| Message ID | 1480439696-21818-1-git-send-email-xiyou.wangcong@gmail.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
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 -- Richard Guy Briggs <rgb@redhat.com> Kernel Security Engineering, Base Operating Systems, Red Hat Remote, Ottawa, Canada Voice: +1.647.777.2635, Internal: (81) 32635
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.
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.
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 = {
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(-)