Re: [PATCHv3 net 1/3] bonding: move IPsec deletion to bond_ipsec_free_sa

Hangbin Liu
2025-02-28T02:20:37Z

On Thu, Feb 27, 2025 at 03:31:01PM +0200, Nikolay Aleksandrov wrote:
> >> One more thing - note I'm not an xfrm expert by far but it seems to me here you have
> >> to also call xdo_dev_state_free() with the old active slave dev otherwise that will
> >> never get called with the original real_dev after the switch to a new
> >> active slave (or more accurately it might if the GC runs between the switching
> >> but it is a race), care must be taken wrt sequence of events because the XFRM
> >
> > Can we just call xs->xso.real_dev->xfrmdev_ops->xdo_dev_state_free(xs)
> > no matter xs->xso.real_dev == real_dev or not? I'm afraid calling
> > xdo_dev_state_free() every where may make us lot more easily.
> >
>
> You'd have to check all drivers that implement the callback to answer that and even then
> I'd stick to the canonical way of how it's done in xfrm and make the bond just passthrough.
> Any other games become dangerous and new code will have to be carefully reviewed every
> time, calling another device's free_sa when it wasn't added before doesn't sound good.
>
> >> GC may be running in parallel which probably means that in bond_ipsec_free_sa()
> >> you'll have to take the mutex before calling xdo_dev_state_free() and check
> >> if the entry is still linked in the bond's ipsec list before calling the free_sa
> >> callback, if it isn't then del_sa_all got to it before the GC and there's nothing
> >> to do if it also called the dev's free_sa callback. The check for real_dev doesn't
> >> seem enough to protect against this race.
> >
> > I agree that we need to take the mutex before calling xdo_dev_state_free()
> > in bond_ipsec_free_sa(). Do you think if this is enough? I'm a bit lot here.
> >
> > Thanks
> > Hangbin
>
> Well, the race is between the xfrm GC and del_sa_all, in bond's free_sa if you
> walk the list under the mutex before calling real_dev's free callback and
> don't find the current element that's being freed in free_sa then it was
> cleaned up by del_sa_all, otherwise del_sa_all is waiting to walk that
> list and clean the entries. I think it should be fine as long as free_sa
> was called once with the proper device.

OK, so the free will be called either in del_sa_all() or free_sa().
Something like this?

static void bond_ipsec_del_sa_all(struct bonding *bond)
@@ -620,6 +614,16 @@ static void bond_ipsec_del_sa_all(struct bonding *bond)
if (!ipsec->xs->xso.real_dev)
continue;

+ if (ipsec->xs->km.state == XFRM_STATE_DEAD) {
+ /* already dead no need to delete again */
+ if (real_dev->xfrmdev_ops->xdo_dev_state_free)
+ real_dev->xfrmdev_ops->xdo_dev_state_free(ipsec->xs);
+ list_del(&ipsec->list);
+ kfree(ipsec);
+ continue;
+ }
+
if (!real_dev->xfrmdev_ops ||
!real_dev->xfrmdev_ops->xdo_dev_state_delete ||
netif_is_bond_master(real_dev)) {

@@ -659,11 +664,22 @@ static void bond_ipsec_free_sa(struct xfrm_state *xs)
if (!xs->xso.real_dev)
goto out;

- WARN_ON(xs->xso.real_dev != real_dev);
+ mutex_lock(&bond->ipsec_lock);
+ list_for_each_entry(ipsec, &bond->ipsec_list, list) {
+ if (ipsec->xs == xs) {
+ if (real_dev && xs->xso.real_dev == real_dev &&

^^ looks we don't need this xs->xso.real_dev == real_dev
checking if there is no race, do we? Or just keep
the WARN_ON() in case of any race.

+ real_dev->xfrmdev_ops &&
+ real_dev->xfrmdev_ops->xdo_dev_state_free)
+ real_dev->xfrmdev_ops->xdo_dev_state_free(xs);
+ list_del(&ipsec->list);
+ kfree(ipsec);
+ break;
+ }
+ }
+ mutex_unlock(&bond->ipsec_lock);

- if (real_dev && real_dev->xfrmdev_ops &&
- real_dev->xfrmdev_ops->xdo_dev_state_free)
- real_dev->xfrmdev_ops->xdo_dev_state_free(xs);
out:
netdev_put(real_dev, &tracker);
}
--
2.39.5 (Apple Git-154)

Thanks
Hangbin