ibmvnic: track pending login

If after ibmvnic sends a LOGIN it gets a FAILOVER, it is possible that
the worker thread will start reset process and free the login response
buffer before it gets a (now stale) LOGIN_RSP. The ibmvnic tasklet will
then try to access the login response buffer and crash.

Have ibmvnic track pending logins and discard any stale login responses.

Fixes: 032c5e8 ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -3841,6 +3841,8 @@ static int send_login(struct ibmvnic_adapter *adapter)
 	crq.login.cmd = LOGIN;
 	crq.login.ioba = cpu_to_be32(buffer_token);
 	crq.login.len = cpu_to_be32(buffer_size);
+
+	adapter->login_pending = true;
 	ibmvnic_send_crq(adapter, &crq);
 
 	return 0;
@@ -4393,6 +4395,15 @@ static int handle_login_rsp(union ibmvnic_crq *login_rsp_crq,
 	u64 *size_array;
 	int i;
 
+	/* CHECK: Test/set of login_pending does not need to be atomic
+	 * because only ibmvnic_tasklet tests/clears this.
+	 */
+	if (!adapter->login_pending) {
+		netdev_warn(netdev, "Ignoring unexpected login response\n");
+		return 0;
+	}
+	adapter->login_pending = false;
+
 	dma_unmap_single(dev, adapter->login_buf_token, adapter->login_buf_sz,
 			 DMA_TO_DEVICE);
 	dma_unmap_single(dev, adapter->login_rsp_buf_token,
@@ -4764,6 +4775,11 @@ static void ibmvnic_handle_crq(union ibmvnic_crq *crq,
 		case IBMVNIC_CRQ_INIT:
 			dev_info(dev, "Partner initialized\n");
 			adapter->from_passive_init = true;
+			/* Discard any stale login responses from prev reset.
+			 * CHECK: should we clear even on INIT_COMPLETE?
+			 */
+			adapter->login_pending = false;
+
 			if (!completion_done(&adapter->init_done)) {
 				complete(&adapter->init_done);
 				adapter->init_done_rc = -EIO;
@@ -5196,6 +5212,7 @@ static int ibmvnic_probe(struct vio_dev *dev, const struct vio_device_id *id)
 	dev_set_drvdata(&dev->dev, netdev);
 	adapter->vdev = dev;
 	adapter->netdev = netdev;
+	adapter->login_pending = false;
 
 	ether_addr_copy(adapter->mac_addr, mac_addr_p);
 	ether_addr_copy(netdev->dev_addr, adapter->mac_addr);

drivers/net/ethernet/ibm/ibmvnic.h

@@ -1086,6 +1086,7 @@ struct ibmvnic_adapter {
 	struct delayed_work ibmvnic_delayed_reset;
 	unsigned long resetting;
 	bool napi_enabled, from_passive_init;
+	bool login_pending;
 
 	bool failover_pending;
 	bool force_reset_recovery;