netdev - Re: [PATCH net 1/3] bonding: access curr_active_slave with rtnl

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Date:   Sat, 10 Dec 2022 20:28:20 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     netdev@...r.kernel.org, Jay Vosburgh <j.vosburgh@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Toppins <jtoppins@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>, liali <liali@...hat.com>
Subject: Re: [PATCH net 1/3] bonding: access curr_active_slave with
 rtnl_dereference

On Sat, Dec 10, 2022 at 12:58:59AM +0100, Eric Dumazet wrote:
> On Fri, Dec 9, 2022 at 11:13 AM Hangbin Liu <liuhangbin@...il.com> wrote:
> >
> > Looks commit 4740d6382790 ("bonding: add proper __rcu annotation for
> > curr_active_slave") missed rtnl_dereference for curr_active_slave
> > in bond_miimon_commit().
> >
> > Fixes: 4740d6382790 ("bonding: add proper __rcu annotation for curr_active_slave")
> 
> 
> > Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> > ---
> >  drivers/net/bonding/bond_main.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> > index b9a882f182d2..2b6cc4dbb70e 100644
> > --- a/drivers/net/bonding/bond_main.c
> > +++ b/drivers/net/bonding/bond_main.c
> > @@ -2689,7 +2689,7 @@ static void bond_miimon_commit(struct bonding *bond)
> >
> >                         bond_miimon_link_change(bond, slave, BOND_LINK_UP);
> >
> > -                       if (!bond->curr_active_slave || slave == primary)
> > +                       if (!rtnl_dereference(bond->curr_active_slave) || slave == primary)
> 
> We do not dereference the pointer here.
> 
> If this is fixing a sparse issue, then use the correct RCU helper for this.
> 
> ( rcu_access_pointer())

Hmm... I saw in 4740d6382790 ("bonding: add proper __rcu annotation for
 curr_active_slave") there are also some dereference like that. Should I also
fix them at the same time? e.g.

@@ -2607,8 +2612,8 @@ static void bond_ab_arp_commit(struct bonding *bond)

                case BOND_LINK_UP:
                        trans_start = dev_trans_start(slave->dev);
-                       if (bond->curr_active_slave != slave ||
-                           (!bond->curr_active_slave &&
+                       if (rtnl_dereference(bond->curr_active_slave) != slave ||
+                           (!rtnl_dereference(bond->curr_active_slave) &&

Thanks
Hangbin