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From: Steffen Klassert <steffen.klassert@secunet.com>
To: David Miller <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	Steffen Klassert <steffen.klassert@secunet.com>,
	<netdev@vger.kernel.org>
Subject: [PATCH 2/6] Revert "xfrm: policy: Read seqcount outside of rcu-read side in xfrm_policy_lookup_bytype"
Date: Wed, 4 Aug 2021 09:03:25 +0200	[thread overview]
Message-ID: <20210804070329.1357123-3-steffen.klassert@secunet.com> (raw)
In-Reply-To: <20210804070329.1357123-1-steffen.klassert@secunet.com>

This reverts commit d7b0408934c749f546b01f2b33d07421a49b6f3e.

This commit tried to fix a locking bug introduced by commit 77cc278f7b20
("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: Steffen Klassert <steffen.klassert@secunet.com>
---
 net/xfrm/xfrm_policy.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index e9d0df2a2ab1..ce500f847b99 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2092,15 +2092,12 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
 	if (unlikely(!daddr || !saddr))
 		return NULL;
 
- retry:
-	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;
-	}
+ retry:
+	do {
+		sequence = read_seqcount_begin(&xfrm_policy_hash_generation);
+		chain = policy_hash_direct(net, daddr, saddr, family, dir);
+	} 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();
 
-- 
2.25.1


  parent reply	other threads:[~2021-08-04  7:03 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-04  7:03 pull request (net): ipsec 2021-08-04 Steffen Klassert
2021-08-04  7:03 ` [PATCH 1/6] net: xfrm: fix memory leak in xfrm_user_rcv_msg Steffen Klassert
2021-08-04 10:10   ` patchwork-bot+netdevbpf
2021-08-04  7:03 ` Steffen Klassert [this message]
2021-08-04  7:03 ` [PATCH 3/6] xfrm: Fix RCU vs hash_resize_mutex lock inversion Steffen Klassert
2021-08-04  7:03 ` [PATCH 4/6] net/xfrm/compat: Copy xfrm_spdattr_type_t atributes Steffen Klassert
2021-08-04  7:03 ` [PATCH 5/6] selftests/net/ipsec: Add test for xfrm_spdattr_type_t Steffen Klassert
2021-08-04  7:03 ` [PATCH 6/6] net: xfrm: Fix end of loop tests for list_for_each_entry Steffen Klassert
2021-08-04 10:10 ` pull request (net): ipsec 2021-08-04 patchwork-bot+netdevbpf

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