netfilter: ctnetlink: fix regression in expectation handling

This patch fixes a regression (introduced by myself in commit 19abb7b0:
netfilter: ctnetlink: deliver events for conntracks changed from
userspace) that results in an expectation re-insertion since
__nf_ct_expect_check() may return 0 for expectation timer refreshing.

This patch also removes a unnecessary refcount bump that
pretended to avoid a possible race condition with event delivery
and expectation timers (as said, not needed since we hold a
reference to the object since until we finish the expectation
setup). This also merges nf_ct_expect_related_report() and
nf_ct_expect_related() which look basically the same.
Reported-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

include/net/netfilter/nf_conntrack_expect.h

@@ -99,9 +99,12 @@ void nf_ct_expect_init(struct nf_conntrack_expect *, unsigned int, u_int8_t,
 		       const union nf_inet_addr *,
 		       u_int8_t, const __be16 *, const __be16 *);
 void nf_ct_expect_put(struct nf_conntrack_expect *exp);
-int nf_ct_expect_related(struct nf_conntrack_expect *expect);
 int nf_ct_expect_related_report(struct nf_conntrack_expect *expect, 
 				u32 pid, int report);
+static inline int nf_ct_expect_related(struct nf_conntrack_expect *expect)
+{
+	return nf_ct_expect_related_report(expect, 0, 0);
+}
 
 #endif /*_NF_CONNTRACK_EXPECT_H*/
 

net/netfilter/nf_conntrack_expect.c

@@ -372,7 +372,7 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect)
 	struct net *net = nf_ct_exp_net(expect);
 	struct hlist_node *n;
 	unsigned int h;
-	int ret = 0;
+	int ret = 1;
 
 	if (!master_help->helper) {
 		ret = -ESHUTDOWN;
@@ -412,43 +412,25 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect)
 	return ret;
 }
 
-int nf_ct_expect_related(struct nf_conntrack_expect *expect)
+int nf_ct_expect_related_report(struct nf_conntrack_expect *expect, 
+				u32 pid, int report)
 {
 	int ret;
 
 	spin_lock_bh(&nf_conntrack_lock);
 	ret = __nf_ct_expect_check(expect);
-	if (ret < 0)
+	if (ret <= 0)
 		goto out;
 
+	ret = 0;
 	nf_ct_expect_insert(expect);
-	atomic_inc(&expect->use);
 	spin_unlock_bh(&nf_conntrack_lock);
-	nf_ct_expect_event(IPEXP_NEW, expect);
-	nf_ct_expect_put(expect);
+	nf_ct_expect_event_report(IPEXP_NEW, expect, pid, report);
 	return ret;
 out:
 	spin_unlock_bh(&nf_conntrack_lock);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(nf_ct_expect_related);
-
-int nf_ct_expect_related_report(struct nf_conntrack_expect *expect, 
-				u32 pid, int report)
-{
-	int ret;
-
-	spin_lock_bh(&nf_conntrack_lock);
-	ret = __nf_ct_expect_check(expect);
-	if (ret < 0)
-		goto out;
-	nf_ct_expect_insert(expect);
-out:
-	spin_unlock_bh(&nf_conntrack_lock);
-	if (ret == 0)
-		nf_ct_expect_event_report(IPEXP_NEW, expect, pid, report);
-	return ret;
-}
 EXPORT_SYMBOL_GPL(nf_ct_expect_related_report);
 
 #ifdef CONFIG_PROC_FS