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.
So we could remove these statements in pptp_sock_destruct, and then restore
the synchronize_rcu() into del_chan.
Signed-off-by: Gao Feng <gfree.w...@vip.163.com>
---
drivers/net/ppp/pptp.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c
index 6dde9a0..8632e1a 100644
--- a/drivers/net/ppp/pptp.c
+++ b/drivers/net/ppp/pptp.c
@@ -131,6 +131,7 @@ static void del_chan(struct pppox_sock *sock)
clear_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap);
RCU_INIT_POINTER(callid_sock[sock->proto.pptp.src_addr.call_id], NULL);
spin_unlock(&chan_lock);
+ synchronize_rcu();
}
static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
@@ -519,7 +520,6 @@ static int pptp_release(struct socket *sock)
po = pppox_sk(sk);
del_chan(po);
- synchronize_rcu();
pppox_unbind_sock(sk);
sk->sk_state = PPPOX_DEAD;
@@ -535,10 +535,6 @@ static int pptp_release(struct socket *sock)
static void pptp_sock_destruct(struct sock *sk)
{
- if (!(sk->sk_state & PPPOX_DEAD)) {
- del_chan(pppox_sk(sk));
- pppox_unbind_sock(sk);
- }
skb_queue_purge(&sk->sk_receive_queue);
}
--
1.9.1
