Merge git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf

Florian Westphal says:

====================
netfilter: bug fixes for net

1. Fix IP address check in irc DCC conntrack helper, this should check
the opposite direction rather than the destination address of the
packets' direction, from David Leadbeater.

2. bridge netfilter needs to drop dst references, from Harsh Modi.
This was fine back in the day the code was originally written,
but nowadays various tunnels can pre-set metadata dsts on packets.

3. Remove nf_conntrack_helper sysctl and the modparam toggle, users
need to explicitily assign the helpers to use via nftables or
iptables. Conntrack helpers, by design, may be used to add dynamic
port redirections to internal machines, so its necessary to restrict
which hosts/peers are allowed to use them.
It was discovered that improper checking in the irc DCC helper makes
it possible to trigger the 'please do dynamic port forward'
from outside by embedding a 'DCC' in a PING request; if the client
echos that back a expectation/port forward gets added.
The auto-assign-for-everything mechanism has been in "please don't do this"
territory since 2012. From Pablo.

4. Fix a memory leak in the netdev hook error unwind path, also from Pablo.

* git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf:
netfilter: nf_conntrack_irc: Fix forged IP logic
netfilter: nf_tables: clean up hook list when offload flags check fails
netfilter: br_netfilter: Drop dst references before setting.
netfilter: remove nf_conntrack_helper sysctl and modparam toggles
====================

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/netfilter/nf_conntrack.h

···
 	/* only used when new connection is allocated: */
 	atomic_t count;
 	unsigned int expect_count;
-	u8 sysctl_auto_assign_helper;
-	bool auto_assign_helper_warned;
 
 	/* only used from work queues, configuration plane, and so on: */
 	unsigned int users4;

include/net/netns/conntrack.h

···
 	u8			sysctl_log_invalid; /* Log invalid packets */
 	u8			sysctl_events;
 	u8			sysctl_acct;
-	u8			sysctl_auto_assign_helper;
 	u8			sysctl_tstamp;
 	u8			sysctl_checksum;
 

net/bridge/br_netfilter_hooks.c

···
 				/* - Bridged-and-DNAT'ed traffic doesn't
 				 *   require ip_forwarding. */
 				if (rt->dst.dev == dev) {
+					skb_dst_drop(skb);
 					skb_dst_set(skb, &rt->dst);
 					goto bridged_dnat;
 				}
···
 			kfree_skb(skb);
 			return 0;
 		}
+		skb_dst_drop(skb);
 		skb_dst_set_noref(skb, &rt->dst);
 	}
 

net/bridge/br_netfilter_ipv6.c

···
 			kfree_skb(skb);
 			return 0;
 		}
+		skb_dst_drop(skb);
 		skb_dst_set_noref(skb, &rt->dst);
 	}
 

net/netfilter/nf_conntrack_core.c

···
 		}
 		spin_unlock_bh(&nf_conntrack_expect_lock);
 	}
-	if (!exp)
+	if (!exp && tmpl)
 		__nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);
 
 	/* Other CPU might have obtained a pointer to this object before it was
···
 	ct->tuplehash[IP_CT_DIR_REPLY].tuple = *newreply;
 	if (ct->master || (help && !hlist_empty(&help->expectations)))
 		return;
-
-	rcu_read_lock();
-	__nf_ct_try_assign_helper(ct, NULL, GFP_ATOMIC);
-	rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_alter_reply);
 
···
 	nf_conntrack_acct_pernet_init(net);
 	nf_conntrack_tstamp_pernet_init(net);
 	nf_conntrack_ecache_pernet_init(net);
-	nf_conntrack_helper_pernet_init(net);
 	nf_conntrack_proto_pernet_init(net);
 
 	return 0;

net/netfilter/nf_conntrack_helper.c

···
 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
 static unsigned int nf_ct_helper_count __read_mostly;
 
-static bool nf_ct_auto_assign_helper __read_mostly = false;
-module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
-MODULE_PARM_DESC(nf_conntrack_helper,
-		 "Enable automatic conntrack helper assignment (default 0)");
-
 static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
 static struct list_head nf_ct_nat_helpers __read_mostly;
 
···
 {
 	return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
 		(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
-}
-
-static struct nf_conntrack_helper *
-__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
-{
-	struct nf_conntrack_helper *helper;
-	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
-	unsigned int h;
-
-	if (!nf_ct_helper_count)
-		return NULL;
-
-	h = helper_hash(tuple);
-	hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
-		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
-			return helper;
-	}
-	return NULL;
 }
 
 struct nf_conntrack_helper *
···
 }
 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 
-static struct nf_conntrack_helper *
-nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
-{
-	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
-
-	if (!cnet->sysctl_auto_assign_helper) {
-		if (cnet->auto_assign_helper_warned)
-			return NULL;
-		if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
-			return NULL;
-		pr_info("nf_conntrack: default automatic helper assignment "
-			"has been turned off for security reasons and CT-based "
-			"firewall rule not found. Use the iptables CT target "
-			"to attach helpers instead.\n");
-		cnet->auto_assign_helper_warned = true;
-		return NULL;
-	}
-
-	return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
-}
-
 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 			      gfp_t flags)
 {
 	struct nf_conntrack_helper *helper = NULL;
 	struct nf_conn_help *help;
-	struct net *net = nf_ct_net(ct);
 
 	/* We already got a helper explicitly attached. The function
 	 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
···
 	if (test_bit(IPS_HELPER_BIT, &ct->status))
 		return 0;
 
-	if (tmpl != NULL) {
-		help = nfct_help(tmpl);
-		if (help != NULL) {
-			helper = rcu_dereference(help->helper);
-			set_bit(IPS_HELPER_BIT, &ct->status);
-		}
+	if (WARN_ON_ONCE(!tmpl))
+		return 0;
+
+	help = nfct_help(tmpl);
+	if (help != NULL) {
+		helper = rcu_dereference(help->helper);
+		set_bit(IPS_HELPER_BIT, &ct->status);
 	}
 
 	help = nfct_help(ct);
 
 	if (helper == NULL) {
-		helper = nf_ct_lookup_helper(ct, net);
-		if (helper == NULL) {
-			if (help)
-				RCU_INIT_POINTER(help->helper, NULL);
-			return 0;
-		}
+		if (help)
+			RCU_INIT_POINTER(help->helper, NULL);
+		return 0;
 	}
 
 	if (help == NULL) {
···
 	mutex_unlock(&nf_ct_nat_helpers_mutex);
 }
 EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
-
-void nf_ct_set_auto_assign_helper_warned(struct net *net)
-{
-	nf_ct_pernet(net)->auto_assign_helper_warned = true;
-}
-EXPORT_SYMBOL_GPL(nf_ct_set_auto_assign_helper_warned);
-
-void nf_conntrack_helper_pernet_init(struct net *net)
-{
-	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
-
-	cnet->sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
-}
 
 int nf_conntrack_helper_init(void)
 {

net/netfilter/nf_conntrack_irc.c

···
 
 			/* dcc_ip can be the internal OR external (NAT'ed) IP */
 			tuple = &ct->tuplehash[dir].tuple;
-			if (tuple->src.u3.ip != dcc_ip &&
-			    tuple->dst.u3.ip != dcc_ip) {
+			if ((tuple->src.u3.ip != dcc_ip &&
+			     ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) ||
+			    dcc_port == 0) {
 				net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n",
 						     &tuple->src.u3.ip,
 						     &dcc_ip, dcc_port);

net/netfilter/nf_conntrack_netlink.c

···
 			ct->status |= IPS_HELPER;
 			RCU_INIT_POINTER(help->helper, helper);
 		}
-	} else {
-		/* try an implicit helper assignation */
-		err = __nf_ct_try_assign_helper(ct, NULL, GFP_ATOMIC);
-		if (err < 0)
-			goto err2;
 	}
 
 	err = ctnetlink_setup_nat(ct, cda);

net/netfilter/nf_conntrack_standalone.c

···
 	NF_SYSCTL_CT_LOG_INVALID,
 	NF_SYSCTL_CT_EXPECT_MAX,
 	NF_SYSCTL_CT_ACCT,
-	NF_SYSCTL_CT_HELPER,
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	NF_SYSCTL_CT_EVENTS,
 #endif
···
 	[NF_SYSCTL_CT_ACCT] = {
 		.procname	= "nf_conntrack_acct",
 		.data		= &init_net.ct.sysctl_acct,
-		.maxlen		= sizeof(u8),
-		.mode		= 0644,
-		.proc_handler	= proc_dou8vec_minmax,
-		.extra1 	= SYSCTL_ZERO,
-		.extra2 	= SYSCTL_ONE,
-	},
-	[NF_SYSCTL_CT_HELPER] = {
-		.procname	= "nf_conntrack_helper",
 		.maxlen		= sizeof(u8),
 		.mode		= 0644,
 		.proc_handler	= proc_dou8vec_minmax,
···
 	table[NF_SYSCTL_CT_CHECKSUM].data = &net->ct.sysctl_checksum;
 	table[NF_SYSCTL_CT_LOG_INVALID].data = &net->ct.sysctl_log_invalid;
 	table[NF_SYSCTL_CT_ACCT].data = &net->ct.sysctl_acct;
-	table[NF_SYSCTL_CT_HELPER].data = &cnet->sysctl_auto_assign_helper;
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	table[NF_SYSCTL_CT_EVENTS].data = &net->ct.sysctl_events;
 #endif

net/netfilter/nf_tables_api.c

···
 	chain->flags |= NFT_CHAIN_BASE | flags;
 	basechain->policy = NF_ACCEPT;
 	if (chain->flags & NFT_CHAIN_HW_OFFLOAD &&
-	    !nft_chain_offload_support(basechain))
+	    !nft_chain_offload_support(basechain)) {
+		list_splice_init(&basechain->hook_list, &hook->list);
 		return -EOPNOTSUPP;
+	}
 
 	flow_block_init(&basechain->flow_block);
 

net/netfilter/nft_ct.c

···
 	if (err < 0)
 		goto err_put_helper;
 
-	/* Avoid the bogus warning, helper will be assigned after CT init */
-	nf_ct_set_auto_assign_helper_warned(ctx->net);
-
 	return 0;
 
 err_put_helper:

tools/testing/selftests/netfilter/nft_conntrack_helper.sh

···
 
 	ip netns exec ${netns} conntrack -L -f $family -p tcp --dport $port 2> /dev/null |grep -q 'helper=ftp'
 	if [ $? -ne 0 ] ; then
-		echo "FAIL: ${netns} did not show attached helper $message" 1>&2
-		ret=1
+		if [ $autoassign -eq 0 ] ;then
+			echo "FAIL: ${netns} did not show attached helper $message" 1>&2
+			ret=1
+		else
+			echo "PASS: ${netns} did not show attached helper $message" 1>&2
+		fi
+	else
+		if [ $autoassign -eq 0 ] ;then
+			echo "PASS: ${netns} connection on port $port has ftp helper attached" 1>&2
+		else
+			echo "FAIL: ${netns} connection on port $port has ftp helper attached" 1>&2
+			ret=1
+		fi
 	fi
 
-	echo "PASS: ${netns} connection on port $port has ftp helper attached" 1>&2
 	return 0
 }
 
 test_helper()
 {
 	local port=$1
-	local msg=$2
+	local autoassign=$2
+
+	if [ $autoassign -eq 0 ] ;then
+		msg="set via ruleset"
+	else
+		msg="auto-assign"
+	fi
 
 	sleep 3 | ip netns exec ${ns2} nc -w 2 -l -p $port > /dev/null &
 
 	sleep 1 | ip netns exec ${ns1} nc -w 2 10.0.1.2 $port > /dev/null &
 	sleep 1
 
-	check_for_helper "$ns1" "ip $msg" $port
-	check_for_helper "$ns2" "ip $msg" $port
+	check_for_helper "$ns1" "ip $msg" $port $autoassign
+	check_for_helper "$ns2" "ip $msg" $port $autoassign
 
 	wait
 
···
 	fi
 fi
 
-test_helper 2121 "set via ruleset"
-ip netns exec ${ns1} sysctl -q 'net.netfilter.nf_conntrack_helper=1'
-ip netns exec ${ns2} sysctl -q 'net.netfilter.nf_conntrack_helper=1'
-test_helper 21 "auto-assign"
+test_helper 2121 0
+ip netns exec ${ns1} sysctl -qe 'net.netfilter.nf_conntrack_helper=1'
+ip netns exec ${ns2} sysctl -qe 'net.netfilter.nf_conntrack_helper=1'
+test_helper 21 1
 
 exit $ret