Re: [PATCH net v2] team: don't call netdev_change_features under team->lock

2016-05-25 Thread David Miller 
From: Ivan Vecera 
Date: Wed, 25 May 2016 21:21:52 +0200

> 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:
 ...
> 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 
> Signed-off-by: Ivan Vecera 

Applied and queued up for -stable, thanks.

Re: [PATCH net v2] team: don't call netdev_change_features under team->lock

2016-05-25 Thread Jiri Pirko 
Wed, May 25, 2016 at 09:21:52PM CEST, ivec...@redhat.com wrote:
>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 
>Signed-off-by: Ivan Vecera 

Signed-off-by: Jiri Pirko

[PATCH net v2] team: don't call netdev_change_features under team->lock

2016-05-25 Thread Ivan Vecera 
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 
Signed-off-by: Ivan Vecera 
---
 drivers/net/team/team.c | 9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
index 718ceea..800a449 100644
--- a/drivers/net/team/team.c
+++ b/drivers/net/team/team.c
@@ -988,7 +988,7 @@ 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;
@@ -1019,15 +1019,20 @@ 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)
-- 
2.7.3