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net: Write lock dev_base_lock without disabling bottom halves.

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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>
This commit is contained in:
Sebastian Andrzej Siewior
2021-11-26 17:15:29 +01:00
committed by David S. Miller
parent 07b8ca3792
commit fd888e85fe
4 changed files with 17 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
net/core/dev.c
View File

@ -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));
}
@ -1188,15 +1188,15 @@ rollback:
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);