net: protect netdev->napi_list with netdev_lock()

Hold netdev->lock when NAPIs are getting added or removed.
This will allow safe access to NAPI instances of a net_device
without rtnl_lock.

Create a family of helpers which assume the lock is already taken.
Switch iavf to them, as it makes extensive use of netdev->lock,
already.

Reviewed-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115035319.559603-6-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c b/drivers/net/ethernet/intel/iavf/iavf_main.c
index ab908d620285c00bdd867e2e63acdf3a839e903b..2db97c5d9f9e60c44080a5e3f5ba6328c5bc8312 100644 (file)
--- a/drivers/net/ethernet/intel/iavf/iavf_main.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
@@ -1800,8 +1800,8 @@ static int iavf_alloc_q_vectors(struct iavf_adapter *adapter)
                q_vector->v_idx = q_idx;
                q_vector->reg_idx = q_idx;
                cpumask_copy(&q_vector->affinity_mask, cpu_possible_mask);
-               netif_napi_add(adapter->netdev, &q_vector->napi,
-                              iavf_napi_poll);
+               netif_napi_add_locked(adapter->netdev, &q_vector->napi,
+                                     iavf_napi_poll);
        }
 
        return 0;
@@ -1827,7 +1827,7 @@ static void iavf_free_q_vectors(struct iavf_adapter *adapter)
        for (q_idx = 0; q_idx < num_q_vectors; q_idx++) {
                struct iavf_q_vector *q_vector = &adapter->q_vectors[q_idx];
 
-               netif_napi_del(&q_vector->napi);
+               netif_napi_del_locked(&q_vector->napi);
        }
        kfree(adapter->q_vectors);
        adapter->q_vectors = NULL;

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cac81b0a166f08015560d06de4bea597dba54a27..3130a8c807dd63c98dd03ebaa5e00595135b3c27 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2456,7 +2456,7 @@ struct net_device {
         * Drivers are free to use it for other protection.
         *
         * Protects:
-        *      @net_shaper_hierarchy, @reg_state
+        *      @napi_list, @net_shaper_hierarchy, @reg_state
         *
         * Partially protects (writers must hold both @lock and rtnl_lock):
         *      @up
@@ -2712,8 +2712,19 @@ static inline void netif_napi_set_irq(struct napi_struct *napi, int irq)
  */
 #define NAPI_POLL_WEIGHT 64
 
-void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
-                          int (*poll)(struct napi_struct *, int), int weight);
+void netif_napi_add_weight_locked(struct net_device *dev,
+                                 struct napi_struct *napi,
+                                 int (*poll)(struct napi_struct *, int),
+                                 int weight);
+
+static inline void
+netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
+                     int (*poll)(struct napi_struct *, int), int weight)
+{
+       netdev_lock(dev);
+       netif_napi_add_weight_locked(dev, napi, poll, weight);
+       netdev_unlock(dev);
+}
 
 /**
  * netif_napi_add() - initialize a NAPI context
@@ -2731,6 +2742,13 @@ netif_napi_add(struct net_device *dev, struct napi_struct *napi,
        netif_napi_add_weight(dev, napi, poll, NAPI_POLL_WEIGHT);
 }
 
+static inline void
+netif_napi_add_locked(struct net_device *dev, struct napi_struct *napi,
+                     int (*poll)(struct napi_struct *, int))
+{
+       netif_napi_add_weight_locked(dev, napi, poll, NAPI_POLL_WEIGHT);
+}
+
 static inline void
 netif_napi_add_tx_weight(struct net_device *dev,
                         struct napi_struct *napi,
@@ -2741,6 +2759,15 @@ netif_napi_add_tx_weight(struct net_device *dev,
        netif_napi_add_weight(dev, napi, poll, weight);
 }
 
+static inline void
+netif_napi_add_config_locked(struct net_device *dev, struct napi_struct *napi,
+                            int (*poll)(struct napi_struct *, int), int index)
+{
+       napi->index = index;
+       napi->config = &dev->napi_config[index];
+       netif_napi_add_weight_locked(dev, napi, poll, NAPI_POLL_WEIGHT);
+}
+
 /**
  * netif_napi_add_config - initialize a NAPI context with persistent config
  * @dev: network device
@@ -2752,9 +2779,9 @@ static inline void
 netif_napi_add_config(struct net_device *dev, struct napi_struct *napi,
                      int (*poll)(struct napi_struct *, int), int index)
 {
-       napi->index = index;
-       napi->config = &dev->napi_config[index];
-       netif_napi_add_weight(dev, napi, poll, NAPI_POLL_WEIGHT);
+       netdev_lock(dev);
+       netif_napi_add_config_locked(dev, napi, poll, index);
+       netdev_unlock(dev);
 }
 
 /**
@@ -2774,6 +2801,8 @@ static inline void netif_napi_add_tx(struct net_device *dev,
        netif_napi_add_tx_weight(dev, napi, poll, NAPI_POLL_WEIGHT);
 }
 
+void __netif_napi_del_locked(struct napi_struct *napi);
+
 /**
  *  __netif_napi_del - remove a NAPI context
  *  @napi: NAPI context
@@ -2782,7 +2811,18 @@ static inline void netif_napi_add_tx(struct net_device *dev,
  * containing @napi. Drivers might want to call this helper to combine
  * all the needed RCU grace periods into a single one.
  */
-void __netif_napi_del(struct napi_struct *napi);
+static inline void __netif_napi_del(struct napi_struct *napi)
+{
+       netdev_lock(napi->dev);
+       __netif_napi_del_locked(napi);
+       netdev_unlock(napi->dev);
+}
+
+static inline void netif_napi_del_locked(struct napi_struct *napi)
+{
+       __netif_napi_del_locked(napi);
+       synchronize_net();
+}
 
 /**
  *  netif_napi_del - remove a NAPI context

diff --git a/net/core/dev.c b/net/core/dev.c
index 65bf95593da7d3a14c91e9f9dcda6ae565dada78..235707c0f631ba64dddc34089db5b6372457c77f 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6910,9 +6910,12 @@ netif_napi_dev_list_add(struct net_device *dev, struct napi_struct *napi)
        list_add_rcu(&napi->dev_list, higher); /* adds after higher */
 }
 
-void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
-                          int (*poll)(struct napi_struct *, int), int weight)
+void netif_napi_add_weight_locked(struct net_device *dev,
+                                 struct napi_struct *napi,
+                                 int (*poll)(struct napi_struct *, int),
+                                 int weight)
 {
+       netdev_assert_locked(dev);
        if (WARN_ON(test_and_set_bit(NAPI_STATE_LISTED, &napi->state)))
                return;
 
@@ -6953,7 +6956,7 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
                dev->threaded = false;
        netif_napi_set_irq(napi, -1);
 }
-EXPORT_SYMBOL(netif_napi_add_weight);
+EXPORT_SYMBOL(netif_napi_add_weight_locked);
 
 void napi_disable(struct napi_struct *n)
 {
@@ -7024,8 +7027,10 @@ static void flush_gro_hash(struct napi_struct *napi)
 }
 
 /* Must be called in process context */
-void __netif_napi_del(struct napi_struct *napi)
+void __netif_napi_del_locked(struct napi_struct *napi)
 {
+       netdev_assert_locked(napi->dev);
+
        if (!test_and_clear_bit(NAPI_STATE_LISTED, &napi->state))
                return;
 
@@ -7045,7 +7050,7 @@ void __netif_napi_del(struct napi_struct *napi)
                napi->thread = NULL;
        }
 }
-EXPORT_SYMBOL(__netif_napi_del);
+EXPORT_SYMBOL(__netif_napi_del_locked);
 
 static int __napi_poll(struct napi_struct *n, bool *repoll)
 {