net: replace dev_addr_sem with netdev instance lock

Lockdep reports possible circular dependency in [0]. Instead of
fixing the ordering, replace global dev_addr_sem with netdev
instance lock. Most of the paths that set/get mac are RTNL
protected. Two places where it's not, convert to explicit
locking:
- sysfs address_show
- dev_get_mac_address via dev_ioctl

0: https://netdev-3.bots.linux.dev/vmksft-forwarding-dbg/results/993321/24-router-bridge-1d-lag-sh/stderr

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250305163732.2766420-12-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index d4ece538f1b23789ca60caa6232690e4d0a4d14a..4382f5e323b065f239227926e2aa66237d793ddf 100644 (file)
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1017,7 +1017,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
                        rtnl_unlock();
                        return -ENOLINK;
                }
-               ret = dev_set_mac_address_user(tap->dev, &sa, NULL);
+               ret = dev_set_mac_address(tap->dev, &sa, NULL);
                tap_put_tap_dev(tap);
                rtnl_unlock();
                return ret;

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index d8f4d3e996a7a81d1f8b04635054081671a14f07..1e645d5e225c0c539a9531062d379f3fab62093d 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -3175,7 +3175,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 
        case SIOCSIFHWADDR:
                /* Set hw address */
-               ret = dev_set_mac_address_user(tun->dev, &ifr.ifr_hwaddr, NULL);
+               ret = dev_set_mac_address(tun->dev, &ifr.ifr_hwaddr, NULL);
                break;
 
        case TUNGETSNDBUF:

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ca9c09dab14e6344a51fa77e109d47ba90e3ee3f..f3e6e6f27e22c9e750e40b087f971f8bb6661b93 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2492,7 +2492,7 @@ struct net_device {
         *
         * Protects:
         *      @gro_flush_timeout, @napi_defer_hard_irqs, @napi_list,
-        *      @net_shaper_hierarchy, @reg_state, @threaded
+        *      @net_shaper_hierarchy, @reg_state, @threaded, @dev_addr
         *
         * Partially protects (writers must hold both @lock and rtnl_lock):
         *      @up
@@ -4262,10 +4262,6 @@ 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);
 int dev_get_port_parent_id(struct net_device *dev,
                           struct netdev_phys_item_id *ppid, bool recurse);

diff --git a/net/core/dev.c b/net/core/dev.c
index 404047d4d94320b8c81a1632dad393c89d3e3d58..a0f75a1d1f5a7244bc82fab5e0545238550cfa16 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1058,6 +1058,28 @@ struct net_device *netdev_get_by_index_lock(struct net *net, int ifindex)
        return __netdev_put_lock(dev);
 }
 
+/**
+ * netdev_get_by_name_lock() - find a device by its name
+ * @net: the applicable net namespace
+ * @name: name of device
+ *
+ * Search for an interface by name. If a valid device
+ * with @name is found it will be returned with netdev->lock held.
+ * netdev_unlock() must be called to release it.
+ *
+ * Return: pointer to a device with lock held, NULL if not found.
+ */
+struct net_device *netdev_get_by_name_lock(struct net *net, const char *name)
+{
+       struct net_device *dev;
+
+       dev = dev_get_by_name(net, name);
+       if (!dev)
+               return NULL;
+
+       return __netdev_put_lock(dev);
+}
+
 struct net_device *
 netdev_xa_find_lock(struct net *net, struct net_device *dev,
                    unsigned long *index)
@@ -9589,44 +9611,24 @@ int netif_set_mac_address(struct net_device *dev, struct sockaddr *sa,
        return 0;
 }
 
-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);
        struct net_device *dev;
-       int ret = 0;
 
-       down_read(&dev_addr_sem);
-       rcu_read_lock();
+       dev = netdev_get_by_name_lock(net, dev_name);
+       if (!dev)
+               return -ENODEV;
 
-       dev = dev_get_by_name_rcu(net, dev_name);
-       if (!dev) {
-               ret = -ENODEV;
-               goto unlock;
-       }
        if (!dev->addr_len)
                memset(sa->sa_data, 0, size);
        else
                memcpy(sa->sa_data, dev->dev_addr,
                       min_t(size_t, size, dev->addr_len));
        sa->sa_family = dev->type;
+       netdev_unlock(dev);
 
-unlock:
-       rcu_read_unlock();
-       up_read(&dev_addr_sem);
-       return ret;
+       return 0;
 }
 EXPORT_SYMBOL(dev_get_mac_address);
 

diff --git a/net/core/dev.h b/net/core/dev.h
index 41b0831aba604447f08af2acadf3a7d1ae9ad574..b50ca645c086349810b6a707a41cb314d89bec75 100644 (file)
--- a/net/core/dev.h
+++ b/net/core/dev.h
@@ -28,6 +28,7 @@ netdev_napi_by_id_lock(struct net *net, unsigned int napi_id);
 struct net_device *dev_get_by_napi_id(unsigned int napi_id);
 
 struct net_device *netdev_get_by_index_lock(struct net *net, int ifindex);
+struct net_device *netdev_get_by_name_lock(struct net *net, const char *name);
 struct net_device *__netdev_put_lock(struct net_device *dev);
 struct net_device *
 netdev_xa_find_lock(struct net *net, struct net_device *dev,
@@ -69,8 +70,6 @@ extern int            weight_p;
 extern int             dev_weight_rx_bias;
 extern int             dev_weight_tx_bias;
 
-extern struct rw_semaphore dev_addr_sem;
-
 /* rtnl helpers */
 extern struct list_head net_todo_list;
 void netdev_run_todo(void);

diff --git a/net/core/dev_api.c b/net/core/dev_api.c
index 98db990ce21ce2a4f2913a8ce5924eac148d4386..655a95fb7baa6dcd3674997ff9e3ebe30ab2d9b8 100644 (file)
--- a/net/core/dev_api.c
+++ b/net/core/dev_api.c
@@ -82,19 +82,6 @@ void dev_set_group(struct net_device *dev, int new_group)
        netdev_unlock_ops(dev);
 }
 
-int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
-                            struct netlink_ext_ack *extack)
-{
-       int ret;
-
-       netdev_lock_ops(dev);
-       ret = netif_set_mac_address_user(dev, sa, extack);
-       netdev_unlock_ops(dev);
-
-       return ret;
-}
-EXPORT_SYMBOL(dev_set_mac_address_user);
-
 /**
  * dev_change_net_namespace() - move device to different nethost namespace
  * @dev: device
@@ -310,9 +297,9 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
 {
        int ret;
 
-       netdev_lock_ops(dev);
+       netdev_lock(dev);
        ret = netif_set_mac_address(dev, sa, extack);
-       netdev_unlock_ops(dev);
+       netdev_unlock(dev);
 
        return ret;
 }

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index d9f35059312108f281d3e8a9403bf1a346a018b7..296e52d1395d66b5fe8be8271f795764897999a7 100644 (file)
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -574,7 +574,7 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, void __user *data,
        case SIOCSIFHWADDR:
                if (dev->addr_len > sizeof(struct sockaddr))
                        return -EINVAL;
-               return dev_set_mac_address_user(dev, &ifr->ifr_hwaddr, NULL);
+               return dev_set_mac_address(dev, &ifr->ifr_hwaddr, NULL);
 
        case SIOCSIFHWBROADCAST:
                if (ifr->ifr_hwaddr.sa_family != dev->type)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 27eea34d1b4162dd40265d8faa44ac023a41d674..02d1d40b47ae3eee5520004b4746093a754d315f 100644 (file)
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -262,14 +262,11 @@ static ssize_t address_show(struct device *dev, struct device_attribute *attr,
        struct net_device *ndev = to_net_dev(dev);
        ssize_t ret = -EINVAL;
 
-       down_read(&dev_addr_sem);
-
-       rcu_read_lock();
+       netdev_lock(ndev);
        if (dev_isalive(ndev))
                ret = sysfs_format_mac(buf, ndev->dev_addr, ndev->addr_len);
-       rcu_read_unlock();
+       netdev_unlock(ndev);
 
-       up_read(&dev_addr_sem);
        return ret;
 }
 static DEVICE_ATTR_RO(address);

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 9d539c9ce1a420b78112f342c81ea0fd17fd9f9f..88a352b02bcef06ac9e028ac90e555a9db44be16 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3089,7 +3089,11 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
                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);
+               if (!netdev_need_ops_lock(dev))
+                       netdev_lock(dev);
+               err = netif_set_mac_address(dev, sa, extack);
+               if (!netdev_need_ops_lock(dev))
+                       netdev_unlock(dev);
                kfree(sa);
                if (err)
                        goto errout;