netdev - [PATCH 13/17] xfrm: policy: only use rcu in xfrm_sk_policy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 8 Sep 2016 07:54:48 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     David Miller <davem@...emloft.net>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH 13/17] xfrm: policy: only use rcu in xfrm_sk_policy_lookup

From: Florian Westphal <fw@...len.de>

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@...len.de>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
---
 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 9302647..3d27b9a 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;
 }
-- 
1.9.1