Re: [PATCHv4 net 1/3] bonding: move IPsec deletion to bond_ipsec_free_sa

Hangbin Liu
2025-03-06T10:02:34Z

On Thu, Mar 06, 2025 at 09:37:53AM +0000, Hangbin Liu wrote:
> >
> > The reason the mutex was added (instead of the spinlock used before)
> > was exactly because the add and free offload operations could sleep.
> >
> > > With your reply, I also checked the xdo_dev_state_add() in
> > > bond_ipsec_add_sa_all(), which may also sleep, e.g.
> > > mlx5e_xfrm_add_state(),
> > >
> > > If we unlock the spin lock, then the race came back again.
> > >
> > > Any idea about this?
> >
> > The race is between bond_ipsec_del_sa_all and bond_ipsec_del_sa (plus
> > bond_ipsec_free_sa). The issue is that when bond_ipsec_del_sa_all
> > releases x->lock, bond_ipsec_del_sa can immediately be called, followed
> > by bond_ipsec_free_sa.
> > Maybe dropping x->lock after setting real_dev to NULL? I checked,
> > real_dev is not used anywhere on the free calls, I think. I have
> > another series refactoring things around real_dev, I hope to be able to
> > send it soon.
> >
> > Here's a sketch of this idea:
> >
> > --- a/drivers/net/bonding/bond_main.c
> > +++ b/drivers/net/bonding/bond_main.c
> > @@ -613,8 +613,11 @@ static void bond_ipsec_del_sa_all(struct bonding
> > *bond)
> >
> > mutex_lock(&bond->ipsec_lock);
> > list_for_each_entry(ipsec, &bond->ipsec_list, list) {
> > - if (!ipsec->xs->xso.real_dev)
> > + spin_lock(&ipsec->x->lock);
> > + if (!ipsec->xs->xso.real_dev) {
> > + spin_unlock(&ipsec->x->lock);
> > continue;
> > + }
> >
> > if (!real_dev->xfrmdev_ops ||
> > !real_dev->xfrmdev_ops->xdo_dev_state_delete ||
> > @@ -622,12 +625,16 @@ static void bond_ipsec_del_sa_all(struct bonding
> > *bond)
> > slave_warn(bond_dev, real_dev,
> > "%s: no slave
> > xdo_dev_state_delete\n",
> > __func__);
> > - } else {
> > - real_dev->xfrmdev_ops-
> > >xdo_dev_state_delete(real_dev, ipsec->xs);
> > - if (real_dev->xfrmdev_ops->xdo_dev_state_free)
> > - real_dev->xfrmdev_ops-
> > >xdo_dev_state_free(ipsec->xs);
> > - ipsec->xs->xso.real_dev = NULL;
> > + spin_unlock(&ipsec->x->lock);
> > + continue;
> > }
> > +
> > + real_dev->xfrmdev_ops->xdo_dev_state_delete(real_dev,
> > ipsec->xs);
> > + ipsec->xs->xso.real_dev = NULL;
>
> Set xs->xso.real_dev = NULL is a good idea. As we will break
> in bond_ipsec_del_sa()/bond_ipsec_free_sa() when there is no
> xs->xso.real_dev.
>
> For bond_ipsec_add_sa_all(), I will move the xso.real_dev = real_dev
> after .xdo_dev_state_add() in case the following situation.
>
> bond_ipsec_add_sa_all()
> spin_unlock(&ipsec->x->lock);
> ipsec->xs->xso.real_dev = real_dev;
> __xfrm_state_delete x->state = DEAD
> - bond_ipsec_del_sa()
> - .xdo_dev_state_delete()
> .xdo_dev_state_add()

Hmm, do we still need to the spin_lock in bond_ipsec_add_sa_all()? With
xs->xso.real_dev = NULL after bond_ipsec_del_sa_all(), it looks there is
no need the spin_lock in bond_ipsec_add_sa_all(). e.g.

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 04b677d0c45b..3ada51c63207 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -537,15 +537,27 @@ static void bond_ipsec_add_sa_all(struct bonding *bond)
}

list_for_each_entry(ipsec, &bond->ipsec_list, list) {
+ spin_lock_bh(&ipsec->xs->lock);
+ /* Skip dead xfrm states, they'll be freed later. */
+ if (ipsec->xs->km.state == XFRM_STATE_DEAD) {
+ spin_unlock_bh(&ipsec->xs->lock);
+ continue;
+ }
+
/* If new state is added before ipsec_lock acquired */
- if (ipsec->xs->xso.real_dev == real_dev)
+ if (ipsec->xs->xso.real_dev == real_dev) {
+ spin_unlock_bh(&ipsec->xs->lock);
continue;
+ }

- ipsec->xs->xso.real_dev = real_dev;
if (real_dev->xfrmdev_ops->xdo_dev_state_add(ipsec->xs, NULL)) {
slave_warn(bond_dev, real_dev, "%s: failed to add SA\n", __func__);
ipsec->xs->xso.real_dev = NULL;
}
+ /* Set real_dev after .xdo_dev_state_add in case
+ * __xfrm_state_delete() is called in parallel
+ */
+ ipsec->xs->xso.real_dev = real_dev;
}

The spin_lock here seems useless now. What do you think?

Thanks
Hangbin