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

[Greg Kroah-Hartman]

From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

[ 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@xxxxxxxxxx>
Reported-by: Luis Claudio R. Goncalves <lgoncalv@xxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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