On Fri, 2017-12-08 at 10:54 +0800, Jason Wang wrote: > Private destructor could be called when register_netdev() fail with > rtnl lock held. This will lead deadlock in tun_free_netdev() who > tries > to hold rtnl_lock. Fixing this by switching to use spinlock to > synchronize. > > Fixes: 96f84061620c ("tun: add eBPF based queue selection method") > Reported-by: Eric Dumazet <eric.duma...@gmail.com> > Cc: Eric Dumazet <eric.duma...@gmail.com> > Cc: Willem de Bruijn <will...@google.com> > Signed-off-by: Jason Wang <jasow...@redhat.com> > --- > drivers/net/tun.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index 787cc35..f7ccd79 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -2050,8 +2050,11 @@ static int __tun_set_steering_ebpf(struct > tun_struct *tun, > new->prog = prog; > } > > - old = rtnl_dereference(tun->steering_prog); > + spin_lock(&tun->lock); > + old = rcu_dereference_protected(tun->steering_prog, > + lock_is_held(&tun->lock)); > rcu_assign_pointer(tun->steering_prog, new); > + spin_unlock(&tun->lock); >
Hi Jason, thank you for the following up. Have you tested this code path with lockdep enabled ? My gut feeling is that you need spin_lock_bh() here. Thanks