Merge branch 'bridge-mcast-fix-a-possible-use-after-free-when-removing-a-bridge-port'

Ido Schimmel says:

====================
bridge: mcast: Fix a possible use-after-free when removing a bridge port

Patch #1 fixes a possible use-after-free when removing a bridge port.

Patch #2 adds a test case that triggers the problem.

In net-next we can:

1. Add DEBUG_NET_WARN_ON_ONCE() when a port multicast context is
de-initialized while enabled.

2. When de-initializing a port multicast context, synchronously shutdown
all the timers that were initialized when the context was initialized.
====================

Link: https://patch.msgid.link/20260517121122.188333-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 46 insertions, 6 deletions

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 881d866d687a..2eef4f3345cd 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -4640,10 +4640,24 @@ static void br_multicast_start_querier(struct net_bridge_mcast *brmctx,
 	rcu_read_unlock();
 }
 
-static void br_multicast_del_grps(struct net_bridge *br)
+static void br_multicast_enable_all_ports(struct net_bridge *br)
 {
 	struct net_bridge_port *port;
 
+	if (br_opt_get(br, BROPT_MCAST_VLAN_SNOOPING_ENABLED))
+		return;
+
+	list_for_each_entry(port, &br->port_list, list)
+		__br_multicast_enable_port_ctx(&port->multicast_ctx);
+}
+
+static void br_multicast_disable_all_ports(struct net_bridge *br)
+{
+	struct net_bridge_port *port;
+
+	if (br_opt_get(br, BROPT_MCAST_VLAN_SNOOPING_ENABLED))
+		return;
+
 	list_for_each_entry(port, &br->port_list, list)
 		__br_multicast_disable_port_ctx(&port->multicast_ctx);
 }
@@ -4651,7 +4665,6 @@ static void br_multicast_del_grps(struct net_bridge *br)
 int br_multicast_toggle(struct net_bridge *br, unsigned long val,
 			struct netlink_ext_ack *extack)
 {
-	struct net_bridge_port *port;
 	bool change_snoopers = false;
 	int err = 0;
 
@@ -4668,7 +4681,7 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val,
 	br_opt_toggle(br, BROPT_MULTICAST_ENABLED, !!val);
 	if (!br_opt_get(br, BROPT_MULTICAST_ENABLED)) {
 		change_snoopers = true;
-		br_multicast_del_grps(br);
+		br_multicast_disable_all_ports(br);
 		goto unlock;
 	}
 
@@ -4676,8 +4689,7 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val,
 		goto unlock;
 
 	br_multicast_open(br);
-	list_for_each_entry(port, &br->port_list, list)
-		__br_multicast_enable_port_ctx(&port->multicast_ctx);
+	br_multicast_enable_all_ports(br);
 
 	change_snoopers = true;
 
diff --git a/tools/testing/selftests/net/forwarding/bridge_vlan_mcast.sh b/tools/testing/selftests/net/forwarding/bridge_vlan_mcast.sh
index e8031f68200a..ebdb4c790a5d 100755
--- a/tools/testing/selftests/net/forwarding/bridge_vlan_mcast.sh
+++ b/tools/testing/selftests/net/forwarding/bridge_vlan_mcast.sh
@@ -4,7 +4,7 @@
 ALL_TESTS="vlmc_control_test vlmc_querier_test vlmc_igmp_mld_version_test \
 	   vlmc_last_member_test vlmc_startup_query_test vlmc_membership_test \
 	   vlmc_querier_intvl_test vlmc_query_intvl_test vlmc_query_response_intvl_test \
-	   vlmc_router_port_test vlmc_filtering_test"
+	   vlmc_router_port_test vlmc_filtering_test vlmc_mcast_toggle_test"
 NUM_NETIFS=4
 CHECK_TC="yes"
 TEST_GROUP="239.10.10.10"
@@ -537,6 +537,34 @@ vlmc_filtering_test()
 	log_test "Disable multicast vlan snooping when vlan filtering is disabled"
 }
 
+vlmc_mcast_toggle_test()
+{
+	RET=0
+
+	ip link add name br1-mcast up type bridge mcast_snooping 1 mcast_querier 1 vlan_filtering 1
+	ip link add name dummy1-mcast up master br1-mcast type dummy
+
+	# Enabling per-VLAN multicast snooping should disable the per-port
+	# multicast context on "dummy1-mcast".
+	ip link set dev br1-mcast type bridge mcast_vlan_snooping 1
+
+	# Toggling multicast snooping on the bridge should not affect the
+	# per-port multicast context on "dummy1-mcast" given that per-VLAN
+	# multicast snooping is enabled.
+	ip link set dev br1-mcast type bridge mcast_snooping 0
+	ip link set dev br1-mcast type bridge mcast_snooping 1
+
+	# If both the per-port and per-{port, VLAN} multicast contexts are
+	# enabled on "dummy1-mcast", removing it from the bridge will result
+	# in a splat.
+	ip link set dev dummy1-mcast nomaster
+
+	log_test "Toggling mcast snooping with per-VLAN mcast snooping enabled"
+
+	ip link del dev dummy1-mcast
+	ip link del dev br1-mcast
+}
+
 trap cleanup EXIT
 
 setup_prepare