From bb4c698633c0e19717586a6524a33196cff01a32 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Tue, 24 Feb 2026 14:57:08 +0200 Subject: [PATCH 1/2] team: avoid NETDEV_CHANGEMTU event when unregistering slave syzbot is reporting unregister_netdevice: waiting for netdevsim0 to become free. Usage count = 3 ref_tracker: netdev@ffff88807dcf8618 has 1/2 users at __netdev_tracker_alloc include/linux/netdevice.h:4400 [inline] netdev_hold include/linux/netdevice.h:4429 [inline] inetdev_init+0x201/0x4e0 net/ipv4/devinet.c:286 inetdev_event+0x251/0x1610 net/ipv4/devinet.c:1600 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 call_netdevice_notifiers_mtu net/core/dev.c:2318 [inline] netif_set_mtu_ext+0x5aa/0x800 net/core/dev.c:9886 netif_set_mtu+0xd7/0x1b0 net/core/dev.c:9907 dev_set_mtu+0x126/0x260 net/core/dev_api.c:248 team_port_del+0xb07/0xcb0 drivers/net/team/team_core.c:1333 team_del_slave drivers/net/team/team_core.c:1936 [inline] team_device_event+0x207/0x5b0 drivers/net/team/team_core.c:2929 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2281 [inline] call_netdevice_notifiers net/core/dev.c:2295 [inline] __dev_change_net_namespace+0xcb7/0x2050 net/core/dev.c:12592 do_setlink+0x2ce/0x4590 net/core/rtnetlink.c:3060 rtnl_changelink net/core/rtnetlink.c:3776 [inline] __rtnl_newlink net/core/rtnetlink.c:3935 [inline] rtnl_newlink+0x15a9/0x1be0 net/core/rtnetlink.c:4072 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 problem. Ido Schimmel found steps to reproduce ip link add name team1 type team ip link add name dummy1 mtu 1499 master team1 type dummy ip netns add ns1 ip link set dev dummy1 netns ns1 ip -n ns1 link del dev dummy1 and also found that the same issue was fixed in the bond driver in commit f51048c3e07b ("bonding: avoid NETDEV_CHANGEMTU event when unregistering slave"). Let's do similar thing for the team driver, with commit ad7c7b2172c3 ("net: hold netdev instance lock during sysfs operations") and commit 303a8487a657 ("net: s/__dev_set_mtu/__netif_set_mtu/") also applied. Reported-by: syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84 Suggested-by: Ido Schimmel Reviewed-by: Jiri Pirko Fixes: 3d249d4ca7d0 ("net: introduce ethernet teaming device") Signed-off-by: Tetsuo Handa Signed-off-by: Ido Schimmel Acked-by: Stanislav Fomichev Link: https://patch.msgid.link/20260224125709.317574-2-idosch@nvidia.com Signed-off-by: Jakub Kicinski --- drivers/net/team/team_core.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c index c08a5c1bd6e4..a0fe998cc055 100644 --- a/drivers/net/team/team_core.c +++ b/drivers/net/team/team_core.c @@ -1292,7 +1292,7 @@ err_set_mtu: static void __team_port_change_port_removed(struct team_port *port); -static int team_port_del(struct team *team, struct net_device *port_dev) +static int team_port_del(struct team *team, struct net_device *port_dev, bool unregister) { struct net_device *dev = team->dev; struct team_port *port; @@ -1330,7 +1330,13 @@ static int team_port_del(struct team *team, struct net_device *port_dev) __team_port_change_port_removed(port); team_port_set_orig_dev_addr(port); - dev_set_mtu(port_dev, port->orig.mtu); + if (unregister) { + netdev_lock_ops(port_dev); + __netif_set_mtu(port_dev, port->orig.mtu); + netdev_unlock_ops(port_dev); + } else { + dev_set_mtu(port_dev, port->orig.mtu); + } kfree_rcu(port, rcu); netdev_info(dev, "Port device %s removed\n", portname); netdev_compute_master_upper_features(team->dev, true); @@ -1634,7 +1640,7 @@ static void team_uninit(struct net_device *dev) ASSERT_RTNL(); list_for_each_entry_safe(port, tmp, &team->port_list, list) - team_port_del(team, port->dev); + team_port_del(team, port->dev, false); __team_change_mode(team, NULL); /* cleanup */ __team_options_unregister(team, team_options, ARRAY_SIZE(team_options)); @@ -1933,7 +1939,16 @@ static int team_del_slave(struct net_device *dev, struct net_device *port_dev) ASSERT_RTNL(); - return team_port_del(team, port_dev); + return team_port_del(team, port_dev, false); +} + +static int team_del_slave_on_unregister(struct net_device *dev, struct net_device *port_dev) +{ + struct team *team = netdev_priv(dev); + + ASSERT_RTNL(); + + return team_port_del(team, port_dev, true); } static netdev_features_t team_fix_features(struct net_device *dev, @@ -2926,7 +2941,7 @@ static int team_device_event(struct notifier_block *unused, !!netif_oper_up(port->dev)); break; case NETDEV_UNREGISTER: - team_del_slave(port->team->dev, dev); + team_del_slave_on_unregister(port->team->dev, dev); break; case NETDEV_FEAT_CHANGE: if (!port->team->notifier_ctx) { @@ -2999,3 +3014,4 @@ MODULE_LICENSE("GPL v2"); MODULE_AUTHOR("Jiri Pirko "); MODULE_DESCRIPTION("Ethernet team device driver"); MODULE_ALIAS_RTNL_LINK(DRV_NAME); +MODULE_IMPORT_NS("NETDEV_INTERNAL"); From 58f8ef625e23a607f4a89758d6b328a2701f7354 Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Tue, 24 Feb 2026 14:57:09 +0200 Subject: [PATCH 2/2] selftests: team: Add a reference count leak test Add a test for the issue that was fixed in "team: avoid NETDEV_CHANGEMTU event when unregistering slave". The test hangs due to a reference count leak without the fix: # make -C tools/testing/selftests TARGETS="drivers/net/team" TEST_PROGS=refleak.sh TEST_GEN_PROGS="" run_tests [...] TAP version 13 1..1 # timeout set to 45 # selftests: drivers/net/team: refleak.sh [ 50.681299][ T496] unregister_netdevice: waiting for dummy1 to become free. Usage count = 3 [ 71.185325][ T496] unregister_netdevice: waiting for dummy1 to become free. Usage count = 3 And passes with the fix: # make -C tools/testing/selftests TARGETS="drivers/net/team" TEST_PROGS=refleak.sh TEST_GEN_PROGS="" run_tests [...] TAP version 13 1..1 # timeout set to 45 # selftests: drivers/net/team: refleak.sh ok 1 selftests: drivers/net/team: refleak.sh Signed-off-by: Ido Schimmel Reviewed-by: Jiri Pirko Acked-by: Stanislav Fomichev Link: https://patch.msgid.link/20260224125709.317574-3-idosch@nvidia.com Signed-off-by: Jakub Kicinski --- .../testing/selftests/drivers/net/team/Makefile | 1 + .../selftests/drivers/net/team/refleak.sh | 17 +++++++++++++++++ 2 files changed, 18 insertions(+) create mode 100755 tools/testing/selftests/drivers/net/team/refleak.sh diff --git a/tools/testing/selftests/drivers/net/team/Makefile b/tools/testing/selftests/drivers/net/team/Makefile index 1340b3df9c31..45a3e7ad3dcb 100644 --- a/tools/testing/selftests/drivers/net/team/Makefile +++ b/tools/testing/selftests/drivers/net/team/Makefile @@ -5,6 +5,7 @@ TEST_PROGS := \ dev_addr_lists.sh \ options.sh \ propagation.sh \ + refleak.sh \ # end of TEST_PROGS TEST_INCLUDES := \ diff --git a/tools/testing/selftests/drivers/net/team/refleak.sh b/tools/testing/selftests/drivers/net/team/refleak.sh new file mode 100755 index 000000000000..ef08213ab964 --- /dev/null +++ b/tools/testing/selftests/drivers/net/team/refleak.sh @@ -0,0 +1,17 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# shellcheck disable=SC2154 + +lib_dir=$(dirname "$0") +source "$lib_dir"/../../../net/lib.sh + +trap cleanup_all_ns EXIT + +# Test that there is no reference count leak and that dummy1 can be deleted. +# https://lore.kernel.org/netdev/4d69abe1-ca8d-4f0b-bcf8-13899b211e57@I-love.SAKURA.ne.jp/ +setup_ns ns1 ns2 +ip -n "$ns1" link add name team1 type team +ip -n "$ns1" link add name dummy1 mtu 1499 type dummy +ip -n "$ns1" link set dev dummy1 master team1 +ip -n "$ns1" link set dev dummy1 netns "$ns2" +ip -n "$ns2" link del dev dummy1