wifi: iwlwifi: pcie: allocate dummy net_device dynamically

struct net_device shouldn't be embedded into any structure, instead,
the owner should use the priv space to embed their state into net_device.

Embedding net_device into structures prohibits the usage of flexible
arrays in the net_device structure. For more details, see the discussion
at [1].

Un-embed the net_device from struct iwl_trans_pcie by converting it
into a pointer. Then use the leverage alloc_netdev() to allocate the
net_device object at iwl_trans_pcie_alloc.

The private data of net_device becomes a pointer for the struct
iwl_trans_pcie, so, it is easy to get back to the iwl_trans_pcie parent
given the net_device object.

[1] https://lore.kernel.org/all/20240229225910.79e224cf@kernel.org/Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://msgid.link/20240501165417.3406039-1-leitao@debian.orgSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/pcie/internal.h

@@ -386,7 +386,7 @@ struct iwl_trans_pcie {
 	dma_addr_t iml_dma_addr;
 	struct iwl_trans *trans;
 
-	struct net_device napi_dev;
+	struct net_device *napi_dev;
 
 	/* INT ICT Table */
 	__le32 *ict_tbl;

drivers/net/wireless/intel/iwlwifi/pcie/rx.c

@@ -1000,6 +1000,11 @@ void iwl_pcie_rx_init_rxb_lists(struct iwl_rxq *rxq)
 
 static int iwl_pcie_rx_handle(struct iwl_trans *trans, int queue, int budget);
 
+static inline struct iwl_trans_pcie *iwl_netdev_to_trans_pcie(struct net_device *dev)
+{
+	return *(struct iwl_trans_pcie **)netdev_priv(dev);
+}
+
 static int iwl_pcie_napi_poll(struct napi_struct *napi, int budget)
 {
 	struct iwl_rxq *rxq = container_of(napi, struct iwl_rxq, napi);
@@ -1007,7 +1012,7 @@ static int iwl_pcie_napi_poll(struct napi_struct *napi, int budget)
 	struct iwl_trans *trans;
 	int ret;
 
-	trans_pcie = container_of(napi->dev, struct iwl_trans_pcie, napi_dev);
+	trans_pcie = iwl_netdev_to_trans_pcie(napi->dev);
 	trans = trans_pcie->trans;
 
 	ret = iwl_pcie_rx_handle(trans, rxq->id, budget);
@@ -1034,7 +1039,7 @@ static int iwl_pcie_napi_poll_msix(struct napi_struct *napi, int budget)
 	struct iwl_trans *trans;
 	int ret;
 
-	trans_pcie = container_of(napi->dev, struct iwl_trans_pcie, napi_dev);
+	trans_pcie = iwl_netdev_to_trans_pcie(napi->dev);
 	trans = trans_pcie->trans;
 
 	ret = iwl_pcie_rx_handle(trans, rxq->id, budget);
@@ -1131,7 +1136,7 @@ static int _iwl_pcie_rx_init(struct iwl_trans *trans)
 			if (trans_pcie->msix_enabled)
 				poll = iwl_pcie_napi_poll_msix;
 
-			netif_napi_add(&trans_pcie->napi_dev, &rxq->napi,
+			netif_napi_add(trans_pcie->napi_dev, &rxq->napi,
 				       poll);
 			napi_enable(&rxq->napi);
 		}

drivers/net/wireless/intel/iwlwifi/pcie/trans.c

@@ -1986,13 +1986,6 @@ static void iwl_trans_pcie_configure(struct iwl_trans *trans,
 	trans->command_groups = trans_cfg->command_groups;
 	trans->command_groups_size = trans_cfg->command_groups_size;
 
-	/* Initialize NAPI here - it should be before registering to mac80211
-	 * in the opmode but after the HW struct is allocated.
-	 * As this function may be called again in some corner cases don't
-	 * do anything if NAPI was already initialized.
-	 */
-	if (trans_pcie->napi_dev.reg_state != NETREG_DUMMY)
-		init_dummy_netdev(&trans_pcie->napi_dev);
 
 	trans_pcie->fw_reset_handshake = trans_cfg->fw_reset_handshake;
 }
@@ -2074,6 +2067,8 @@ void iwl_trans_pcie_free(struct iwl_trans *trans)
 		iwl_pcie_free_ict(trans);
 	}
 
+	free_netdev(trans_pcie->napi_dev);
+
 	iwl_pcie_free_invalid_tx_cmd(trans);
 
 	iwl_pcie_free_fw_monitor(trans);
@@ -3594,7 +3589,7 @@ struct iwl_trans *iwl_trans_pcie_alloc(struct pci_dev *pdev,
 			       const struct pci_device_id *ent,
 			       const struct iwl_cfg_trans_params *cfg_trans)
 {
-	struct iwl_trans_pcie *trans_pcie;
+	struct iwl_trans_pcie *trans_pcie, **priv;
 	struct iwl_trans *trans;
 	int ret, addr_size;
 	const struct iwl_trans_ops *ops = &trans_ops_pcie_gen2;
@@ -3623,6 +3618,18 @@ struct iwl_trans *iwl_trans_pcie_alloc(struct pci_dev *pdev,
 
 	trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 
+	/* Initialize NAPI here - it should be before registering to mac80211
+	 * in the opmode but after the HW struct is allocated.
+	 */
+	trans_pcie->napi_dev = alloc_netdev_dummy(sizeof(struct iwl_trans_pcie *));
+	if (!trans_pcie->napi_dev) {
+		ret = -ENOMEM;
+		goto out_free_trans;
+	}
+	/* The private struct in netdev is a pointer to struct iwl_trans_pcie */
+	priv = netdev_priv(trans_pcie->napi_dev);
+	*priv = trans_pcie;
+
 	trans_pcie->trans = trans;
 	trans_pcie->opmode_down = true;
 	spin_lock_init(&trans_pcie->irq_lock);
@@ -3637,7 +3644,7 @@ struct iwl_trans *iwl_trans_pcie_alloc(struct pci_dev *pdev,
 						   WQ_HIGHPRI | WQ_UNBOUND, 0);
 	if (!trans_pcie->rba.alloc_wq) {
 		ret = -ENOMEM;
-		goto out_free_trans;
+		goto out_free_ndev;
 	}
 	INIT_WORK(&trans_pcie->rba.rx_alloc, iwl_pcie_rx_allocator_work);
 
@@ -3757,6 +3764,8 @@ struct iwl_trans *iwl_trans_pcie_alloc(struct pci_dev *pdev,
 	iwl_pcie_free_ict(trans);
 out_no_pci:
 	destroy_workqueue(trans_pcie->rba.alloc_wq);
+out_free_ndev:
+	free_netdev(trans_pcie->napi_dev);
 out_free_trans:
 	iwl_trans_free(trans);
 	return ERR_PTR(ret);