From: Ivan Vecera ivecera@redhat.com
commit f0947d0d21b219e03940b9be6628a43445c0de7a upstream.
Function __team_compute_features() is protected by team->lock mutex when it is called from team_compute_features() used when features of an underlying device is changed. This causes a deadlock when NETDEV_FEAT_CHANGE notifier for underlying device is fired due to change propagated from team driver (e.g. MTU change). It's because callbacks like team_change_mtu() or team_vlan_rx_{add,del}_vid() protect their port list traversal by team->lock mutex.
Example (r8169 case where this driver disables TSO for certain MTU values): ... [ 6391.348202] __mutex_lock.isra.6+0x2d0/0x4a0 [ 6391.358602] team_device_event+0x9d/0x160 [team] [ 6391.363756] notifier_call_chain+0x47/0x70 [ 6391.368329] netdev_update_features+0x56/0x60 [ 6391.373207] rtl8169_change_mtu+0x14/0x50 [r8169] [ 6391.378457] dev_set_mtu_ext+0xe1/0x1d0 [ 6391.387022] dev_set_mtu+0x52/0x90 [ 6391.390820] team_change_mtu+0x64/0xf0 [team] [ 6391.395683] dev_set_mtu_ext+0xe1/0x1d0 [ 6391.399963] do_setlink+0x231/0xf50 ...
In fact team_compute_features() called from team_device_event() does not need to be protected by team->lock mutex and rcu_read_lock() is sufficient there for port list traversal.
Fixes: 3d249d4ca7d0 ("net: introduce ethernet teaming device") Cc: Saeed Mahameed saeed@kernel.org Signed-off-by: Ivan Vecera ivecera@redhat.com Reviewed-by: Cong Wang xiyou.wangcong@gmail.com Reviewed-by: Jiri Pirko jiri@nvidia.com Link: https://lore.kernel.org/r/20210125074416.4056484-1-ivecera@redhat.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/net/team/team.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/net/team/team.c +++ b/drivers/net/team/team.c @@ -991,7 +991,8 @@ static void __team_compute_features(stru unsigned int dst_release_flag = IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM;
- list_for_each_entry(port, &team->port_list, list) { + rcu_read_lock(); + list_for_each_entry_rcu(port, &team->port_list, list) { vlan_features = netdev_increment_features(vlan_features, port->dev->vlan_features, TEAM_VLAN_FEATURES); @@ -1005,6 +1006,7 @@ static void __team_compute_features(stru if (port->dev->hard_header_len > max_hard_header_len) max_hard_header_len = port->dev->hard_header_len; } + rcu_read_unlock();
team->dev->vlan_features = vlan_features; team->dev->hw_enc_features = enc_features | NETIF_F_GSO_ENCAP_ALL | @@ -1020,9 +1022,7 @@ static void __team_compute_features(stru
static void team_compute_features(struct team *team) { - mutex_lock(&team->lock); __team_compute_features(team); - mutex_unlock(&team->lock); netdev_change_features(team->dev); }