netfilter: ctnetlink: fix regression in expectation handling

This patch fixes a regression (introduced by myself in commit 19abb7b:
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>

1 files changed, 6 insertions, 24 deletions

diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index 3940f996a2e4..afde8f991646 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/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;
@@ -412,41 +412,23 @@ out:
         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);
-        return ret;
-out:
         spin_unlock_bh(&nf_conntrack_lock);
+        nf_ct_expect_event_report(IPEXP_NEW, expect, pid, report);
         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);