netfilter: ctnetlink: fix reliable event delivery if message building fails

This patch fixes a bug that allows to lose events when reliable
event delivery mode is used, ie. if NETLINK_BROADCAST_SEND_ERROR
and NETLINK_RECV_NO_ENOBUFS socket options are set.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 6 insertions, 4 deletions

diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index 53923868c9bd..361d6b5630ee 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -76,7 +76,7 @@ extern int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n);
 extern int nfnetlink_has_listeners(struct net *net, unsigned int group);
 extern int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid, unsigned group,
                           int echo, gfp_t flags);
-extern void nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error);
+extern int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error);
 extern int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u_int32_t pid, int flags);
 
 extern void nfnl_lock(void);
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 2b2af631d2b8..569410a85953 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -582,7 +582,9 @@ nla_put_failure:
 nlmsg_failure:
         kfree_skb(skb);
 errout:
-        nfnetlink_set_err(net, 0, group, -ENOBUFS);
+        if (nfnetlink_set_err(net, 0, group, -ENOBUFS) > 0)
+                return -ENOBUFS;
+
         return 0;
 }
 #endif /* CONFIG_NF_CONNTRACK_EVENTS */
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 8eb0cc23ada3..6afa3d52ea5f 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -113,9 +113,9 @@ int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 pid,
 }
 EXPORT_SYMBOL_GPL(nfnetlink_send);
 
-void nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
+int nfnetlink_set_err(struct net *net, u32 pid, u32 group, int error)
 {
-        netlink_set_err(net->nfnl, pid, group, error);
+        return netlink_set_err(net->nfnl, pid, group, error);
 }
 EXPORT_SYMBOL_GPL(nfnetlink_set_err);