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Date: Sun, 19 Aug 2012 12:31:48 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>, fan.du@...driver.com,
fengguang.wu@...el.com, Priyanka Jain <Priyanka.Jain@...escale.com>
Subject: [PATCH net-next] xfrm: fix RCU bugs
From: Eric Dumazet <edumazet@...gle.com>
This patch reverts commit 56892261ed1a (xfrm: Use rcu_dereference_bh to
deference pointer protected by rcu_read_lock_bh), and fixes bugs
introduced in commit 418a99ac6ad ( Replace rwlock on xfrm_policy_afinfo
with rcu )
1) We properly use RCU variant in this file, not a mix of RCU/RCU_BH
2) We must defer some writes after the synchronize_rcu() call or a reader
can crash dereferencing NULL pointer.
3) Now we use the xfrm_policy_afinfo_lock spinlock only from process
context, we no longer need to block BH in xfrm_policy_register_afinfo()
and xfrm_policy_unregister_afinfo()
4) Can use RCU_INIT_POINTER() instead of rcu_assign_pointer() in
xfrm_policy_unregister_afinfo()
5) Remove a forward inline declaration (xfrm_policy_put_afinfo()),
and also move xfrm_policy_get_afinfo() declaration.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Fan Du <fan.du@...driver.com>
Cc: Priyanka Jain <Priyanka.Jain@...escale.com>
---
net/xfrm/xfrm_policy.c | 76 ++++++++++++++++++++-------------------
1 file changed, 39 insertions(+), 37 deletions(-)
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 6405764..e52f50f 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -48,8 +48,6 @@ static struct xfrm_policy_afinfo __rcu *xfrm_policy_afinfo[NPROTO]
static struct kmem_cache *xfrm_dst_cache __read_mostly;
-static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family);
-static inline void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo);
static void xfrm_init_pmtu(struct dst_entry *dst);
static int stale_bundle(struct dst_entry *dst);
static int xfrm_bundle_ok(struct xfrm_dst *xdst);
@@ -96,6 +94,24 @@ bool xfrm_selector_match(const struct xfrm_selector *sel, const struct flowi *fl
return false;
}
+static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family)
+{
+ struct xfrm_policy_afinfo *afinfo;
+
+ if (unlikely(family >= NPROTO))
+ return NULL;
+ rcu_read_lock();
+ afinfo = rcu_dereference(xfrm_policy_afinfo[family]);
+ if (unlikely(!afinfo))
+ rcu_read_unlock();
+ return afinfo;
+}
+
+static void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo)
+{
+ rcu_read_unlock();
+}
+
static inline struct dst_entry *__xfrm_dst_lookup(struct net *net, int tos,
const xfrm_address_t *saddr,
const xfrm_address_t *daddr,
@@ -2419,7 +2435,7 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
return -EINVAL;
if (unlikely(afinfo->family >= NPROTO))
return -EAFNOSUPPORT;
- spin_lock_bh(&xfrm_policy_afinfo_lock);
+ spin_lock(&xfrm_policy_afinfo_lock);
if (unlikely(xfrm_policy_afinfo[afinfo->family] != NULL))
err = -ENOBUFS;
else {
@@ -2442,7 +2458,7 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
afinfo->garbage_collect = xfrm_garbage_collect_deferred;
rcu_assign_pointer(xfrm_policy_afinfo[afinfo->family], afinfo);
}
- spin_unlock_bh(&xfrm_policy_afinfo_lock);
+ spin_unlock(&xfrm_policy_afinfo_lock);
rtnl_lock();
for_each_net(net) {
@@ -2475,23 +2491,26 @@ int xfrm_policy_unregister_afinfo(struct xfrm_policy_afinfo *afinfo)
return -EINVAL;
if (unlikely(afinfo->family >= NPROTO))
return -EAFNOSUPPORT;
- spin_lock_bh(&xfrm_policy_afinfo_lock);
+ spin_lock(&xfrm_policy_afinfo_lock);
if (likely(xfrm_policy_afinfo[afinfo->family] != NULL)) {
if (unlikely(xfrm_policy_afinfo[afinfo->family] != afinfo))
err = -EINVAL;
- else {
- struct dst_ops *dst_ops = afinfo->dst_ops;
- rcu_assign_pointer(xfrm_policy_afinfo[afinfo->family],
- NULL);
- dst_ops->kmem_cachep = NULL;
- dst_ops->check = NULL;
- dst_ops->negative_advice = NULL;
- dst_ops->link_failure = NULL;
- afinfo->garbage_collect = NULL;
- }
+ else
+ RCU_INIT_POINTER(xfrm_policy_afinfo[afinfo->family],
+ NULL);
+ }
+ spin_unlock(&xfrm_policy_afinfo_lock);
+ if (!err) {
+ struct dst_ops *dst_ops = afinfo->dst_ops;
+
+ synchronize_rcu();
+
+ dst_ops->kmem_cachep = NULL;
+ dst_ops->check = NULL;
+ dst_ops->negative_advice = NULL;
+ dst_ops->link_failure = NULL;
+ afinfo->garbage_collect = NULL;
}
- spin_unlock_bh(&xfrm_policy_afinfo_lock);
- synchronize_rcu();
return err;
}
EXPORT_SYMBOL(xfrm_policy_unregister_afinfo);
@@ -2500,32 +2519,15 @@ static void __net_init xfrm_dst_ops_init(struct net *net)
{
struct xfrm_policy_afinfo *afinfo;
- rcu_read_lock_bh();
- afinfo = rcu_dereference_bh(xfrm_policy_afinfo[AF_INET]);
+ rcu_read_lock();
+ afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET]);
if (afinfo)
net->xfrm.xfrm4_dst_ops = *afinfo->dst_ops;
#if IS_ENABLED(CONFIG_IPV6)
- afinfo = rcu_dereference_bh(xfrm_policy_afinfo[AF_INET6]);
+ afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET6]);
if (afinfo)
net->xfrm.xfrm6_dst_ops = *afinfo->dst_ops;
#endif
- rcu_read_unlock_bh();
-}
-
-static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family)
-{
- struct xfrm_policy_afinfo *afinfo;
- if (unlikely(family >= NPROTO))
- return NULL;
- rcu_read_lock();
- afinfo = rcu_dereference(xfrm_policy_afinfo[family]);
- if (unlikely(!afinfo))
- rcu_read_unlock();
- return afinfo;
-}
-
-static inline void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo)
-{
rcu_read_unlock();
}
--
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