[PATCH 4.6 17/81] team: dont call netdev_change_features under team->lock

Greg Kroah-Hartman
2016-06-22T22:58:28Z

From: Ivan Vecera <ivecera@redhat.com>

[ Upstream commit f6988cb63a4e698d8a62a1d085d263d1fcc351ea ]

The team_device_event() notifier calls team_compute_features() to fix
vlan_features under team->lock to protect team->port_list. The problem is
that subsequent __team_compute_features() calls netdev_change_features()
to propagate vlan_features to upper vlan devices while team->lock is still
taken. This can lead to deadlock when NETIF_F_LRO is modified on lower
devices or team device itself.

Example:
The team0 as active backup with eth0 and eth1 NICs. Both eth0 & eth1 are
LRO capable and LRO is enabled. Thus LRO is also enabled on team0.

The command 'ethtool -K team0 lro off' now hangs due to this deadlock:

dev_ethtool()
-> ethtool_set_features()
-> __netdev_update_features(team)
-> netdev_sync_lower_features()
-> netdev_update_features(lower_1)
-> __netdev_update_features(lower_1)
-> netdev_features_change(lower_1)
-> call_netdevice_notifiers(...)
-> team_device_event(lower_1)
-> team_compute_features(team) [TAKES team->lock]
-> netdev_change_features(team)
-> __netdev_update_features(team)
-> netdev_sync_lower_features()
-> netdev_update_features(lower_2)
-> __netdev_update_features(lower_2)
-> netdev_features_change(lower_2)
-> call_netdevice_notifiers(...)
-> team_device_event(lower_2)
-> team_compute_features(team) [DEADLOCK]

The bug is present in team from the beginning but it appeared after the commit
fd867d5 (net/core: generic support for disabling netdev features down stack)
that adds synchronization of features with lower devices.

Fixes: fd867d5 (net/core: generic support for disabling netdev features down stack)
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/team/team.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/net/team/team.c
+++ b/drivers/net/team/team.c
@@ -990,7 +990,7 @@ static void team_port_disable(struct tea
#define TEAM_ENC_FEATURES (NETIF_F_HW_CSUM | NETIF_F_SG | \
NETIF_F_RXCSUM | NETIF_F_ALL_TSO)

-static void __team_compute_features(struct team *team)
+static void ___team_compute_features(struct team *team)
{
struct team_port *port;
u32 vlan_features = TEAM_VLAN_FEATURES & NETIF_F_ALL_FOR_ALL;
@@ -1021,15 +1021,20 @@ static void __team_compute_features(stru
team->dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
if (dst_release_flag == (IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM))
team->dev->priv_flags |= IFF_XMIT_DST_RELEASE;
+}

+static void __team_compute_features(struct team *team)
+{
+ ___team_compute_features(team);
netdev_change_features(team->dev);
}

static void team_compute_features(struct team *team)
{
mutex_lock(&team->lock);
- __team_compute_features(team);
+ ___team_compute_features(team);
mutex_unlock(&team->lock);
+ netdev_change_features(team->dev);
}

static int team_port_enter(struct team *team, struct team_port *port)