re: [PATCH net V2] tuntap: correctly wake up process during uninit

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Message-Id: <20160520.193806.543505636945844730.davem@davemloft.net>
Date:	Fri, 20 May 2016 19:38:06 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	jasowang@...hat.com
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	edumazet@...gle.com, xii@...gle.com, mst@...hat.com
Subject: Re: [PATCH net V2] tuntap: correctly wake up process during uninit

From: Jason Wang <jasowang@...hat.com>
Date: Thu, 19 May 2016 13:36:51 +0800

> We used to check dev->reg_state against NETREG_REGISTERED after each
> time we are woke up. But after commit 9e641bdcfa4e ("net-tun:
> restructure tun_do_read for better sleep/wakeup efficiency"), it uses
> skb_recv_datagram() which does not check dev->reg_state. This will
> result if we delete a tun/tap device after a process is blocked in the
> reading. The device will wait for the reference count which was held
> by that process for ever.
> 
> Fixes this by using RCV_SHUTDOWN which will be checked during
> sk_recv_datagram() before trying to wake up the process during uninit.
> 
> Fixes: 9e641bdcfa4e ("net-tun: restructure tun_do_read for better
> sleep/wakeup efficiency")
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Xi Wang <xii@...gle.com>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
> - The patch is needed for -stable.
> - Changes from v1: remove unnecessary NETREG_REGISTERED check in tun_do_read()

Applied and queued up for -stable.