Merge branch 'net-use-netdev-lock-to-protect-napi'

Jakub Kicinski says:

====================
net: use netdev->lock to protect NAPI

We recently added a lock member to struct net_device, with a vague
plan to start using it to protect netdev-local state, removing
the need to take rtnl_lock for new configuration APIs.

Lay some groundwork and use this lock for protecting NAPI APIs.

v1: https://lore.kernel.org/20250114035118.110297-1-kuba@kernel.org
====================

Link: https://patch.msgid.link/20250115035319.559603-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 35 insertions, 4 deletions

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 2d9afc6e2161..07cb99b114bd 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -36,7 +36,7 @@ static const char fmt_uint[] = "%u\n";
 static const char fmt_ulong[] = "%lu\n";
 static const char fmt_u64[] = "%llu\n";
 
-/* Caller holds RTNL or RCU */
+/* Caller holds RTNL, netdev->lock or RCU */
 static inline int dev_isalive(const struct net_device *dev)
 {
 	return READ_ONCE(dev->reg_state) <= NETREG_REGISTERED;
@@ -108,6 +108,36 @@ static ssize_t netdev_store(struct device *dev, struct device_attribute *attr,
 	return ret;
 }
 
+/* Same as netdev_store() but takes netdev_lock() instead of rtnl_lock() */
+static ssize_t
+netdev_lock_store(struct device *dev, struct device_attribute *attr,
+		  const char *buf, size_t len,
+		  int (*set)(struct net_device *, unsigned long))
+{
+	struct net_device *netdev = to_net_dev(dev);
+	struct net *net = dev_net(netdev);
+	unsigned long new;
+	int ret;
+
+	if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+		return -EPERM;
+
+	ret = kstrtoul(buf, 0, &new);
+	if (ret)
+		return ret;
+
+	netdev_lock(netdev);
+
+	if (dev_isalive(netdev)) {
+		ret = (*set)(netdev, new);
+		if (ret == 0)
+			ret = len;
+	}
+	netdev_unlock(netdev);
+
+	return ret;
+}
+
 NETDEVICE_SHOW_RO(dev_id, fmt_hex);
 NETDEVICE_SHOW_RO(dev_port, fmt_dec);
 NETDEVICE_SHOW_RO(addr_assign_type, fmt_dec);
@@ -420,7 +450,7 @@ static ssize_t gro_flush_timeout_store(struct device *dev,
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
 
-	return netdev_store(dev, attr, buf, len, change_gro_flush_timeout);
+	return netdev_lock_store(dev, attr, buf, len, change_gro_flush_timeout);
 }
 NETDEVICE_SHOW_RW(gro_flush_timeout, fmt_ulong);
 
@@ -440,7 +470,8 @@ static ssize_t napi_defer_hard_irqs_store(struct device *dev,
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
 
-	return netdev_store(dev, attr, buf, len, change_napi_defer_hard_irqs);
+	return netdev_lock_store(dev, attr, buf, len,
+				 change_napi_defer_hard_irqs);
 }
 NETDEVICE_SHOW_RW(napi_defer_hard_irqs, fmt_uint);
 
@@ -638,7 +669,7 @@ static ssize_t threaded_store(struct device *dev,
 			      struct device_attribute *attr,
 			      const char *buf, size_t len)
 {
-	return netdev_store(dev, attr, buf, len, modify_napi_threaded);
+	return netdev_lock_store(dev, attr, buf, len, modify_napi_threaded);
 }
 static DEVICE_ATTR_RW(threaded);