Re: [bug report] net/mlx5e: Handle FIB events to update tunnel endpoint device

[Ido Schimmel <idosch@idosch.org>]

On Wed, Feb 10, 2021 at 03:50:03PM +0200, Vlad Buslov wrote:
> 
> On Wed 10 Feb 2021 at 15:21, Ido Schimmel <idosch@idosch.org> wrote:
> > On Wed, Feb 10, 2021 at 01:55:23PM +0200, Vlad Buslov wrote:
> >> On Wed 10 Feb 2021 at 13:08, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >> > Hello Vlad Buslov,
> >> >
> >> > The patch 8914add2c9e5: "net/mlx5e: Handle FIB events to update
> >> > tunnel endpoint device" from Jan 25, 2021, leads to the following
> >> > static checker warning:
> >> >
> >> > 	drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_encap.c:1639 mlx5e_tc_tun_init()
> >> > 	error: passing non negative 1 to ERR_PTR
> >> >
> >> > drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_encap.c
> >> >   1622  struct mlx5e_tc_tun_encap *mlx5e_tc_tun_init(struct mlx5e_priv *priv)
> >> >   1623  {
> >> >   1624          struct mlx5e_tc_tun_encap *encap;
> >> >   1625          int err;
> >> >   1626  
> >> >   1627          encap = kvzalloc(sizeof(*encap), GFP_KERNEL);
> >> >   1628          if (!encap)
> >> >   1629                  return ERR_PTR(-ENOMEM);
> >> >   1630  
> >> >   1631          encap->priv = priv;
> >> >   1632          encap->fib_nb.notifier_call = mlx5e_tc_tun_fib_event;
> >> >   1633          spin_lock_init(&encap->route_lock);
> >> >   1634          hash_init(encap->route_tbl);
> >> >   1635          err = register_fib_notifier(dev_net(priv->netdev), &encap->fib_nb,
> >> >   1636                                      NULL, NULL);
> >> >
> >> > register_fib_notifier() calls fib_net_dump() which eventually calls
> >> > fib6_walk_continue() which can return 1 if "walk is incomplete (i.e.
> >> > suspended)".
> >> >
> >> >   1637          if (err) {
> >> >   1638                  kvfree(encap);
> >> >   1639                  return ERR_PTR(err);
> >> >
> >> > If this returns 1 it will eventually lead to an Oops.
> >> 
> >> Hi Dan,
> >> 
> >> Thanks for the bug report!
> >> 
> >> This looks a bit strange to me because none of the other users of this
> >> API handle positive error code in any special way (including reference
> >> netdevsim implementation). Maybe API itself should be fixed? Jiri, Ido,
> >> what do you think?
> >
> > The other functions that call register_fib_notifier() return an int, but
> > mlx5e_tc_tun_init() returns a pointer. I think that's why it was
> > flagged: "error: passing non negative 1 to ERR_PTR".
> 
> Actually, some of them do. I mentioned netdevsim specifically because
> nsim_fib_create() returns pointer and also casts return value of
> register_fib_notifier() with ERR_PTR.
> 
> >
> > fib6_walk_continue() cannot return a positive value when called from
> > register_fib_notifier(), but ignoring it means that you will keep
> > getting the same static analysis error. What about:
> >
> > diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
> > index f43e27555725..ef9d022e693f 100644
> > --- a/net/ipv6/ip6_fib.c
> > +++ b/net/ipv6/ip6_fib.c
> > @@ -499,7 +499,7 @@ int fib6_tables_dump(struct net *net, struct notifier_block *nb,
> >  
> >                 hlist_for_each_entry_rcu(tb, head, tb6_hlist) {
> >                         err = fib6_table_dump(net, tb, w);
> > -                       if (err < 0)
> > +                       if (err)
> >                                 goto out;
> >                 }
> >         }
> > @@ -507,7 +507,8 @@ int fib6_tables_dump(struct net *net, struct notifier_block *nb,
> >  out:
> >         kfree(w);
> >  
> > -       return err;
> > +       /* The tree traversal function should never return a positive value. */
> > +       return err > 0 ? -EINVAL : err;
> >  }
> >  
> >  static int fib6_dump_node(struct fib6_walker *w)
> >
> 
> Makes sense. You want me to send the fix or you will do it?

Can you send to linux-internal and then I will apply it to our
regression and let you know tomorrow morning?

> 
> >> 
> >> Regards,
> >> Vlad
> >> 
> >> >
> >> >   1640          }
> >> >   1641  
> >> >   1642          return encap;
> >> >   1643  }
> >> >
> >> > regards,
> >> > dan carpenter
> >> 
>