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team: don't call netdev_change_features under team->lock 

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>
This commit is contained in:
Ivan Vecera 2016-05-25 21:21:52 +02:00 committed by David S. Miller
parent f58fb33012
commit f6988cb63a
1 changed files with 7 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/net/team/team.c
View File

@ -990,7 +990,7 @@ static void team_port_disable(struct team *team,
#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(struct team *team)
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)