On Fri, 2013-07-26 at 13:47 -0700, Greg Kroah-Hartman wrote: > 3.10-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Eric Dumazet <[email protected]> > > [ Upstream commit 3e3aac497513c669e1c62c71e1d552ea85c1d974 ] > > egress_priority_map[] hash table updates are protected by rtnl, > and we never remove elements until device is dismantled. > > We have to make sure that before inserting an new element in hash table, > all its fields are committed to memory or else another cpu could > find corrupt values and crash. > > Signed-off-by: Eric Dumazet <[email protected]> > Cc: Patrick McHardy <[email protected]> > Signed-off-by: David S. Miller <[email protected]> > Signed-off-by: Greg Kroah-Hartman <[email protected]> > --- > net/8021q/vlan_dev.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > --- a/net/8021q/vlan_dev.c > +++ b/net/8021q/vlan_dev.c > @@ -73,6 +73,8 @@ vlan_dev_get_egress_qos_mask(struct net_ > { > struct vlan_priority_tci_mapping *mp; > > + smp_rmb(); /* coupled with smp_wmb() in vlan_dev_set_egress_priority() > */ > + > mp = vlan_dev_priv(dev)->egress_priority_map[(skb->priority & 0xF)];
This barrier is the wrong type in the wrong place; there should be a
smp_read_barrier_depends() *after* reading the pointer from
egress_priority_map, and after reading each next pointer.
(In practice, I think this error is harmless except on Alpha. So the
patch is worth applying anyway.)
Ben.
> while (mp) {
> if (mp->priority == skb->priority) {
> @@ -249,6 +251,11 @@ int vlan_dev_set_egress_priority(const s
> np->next = mp;
> np->priority = skb_prio;
> np->vlan_qos = vlan_qos;
> + /* Before inserting this element in hash table, make sure all its fields
> + * are committed to memory.
> + * coupled with smp_rmb() in vlan_dev_get_egress_qos_mask()
> + */
> + smp_wmb();
> vlan->egress_priority_map[skb_prio & 0xF] = np;
> if (vlan_qos)
> vlan->nr_egress_mappings++;
--
Ben Hutchings
Once a job is fouled up, anything done to improve it makes it worse.
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