xfrm: policy: only use rcu in xfrm_sk_policy_lookup (ae33786f) · Commits · 戴 / test

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 <fw@strlen.de> Signed-off-by:

Steffen Klassert <steffen.klassert@secunet.com>

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;
		}

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