Merge branch 'ipmr-always-call-ip-6-_mr_forward-from-rcu-read-side-critical-section'

Ido Schimmel says:

====================
ipmr: Always call ip{,6}_mr_forward() from RCU read-side critical section

Patch #1 fixes a bug in ipmr code.

Patch #2 adds corresponding test cases.
====================

Link: https://lore.kernel.org/r/20220914075339.4074096-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 97 insertions, 2 deletions

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 73651d17e51f31..e11d6b0b62b76e 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1004,7 +1004,9 @@ static void ipmr_cache_resolve(struct net *net, struct mr_table *mrt,
 
 			rtnl_unicast(skb, net, NETLINK_CB(skb).portid);
 		} else {
+			rcu_read_lock();
 			ip_mr_forward(net, mrt, skb->dev, skb, c, 0);
+			rcu_read_unlock();
 		}
 	}
 }
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index a9ba41648e3685..858fd8a28b5b2c 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1028,8 +1028,11 @@ static void ip6mr_cache_resolve(struct net *net, struct mr_table *mrt,
 				((struct nlmsgerr *)nlmsg_data(nlh))->error = -EMSGSIZE;
 			}
 			rtnl_unicast(skb, net, NETLINK_CB(skb).portid);
-		} else
+		} else {
+			rcu_read_lock();
 			ip6_mr_forward(net, mrt, skb->dev, skb, c);
+			rcu_read_unlock();
+		}
 	}
 }
 
diff --git a/tools/testing/selftests/net/forwarding/router_multicast.sh b/tools/testing/selftests/net/forwarding/router_multicast.sh
index 57e90c873a2cf4..5a58b1ec8aefb5 100755
--- a/tools/testing/selftests/net/forwarding/router_multicast.sh
+++ b/tools/testing/selftests/net/forwarding/router_multicast.sh
@@ -28,7 +28,7 @@
 # +------------------+       +------------------+
 #
 
-ALL_TESTS="mcast_v4 mcast_v6 rpf_v4 rpf_v6"
+ALL_TESTS="mcast_v4 mcast_v6 rpf_v4 rpf_v6 unres_v4 unres_v6"
 NUM_NETIFS=6
 source lib.sh
 source tc_common.sh
@@ -406,6 +406,96 @@ rpf_v6()
 	log_test "RPF IPv6"
 }
 
+unres_v4()
+{
+	# Send a multicast packet not corresponding to an installed route,
+	# causing the kernel to queue the packet for resolution and emit an
+	# IGMPMSG_NOCACHE notification. smcrouted will react to this
+	# notification by consulting its (*, G) list and installing an (S, G)
+	# route, which will be used to forward the queued packet.
+
+	RET=0
+
+	tc filter add dev $h2 ingress protocol ip pref 1 handle 1 flower \
+		dst_ip 225.1.2.3 ip_proto udp dst_port 12345 action drop
+	tc filter add dev $h3 ingress protocol ip pref 1 handle 1 flower \
+		dst_ip 225.1.2.3 ip_proto udp dst_port 12345 action drop
+
+	# Forwarding should fail before installing a matching (*, G).
+	$MZ $h1 -c 1 -p 128 -t udp "ttl=10,sp=54321,dp=12345" \
+		-a 00:11:22:33:44:55 -b 01:00:5e:01:02:03 \
+		-A 198.51.100.2 -B 225.1.2.3 -q
+
+	tc_check_packets "dev $h2 ingress" 1 0
+	check_err $? "Multicast received on first host when should not"
+	tc_check_packets "dev $h3 ingress" 1 0
+	check_err $? "Multicast received on second host when should not"
+
+	# Create (*, G). Will not be installed in the kernel.
+	create_mcast_sg $rp1 0.0.0.0 225.1.2.3 $rp2 $rp3
+
+	$MZ $h1 -c 1 -p 128 -t udp "ttl=10,sp=54321,dp=12345" \
+		-a 00:11:22:33:44:55 -b 01:00:5e:01:02:03 \
+		-A 198.51.100.2 -B 225.1.2.3 -q
+
+	tc_check_packets "dev $h2 ingress" 1 1
+	check_err $? "Multicast not received on first host"
+	tc_check_packets "dev $h3 ingress" 1 1
+	check_err $? "Multicast not received on second host"
+
+	delete_mcast_sg $rp1 0.0.0.0 225.1.2.3 $rp2 $rp3
+
+	tc filter del dev $h3 ingress protocol ip pref 1 handle 1 flower
+	tc filter del dev $h2 ingress protocol ip pref 1 handle 1 flower
+
+	log_test "Unresolved queue IPv4"
+}
+
+unres_v6()
+{
+	# Send a multicast packet not corresponding to an installed route,
+	# causing the kernel to queue the packet for resolution and emit an
+	# MRT6MSG_NOCACHE notification. smcrouted will react to this
+	# notification by consulting its (*, G) list and installing an (S, G)
+	# route, which will be used to forward the queued packet.
+
+	RET=0
+
+	tc filter add dev $h2 ingress protocol ipv6 pref 1 handle 1 flower \
+		dst_ip ff0e::3 ip_proto udp dst_port 12345 action drop
+	tc filter add dev $h3 ingress protocol ipv6 pref 1 handle 1 flower \
+		dst_ip ff0e::3 ip_proto udp dst_port 12345 action drop
+
+	# Forwarding should fail before installing a matching (*, G).
+	$MZ $h1 -6 -c 1 -p 128 -t udp "ttl=10,sp=54321,dp=12345" \
+		-a 00:11:22:33:44:55 -b 33:33:00:00:00:03 \
+		-A 2001:db8:1::2 -B ff0e::3 -q
+
+	tc_check_packets "dev $h2 ingress" 1 0
+	check_err $? "Multicast received on first host when should not"
+	tc_check_packets "dev $h3 ingress" 1 0
+	check_err $? "Multicast received on second host when should not"
+
+	# Create (*, G). Will not be installed in the kernel.
+	create_mcast_sg $rp1 :: ff0e::3 $rp2 $rp3
+
+	$MZ $h1 -6 -c 1 -p 128 -t udp "ttl=10,sp=54321,dp=12345" \
+		-a 00:11:22:33:44:55 -b 33:33:00:00:00:03 \
+		-A 2001:db8:1::2 -B ff0e::3 -q
+
+	tc_check_packets "dev $h2 ingress" 1 1
+	check_err $? "Multicast not received on first host"
+	tc_check_packets "dev $h3 ingress" 1 1
+	check_err $? "Multicast not received on second host"
+
+	delete_mcast_sg $rp1 :: ff0e::3 $rp2 $rp3
+
+	tc filter del dev $h3 ingress protocol ipv6 pref 1 handle 1 flower
+	tc filter del dev $h2 ingress protocol ipv6 pref 1 handle 1 flower
+
+	log_test "Unresolved queue IPv6"
+}
+
 trap cleanup EXIT
 
 setup_prepare