netdev - Re: [Patch net-next] audit: remove useless synchronize

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Message-ID: <20161130091643.GA32562@madcap2.tricolour.ca>
Date:   Wed, 30 Nov 2016 04:16:43 -0500
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, linux-audit@...hat.com, pmoore@...hat.com
Subject: Re: [Patch net-next] audit: remove useless synchronize_net()

On 2016-11-29 09:14, Cong Wang wrote:
> netlink kernel socket is protected by refcount, not RCU.
> Its rcv path is neither protected by RCU. So the synchronize_net()
> is just pointless.

If I understand correctly, xfrm_user_net_exit() usage of
RCU_INIT_POINTER() and synchronize_net() is similarly pointless?  Also
net/phonet/socket.c?  I probably modelled things based on the former...

> Cc: Richard Guy Briggs <rgb@...hat.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---
>  kernel/audit.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 92c463d..67b9fbd8 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1172,9 +1172,8 @@ static void __net_exit audit_net_exit(struct net *net)
>  		audit_sock = NULL;
>  	}
>  
> -	RCU_INIT_POINTER(aunet->nlsk, NULL);
> -	synchronize_net();
>  	netlink_kernel_release(sock);
> +	aunet->nlsk = NULL;
>  }
>  
>  static struct pernet_operations audit_net_ops __net_initdata = {
> -- 
> 2.1.0
> 

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Kernel Security Engineering, Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635