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

[Hangbin Liu <liuhangbin@gmail.com>]

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.