On Thu, Mar 31, 2016 at 07:22:32AM +0200, Michal Kubecek wrote: > On Wed, Mar 30, 2016 at 10:08:10PM -0700, Alexei Starovoitov wrote: > > On Thu, Mar 31, 2016 at 07:01:15AM +0200, Michal Kubecek wrote: > > > On Wed, Mar 30, 2016 at 06:18:42PM -0700, Alexei Starovoitov wrote: > > > > > > > > kinda heavy patch to shut up lockdep. > > > > Can we do > > > > old_fp = rcu_dereference_protected(sk->sk_filter, > > > > sock_owned_by_user(sk) || > > > > lockdep_rtnl_is_held()); > > > > and it always be correct? > > > > I think right now tun is the only such user, but if it's correct > > > > for tun, it's correct for future users too. If not correct then > > > > not correct for tun either. > > > > Or I'm missing something? > > > > > > Already discussed here: > > > > > > http://thread.gmane.org/gmane.linux.kernel/2158069/focus=405853 > > > > I saw that. My point above was challenging 'less accurate' part. > > > Daniel's point was that lockdep_rtnl_is_held() does not mean "we hold > RTNL" but "someone holds RTNL" so that some other task holding RTNL at > the moment could make the check happy even when called by someone > supposed to own the socket.
Of course... and that is the case for all rtnl_dereference() calls... yet we're not paranoid about it.
