On Wed, Aug 9, 2017 at 8:57 AM, <gfree.w...@vip.163.com> wrote: > From: Gao Feng <gfree.w...@vip.163.com> > > In the commit ddab82821fa6 ("ppp: Fix a scheduling-while-atomic bug in > del_chan"), I moved the synchronize_rcu() from del_chan() to pptp_release > after del_chan() to avoid one scheduling-while-atomic bug. > > Actually the del_chan() and pppox_unbind_sock are unneccessary in the > pptp_sock_destruct. Because the pptp sock refcnt wouldn't reach zero until > sk_state is set as PPPOX_DEAD in pptp_release. By that time, the del_chan() > and pppox_unbind_sock() have been invoked already and the condition check > "!(sk->sk_state & PPPOX_DEAD)" of this sock must be false in > pptp_sock_destruct.
I am not sure. The check for sock->sk in the beginning of pptp_release() indicates there could be a case we could skip del_chan() in pptp_release(), although I can't figure out how. Also there is a suspicious sock_put() in pptp_release().