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Commit ae33786f authored by Florian Westphal's avatar Florian Westphal Committed by Steffen Klassert
Browse files

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: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent a7c44247

net/xfrm/xfrm_policy.c

+3 −5
Original line number Diff line number Diff line
@@ -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;

}