From 87b3f4f3bfd48c4e950df544cac8fa34ecaba0d5 Mon Sep 17 00:00:00 2001
From: Ivan Vecera <ivecera@redhat.com>
Date: Mon, 25 Jan 2021 08:44:16 +0100
Subject: [PATCH 12/12] team: protect features update by RCU to avoid deadlock
Git-commit: f0947d0d21b219e03940b9be6628a43445c0de7a
Patch-mainline: v5.11-rc6
References: git-fixes
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: Denis Kirjanov <denis.kirjanov@suse.com>
---
drivers/net/team/team.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
index 3c45a47fd813..2d2dbb19cb31 100644
--- a/drivers/net/team/team.c
+++ b/drivers/net/team/team.c
@@ -1002,7 +1002,8 @@ static void __team_compute_features(struct team *team)
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);
@@ -1016,6 +1017,7 @@ static void __team_compute_features(struct team *team)
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 |
@@ -1031,9 +1033,7 @@ static void __team_compute_features(struct team *team)
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);
}
--
2.16.4