Commit eaf22826 authored by Steffen Klassert's avatar Steffen Klassert
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Revert "xfrm: policy: Read seqcount outside of rcu-read side in xfrm_policy_lookup_bytype" 



This reverts commit d7b04089.

This commit tried to fix a locking bug introduced by commit 77cc278f
("xfrm: policy: Use sequence counters with associated lock"). As it
turned out, this patch did not really fix the bug. A proper fix
for this bug is applied on top of this revert.

Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent 7c1a80e8

net/xfrm/xfrm_policy.c

+7 −14
Original line number Diff line number Diff line
@@ -2092,15 +2092,12 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type, 
	if (unlikely(!daddr || !saddr))

		return NULL;



	rcu_read_lock();

 retry:

	do {

		sequence = read_seqcount_begin(&xfrm_policy_hash_generation);

	rcu_read_lock();



		chain = policy_hash_direct(net, daddr, saddr, family, dir);

	if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence)) {

		rcu_read_unlock();

		goto retry;

	}

	} while (read_seqcount_retry(&xfrm_policy_hash_generation, sequence));



	ret = NULL;

	hlist_for_each_entry_rcu(pol, chain, bydst) {
@@ -2131,15 +2128,11 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type, 
	}



skip_inexact:

	if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence)) {

		rcu_read_unlock();

	if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence))

		goto retry;

	}



	if (ret && !xfrm_pol_hold_rcu(ret)) {

		rcu_read_unlock();

	if (ret && !xfrm_pol_hold_rcu(ret))

		goto retry;

	}

fail:

	rcu_read_unlock();