act_mirred: use the backlog for nested calls to mirred ingress

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2150278
CVE: CVE-2022-4269
Upstream Status: net-next.git commit ca22da2

commit ca22da2
Author: Davide Caratti <dcaratti@redhat.com>
Date:   Fri Jan 20 18:01:40 2023 +0100

    act_mirred: use the backlog for nested calls to mirred ingress

    William reports kernel soft-lockups on some OVS topologies when TC mirred
    egress->ingress action is hit by local TCP traffic [1].
    The same can also be reproduced with SCTP (thanks Xin for verifying), when
    client and server reach themselves through mirred egress to ingress, and
    one of the two peers sends a "heartbeat" packet (from within a timer).

    Enqueueing to backlog proved to fix this soft lockup; however, as Cong
    noticed [2], we should preserve - when possible - the current mirred
    behavior that counts as "overlimits" any eventual packet drop subsequent to
    the mirred forwarding action [3]. A compromise solution might use the
    backlog only when tcf_mirred_act() has a nest level greater than one:
    change tcf_mirred_forward() accordingly.

    Also, add a kselftest that can reproduce the lockup and verifies TC mirred
    ability to account for further packet drops after TC mirred egress->ingress
    (when the nest level is 1).

     [1] https://lore.kernel.org/netdev/33dc43f587ec1388ba456b4915c75f02a8aae226.1663945716.git.dcaratti@redhat.com/
     [2] https://lore.kernel.org/netdev/Y0w%2FWWY60gqrtGLp@pop-os.localdomain/
     [3] such behavior is not guaranteed: for example, if RPS or skb RX
         timestamping is enabled on the mirred target device, the kernel
         can defer receiving the skb and return NET_RX_SUCCESS inside
         tcf_mirred_forward().

    Reported-by: William Zhao <wizhao@redhat.com>
    CC: Xin Long <lucien.xin@gmail.com>
    Signed-off-by: Davide Caratti <dcaratti@redhat.com>
    Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Author: dcaratti

net/sched/act_mirred.c

@@ -206,12 +206,19 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
 	return err;
 }
 
+static bool is_mirred_nested(void)
+{
+	return unlikely(__this_cpu_read(mirred_nest_level) > 1);
+}
+
 static int tcf_mirred_forward(bool want_ingress, struct sk_buff *skb)
 {
 	int err;
 
 	if (!want_ingress)
 		err = tcf_dev_queue_xmit(skb, dev_queue_xmit);
+	else if (is_mirred_nested())
+		err = netif_rx(skb);
 	else
 		err = netif_receive_skb(skb);
 

tools/testing/selftests/net/forwarding/tc_actions.sh

@@ -3,7 +3,8 @@
 
 ALL_TESTS="gact_drop_and_ok_test mirred_egress_redirect_test \
 	mirred_egress_mirror_test matchall_mirred_egress_mirror_test \
-	gact_trap_test mirred_egress_to_ingress_test"
+	gact_trap_test mirred_egress_to_ingress_test \
+	mirred_egress_to_ingress_tcp_test"
 NUM_NETIFS=4
 source tc_common.sh
 source lib.sh
@@ -198,6 +199,52 @@ mirred_egress_to_ingress_test()
 	log_test "mirred_egress_to_ingress ($tcflags)"
 }
 
+mirred_egress_to_ingress_tcp_test()
+{
+	local tmpfile=$(mktemp) tmpfile1=$(mktemp)
+
+	RET=0
+	dd conv=sparse status=none if=/dev/zero bs=1M count=2 of=$tmpfile
+	tc filter add dev $h1 protocol ip pref 100 handle 100 egress flower \
+		$tcflags ip_proto tcp src_ip 192.0.2.1 dst_ip 192.0.2.2 \
+			action ct commit nat src addr 192.0.2.2 pipe \
+			action ct clear pipe \
+			action ct commit nat dst addr 192.0.2.1 pipe \
+			action ct clear pipe \
+			action skbedit ptype host pipe \
+			action mirred ingress redirect dev $h1
+	tc filter add dev $h1 protocol ip pref 101 handle 101 egress flower \
+		$tcflags ip_proto icmp \
+			action mirred ingress redirect dev $h1
+	tc filter add dev $h1 protocol ip pref 102 handle 102 ingress flower \
+		ip_proto icmp \
+			action drop
+
+	ip vrf exec v$h1 nc --recv-only -w10 -l -p 12345 -o $tmpfile1  &
+	local rpid=$!
+	ip vrf exec v$h1 nc -w1 --send-only 192.0.2.2 12345 <$tmpfile
+	wait -n $rpid
+	cmp -s $tmpfile $tmpfile1
+	check_err $? "server output check failed"
+
+	$MZ $h1 -c 10 -p 64 -a $h1mac -b $h1mac -A 192.0.2.1 -B 192.0.2.1 \
+		-t icmp "ping,id=42,seq=5" -q
+	tc_check_packets "dev $h1 egress" 101 10
+	check_err $? "didn't mirred redirect ICMP"
+	tc_check_packets "dev $h1 ingress" 102 10
+	check_err $? "didn't drop mirred ICMP"
+	local overlimits=$(tc_rule_stats_get ${h1} 101 egress .overlimits)
+	test ${overlimits} = 10
+	check_err $? "wrong overlimits, expected 10 got ${overlimits}"
+
+	tc filter del dev $h1 egress protocol ip pref 100 handle 100 flower
+	tc filter del dev $h1 egress protocol ip pref 101 handle 101 flower
+	tc filter del dev $h1 ingress protocol ip pref 102 handle 102 flower
+
+	rm -f $tmpfile $tmpfile1
+	log_test "mirred_egress_to_ingress_tcp ($tcflags)"
+}
+
 setup_prepare()
 {
 	h1=${NETIFS[p1]}