[PATCH 5.15 047/135] net: Write lock dev_base_lock without disabling bottom halves.

Greg Kroah-Hartman
2022-06-27T11:39:27Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

[ Upstream commit fd888e85fe6b661e78044dddfec0be5271afa626 ]

The writer acquires dev_base_lock with disabled bottom halves.
The reader can acquire dev_base_lock without disabling bottom halves
because there is no writer in softirq context.

On PREEMPT_RT the softirqs are preemptible and local_bh_disable() acts
as a lock to ensure that resources, that are protected by disabling
bottom halves, remain protected.
This leads to a circular locking dependency if the lock acquired with
disabled bottom halves (as in write_lock_bh()) and somewhere else with
enabled bottom halves (as by read_lock() in netstat_show()) followed by
disabling bottom halves (cxgb_get_stats() -> t4_wr_mbox_meat_timeout()
-> spin_lock_bh()). This is the reverse locking order.

All read_lock() invocation are from sysfs callback which are not invoked
from softirq context. Therefore there is no need to disable bottom
halves while acquiring a write lock.

Acquire the write lock of dev_base_lock without disabling bottom halves.

Reported-by: Pei Zhang <pezhang@redhat.com>
Reported-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/dev.c | 16 ++++++++--------
net/core/link_watch.c | 4 ++--
net/core/rtnetlink.c | 8 ++++----
net/hsr/hsr_device.c | 6 +++---
4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index b9731b267d07..860fc6a98373 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -365,12 +365,12 @@ static void list_netdevice(struct net_device *dev)

ASSERT_RTNL();

- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);
list_add_tail_rcu(&dev->dev_list, &net->dev_base_head);
netdev_name_node_add(net, dev->name_node);
hlist_add_head_rcu(&dev->index_hlist,
dev_index_hash(net, dev->ifindex));
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);

dev_base_seq_inc(net);
}
@@ -383,11 +383,11 @@ static void unlist_netdevice(struct net_device *dev)
ASSERT_RTNL();

/* Unlink dev from the device chain */
- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);
list_del_rcu(&dev->dev_list);
netdev_name_node_del(dev->name_node);
hlist_del_rcu(&dev->index_hlist);
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);

dev_base_seq_inc(dev_net(dev));
}
@@ -1266,15 +1266,15 @@ int dev_change_name(struct net_device *dev, const char *newname)

netdev_adjacent_rename_links(dev, oldname);

- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);
netdev_name_node_del(dev->name_node);
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);

synchronize_rcu();

- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);
netdev_name_node_add(net, dev->name_node);
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);

ret = call_netdevice_notifiers(NETDEV_CHANGENAME, dev);
ret = notifier_to_errno(ret);
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 1a455847da54..9599afd0862d 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -55,7 +55,7 @@ static void rfc2863_policy(struct net_device *dev)
if (operstate == dev->operstate)
return;

- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);

switch(dev->link_mode) {
case IF_LINK_MODE_TESTING:
@@ -74,7 +74,7 @@ static void rfc2863_policy(struct net_device *dev)

dev->operstate = operstate;

- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);
}

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 9c0e8ccf9bc5..8c85e93daa73 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -842,9 +842,9 @@ static void set_operstate(struct net_device *dev, unsigned char transition)
}

if (dev->operstate != operstate) {
- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);
dev->operstate = operstate;
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);
netdev_state_change(dev);
}
}
@@ -2781,11 +2781,11 @@ static int do_setlink(const struct sk_buff *skb,
if (tb[IFLA_LINKMODE]) {
unsigned char value = nla_get_u8(tb[IFLA_LINKMODE]);

- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);
if (dev->link_mode ^ value)
status |= DO_SETLINK_NOTIFY;
dev->link_mode = value;
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);
}

if (tb[IFLA_VFINFO_LIST]) {
diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index 26c32407f029..ea7b96e296ef 100644
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c
@@ -30,13 +30,13 @@ static bool is_slave_up(struct net_device *dev)

static void __hsr_set_operstate(struct net_device *dev, int transition)
{
- write_lock_bh(&dev_base_lock);
+ write_lock(&dev_base_lock);
if (dev->operstate != transition) {
dev->operstate = transition;
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);
netdev_state_change(dev);
} else {
- write_unlock_bh(&dev_base_lock);
+ write_unlock(&dev_base_lock);
}
}

--
2.35.1