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

Hangbin Liu
2025-03-06T09:37:53Z

On Wed, Mar 05, 2025 at 04:12:18PM +0000, Cosmin Ratiu wrote:
> On Wed, 2025-03-05 at 14:13 +0000, Hangbin Liu wrote:
> > On Wed, Mar 05, 2025 at 10:38:36AM +0200, Nikolay Aleksandrov wrote:
> > > > @@ -617,8 +614,18 @@ static void bond_ipsec_del_sa_all(struct
> > > > bonding *bond)
> > > >
> > > >   mutex_lock(&bond->ipsec_lock);
> > > >   list_for_each_entry(ipsec, &bond->ipsec_list, list) {
> > >
> > > Second time - you should use list_for_each_entry_safe if you're
> > > walking and deleting
> > > elements from the list.
> >
> > Sorry, I missed this comment. I will update in next version.
> >
> > >
> > > > + spin_lock_bh(&ipsec->xs->lock);
> > > >   if (!ipsec->xs->xso.real_dev)
> > > > - continue;
> > > > + goto next;
> > > > +
> > > > + 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);
> > >
> > > Have you checked if .xdo_dev_state_free can sleep?
> > > I see at least one that can: mlx5e_xfrm_free_state().
> >
> > Hmm, This brings us back to the initial problem. We tried to avoid
> > calling
> > a spin lock in a sleep context (bond_ipsec_del_sa), but now the new
> > code
> > encounters this issue again.
>
> 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()

Thanks
Hangbin

> + /* Unlock before freeing device state, it could sleep.
> */
> + spin_unlock(&ipsec->x->lock);
> + if (real_dev->xfrmdev_ops->xdo_dev_state_free)
> + real_dev->xfrmdev_ops-
> >xdo_dev_state_free(ipsec->xs);
>
> Cosmin.