linux-kernel - [PATCH net-next 2/2] net: reorder dev_addr

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Message-ID: <20250311084507.3978048-3-sdf@fomichev.me>
Date: Tue, 11 Mar 2025 01:45:07 -0700
From: Stanislav Fomichev <sdf@...ichev.me>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	linux-kernel@...r.kernel.org,
	willemdebruijn.kernel@...il.com,
	jasowang@...hat.com,
	andrew+netdev@...n.ch,
	horms@...nel.org,
	sdf@...ichev.me,
	jdamato@...tly.com,
	kory.maincent@...tlin.com,
	atenart@...nel.org,
	kuniyu@...zon.com,
	Kohei Enju <enjuk@...zon.com>
Subject: [PATCH net-next 2/2] net: reorder dev_addr_sem lock

Lockdep complains about circular lock in 1 -> 2 -> 3 (see below).

Change the lock ordering to be:
- rtnl_lock
- dev_addr_sem
- netdev_ops (only for lower devices!)
- team_lock (or other per-upper device lock)

1. rtnl_lock -> netdev_ops -> dev_addr_sem

rtnl_setlink
  rtnl_lock
    do_setlink IFLA_ADDRESS on lower
      netdev_ops
        dev_addr_sem

2. rtnl_lock -> team_lock -> netdev_ops

rtnl_newlink
  rtnl_lock
    do_setlink IFLA_MASTER on lower
      do_set_master
        team_add_slave
          team_lock
            team_port_add
	      dev_set_mtu
	        netdev_ops

3. rtnl_lock -> dev_addr_sem -> team_lock

rtnl_newlink
  rtnl_lock
    do_setlink IFLA_ADDRESS on upper
      dev_addr_sem
        netif_set_mac_address
          team_set_mac_address
            team_lock

4. rtnl_lock -> netdev_ops -> dev_addr_sem

rtnl_lock
  dev_ifsioc
    dev_set_mac_address_user

__tun_chr_ioctl
  rtnl_lock
    dev_set_mac_address_user

tap_ioctl
  rtnl_lock
    dev_set_mac_address_user

dev_set_mac_address_user
  netdev_lock_ops
    netif_set_mac_address_user
      dev_addr_sem

Cc: Kohei Enju <enjuk@...zon.com>
Fixes: df43d8bf1031 ("net: replace dev_addr_sem with netdev instance lock")
Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
---
 include/linux/netdevice.h |  2 --
 net/core/dev.c            | 11 -----------
 net/core/dev_api.c        |  4 +++-
 net/core/rtnetlink.c      | 15 +++++++++++++--
 4 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 42c75cb028e7..2bf1f914f61a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4198,8 +4198,6 @@ int netif_set_mac_address(struct net_device *dev, struct sockaddr *sa,
 			  struct netlink_ext_ack *extack);
 int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
 			struct netlink_ext_ack *extack);
-int netif_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
-			       struct netlink_ext_ack *extack);
 int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
 			     struct netlink_ext_ack *extack);
 int dev_get_mac_address(struct sockaddr *sa, struct net *net, char *dev_name);
diff --git a/net/core/dev.c b/net/core/dev.c
index 5a64389461e2..66290c159ad8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9592,17 +9592,6 @@ int netif_set_mac_address(struct net_device *dev, struct sockaddr *sa,
 
 DECLARE_RWSEM(dev_addr_sem);
 
-int netif_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
-			       struct netlink_ext_ack *extack)
-{
-	int ret;
-
-	down_write(&dev_addr_sem);
-	ret = netif_set_mac_address(dev, sa, extack);
-	up_write(&dev_addr_sem);
-	return ret;
-}
-
 int dev_get_mac_address(struct sockaddr *sa, struct net *net, char *dev_name)
 {
 	size_t size = sizeof(sa->sa_data_min);
diff --git a/net/core/dev_api.c b/net/core/dev_api.c
index 2e17548af685..8dbc60612100 100644
--- a/net/core/dev_api.c
+++ b/net/core/dev_api.c
@@ -89,9 +89,11 @@ int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
 {
 	int ret;
 
+	down_write(&dev_addr_sem);
 	netdev_lock_ops(dev);
-	ret = netif_set_mac_address_user(dev, sa, extack);
+	ret = netif_set_mac_address(dev, sa, extack);
 	netdev_unlock_ops(dev);
+	up_write(&dev_addr_sem);
 
 	return ret;
 }
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 9355058bf996..c9d44dad203d 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3080,21 +3080,32 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
 		struct sockaddr *sa;
 		int len;
 
+		netdev_unlock_ops(dev);
+
+		/* dev_addr_sem is an outer lock, enforce proper ordering */
+		down_write(&dev_addr_sem);
+		netdev_lock_ops(dev);
+
 		len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
 						  sizeof(*sa));
 		sa = kmalloc(len, GFP_KERNEL);
 		if (!sa) {
+			up_write(&dev_addr_sem);
 			err = -ENOMEM;
 			goto errout;
 		}
 		sa->sa_family = dev->type;
 		memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
 		       dev->addr_len);
-		err = netif_set_mac_address_user(dev, sa, extack);
+		err = netif_set_mac_address(dev, sa, extack);
 		kfree(sa);
-		if (err)
+		if (err) {
+			up_write(&dev_addr_sem);
 			goto errout;
+		}
 		status |= DO_SETLINK_MODIFIED;
+
+		up_write(&dev_addr_sem);
 	}
 
 	if (tb[IFLA_MTU]) {
-- 
2.48.1