Le jeudi 18 novembre 2010 Ã 10:43 +0100, Eric Dumazet a Ãcrit :
> Le jeudi 18 novembre 2010 Ã 10:33 +0100, Eric Dumazet a Ãcrit :
> >
> >
> >
> > Hmm, sorry but this wont work.
> >
> > > diff -Narup linux-2.6-next/drivers/s390/net/lcs.c linux-2.6-next-new/drivers/s390/net/lcs.c
> > > --- linux-2.6-next/drivers/s390/net/lcs.c 2010-11-17 11:38:25.000000000 +0530
> > > +++ linux-2.6-next-new/drivers/s390/net/lcs.c 2010-11-18 11:59:46.000000000 +0530
> > > @@ -1269,10 +1269,10 @@ lcs_register_mc_addresses(void *data)
> > > in4_dev = in_dev_get(card->dev);
> > > if (in4_dev == NULL)
> > > goto out;
> > > - read_lock(&in4_dev->mc_list_lock);
> > > + rcu_read_lock();
> >
> > If you use rcu_read_lock(), then you also need to
> > use the rcu list iterators in lcs_remove_mc_addresses() and
> > lcs_set_mc_addresses()
> >
> > Then, its strange this driver is not protected by RTNL at this stage.
> >
> > Ah yes, it uses a kthread from its ndo_set_multicast_list() handler.
> >
> > This seems not safe at all.
Actually this raises an interesting case for bonding as well.
Before my RCU conversion __bond_resend_igmp_join_requests() was unsafe.
For net-next-2.6, it is now safe (RCU is held), but needs a cleanup
patch to avoid sparse errors.
Thanks
[PATCH net-2.6] bonding: fix a race in IGMP handling
RCU conversion in IGMP code done in net-next-2.6 raised a race in
__bond_resend_igmp_join_requests().
It iterates in_dev->mc_list without appropriate protection (RTNL, or
read_lock on in_dev->mc_list_lock).
Another cpu might delete an entry while we use it and trigger a fault.
Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Jay Vosburgh <fubar@xxxxxxxxxx>
---
drivers/net/bonding/bond_main.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index bdb68a6..71a1697 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -878,8 +878,10 @@ static void __bond_resend_igmp_join_requests(struct net_device *dev)
rcu_read_lock();
in_dev = __in_dev_get_rcu(dev);
if (in_dev) {
+ read_lock(&in_dev->mc_list_lock);
for (im = in_dev->mc_list; im; im = im->next)
ip_mc_rejoin_group(im);
+ read_unlock(&in_dev->mc_list_lock);
}
rcu_read_unlock();
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