From ae33786f73a7ce5b15ce29e8f342e43606385cef Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 11 Aug 2016 15:17:57 +0200 Subject: [PATCH] xfrm: policy: only use rcu in xfrm_sk_policy_lookup Don't acquire the readlock anymore and rely on rcu alone. In case writer on other CPU changed policy at the wrong moment (after we obtained sk policy pointer but before we could obtain the reference) just repeat the lookup. Signed-off-by: Florian Westphal Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_policy.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 9302647f20a0..3d27b9a2fbac 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1249,10 +1249,9 @@ static struct xfrm_policy *xfrm_sk_policy_lookup(const struct sock *sk, int dir, const struct flowi *fl) { struct xfrm_policy *pol; - struct net *net = sock_net(sk); rcu_read_lock(); - read_lock_bh(&net->xfrm.xfrm_policy_lock); + again: pol = rcu_dereference(sk->sk_policy[dir]); if (pol != NULL) { bool match = xfrm_selector_match(&pol->selector, fl, @@ -1267,8 +1266,8 @@ static struct xfrm_policy *xfrm_sk_policy_lookup(const struct sock *sk, int dir, err = security_xfrm_policy_lookup(pol->security, fl->flowi_secid, policy_to_flow_dir(dir)); - if (!err) - xfrm_pol_hold(pol); + if (!err && !xfrm_pol_hold_rcu(pol)) + goto again; else if (err == -ESRCH) pol = NULL; else @@ -1277,7 +1276,6 @@ static struct xfrm_policy *xfrm_sk_policy_lookup(const struct sock *sk, int dir, pol = NULL; } out: - read_unlock_bh(&net->xfrm.xfrm_policy_lock); rcu_read_unlock(); return pol; } -- 2.39.5