Messages in this thread | | | Subject | Re: [PATCH net-next] tuntap: fix possible deadlock when fail to register netdev | From | Jason Wang <> | Date | Fri, 8 Dec 2017 11:27:22 +0800 |
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On 2017年12月08日 11:11, Eric Dumazet wrote: > 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.dumazet@gmail.com> >> Cc: Eric Dumazet <eric.dumazet@gmail.com> >> Cc: Willem de Bruijn <willemb@google.com> >> Signed-off-by: Jason Wang <jasowang@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 ?
No I test without it.
> > My gut feeling is that you need spin_lock_bh() here. > > Thanks >
Yes, I miss the fact this the lock is used by e.g flow caches too. Will post V2.
Thanks
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