Re: [PATCH net-next 1/1] driver: pptp: Remove unnecessary statements in pptp_sock_destruct

On Wed, Aug 9, 2017 at 8:57 AM,  [off-list ref] wrote:

From: Gao Feng <redacted>

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().