* [Patch net-next] audit: remove useless synchronize_net()
@ 2016-11-29 17:14 Cong Wang
2016-11-30 9:16 ` Richard Guy Briggs
2016-12-01 16:29 ` David Miller
0 siblings, 2 replies; 4+ messages in thread
From: Cong Wang @ 2016-11-29 17:14 UTC (permalink / raw)
To: netdev; +Cc: Cong Wang, Richard Guy Briggs
netlink kernel socket is protected by refcount, not RCU.
Its rcv path is neither protected by RCU. So the synchronize_net()
is just pointless.
Cc: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.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
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [Patch net-next] audit: remove useless synchronize_net()
2016-11-29 17:14 [Patch net-next] audit: remove useless synchronize_net() Cong Wang
@ 2016-11-30 9:16 ` Richard Guy Briggs
2016-11-30 17:20 ` Cong Wang
2016-12-01 16:29 ` David Miller
1 sibling, 1 reply; 4+ messages in thread
From: Richard Guy Briggs @ 2016-11-30 9:16 UTC (permalink / raw)
To: Cong Wang; +Cc: netdev, linux-audit, pmoore
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@redhat.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [Patch net-next] audit: remove useless synchronize_net()
2016-11-30 9:16 ` Richard Guy Briggs
@ 2016-11-30 17:20 ` Cong Wang
0 siblings, 0 replies; 4+ messages in thread
From: Cong Wang @ 2016-11-30 17:20 UTC (permalink / raw)
To: Richard Guy Briggs
Cc: Linux Kernel Network Developers, linux-audit, Paul Moore
On Wed, Nov 30, 2016 at 1:16 AM, Richard Guy Briggs <rgb@redhat.com> wrote:
> 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...
Possibly, but xfrm case is slightly different, it has two copies of the pointer
to the netlink socket, also it uses exit_batch(). I need to double check.
Take a look at better examples, fib_front, genetlink, rtnetlink.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Patch net-next] audit: remove useless synchronize_net()
2016-11-29 17:14 [Patch net-next] audit: remove useless synchronize_net() Cong Wang
2016-11-30 9:16 ` Richard Guy Briggs
@ 2016-12-01 16:29 ` David Miller
1 sibling, 0 replies; 4+ messages in thread
From: David Miller @ 2016-12-01 16:29 UTC (permalink / raw)
To: xiyou.wangcong; +Cc: netdev, rgb
From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Tue, 29 Nov 2016 09:14:56 -0800
> netlink kernel socket is protected by refcount, not RCU.
> Its rcv path is neither protected by RCU. So the synchronize_net()
> is just pointless.
>
> Cc: Richard Guy Briggs <rgb@redhat.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Applied, thanks.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2016-11-29 17:14 [Patch net-next] audit: remove useless synchronize_net() Cong Wang
2016-11-30 9:16 ` Richard Guy Briggs
2016-11-30 17:20 ` Cong Wang
2016-12-01 16:29 ` David Miller
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