e1000: Hold RTNL when e1000_down can be called

e1000_down calls netif_queue_set_napi, which assumes that RTNL is held.

There are a few paths for e1000_down to be called in e1000 where RTNL is
not currently being held:
  - e1000_shutdown (pci shutdown)
  - e1000_suspend (power management)
  - e1000_reinit_locked (via e1000_reset_task delayed work)
  - e1000_io_error_detected (via pci error handler)

Hold RTNL in three places to fix this issue:
  - e1000_reset_task: igc, igb, and e100e all hold rtnl in this path.
  - e1000_io_error_detected (pci error handler): e1000e and ixgbe hold
    rtnl in this path. A patch has been posted for igc to do the same
    [1].
  - __e1000_shutdown (which is called from both e1000_shutdown and
    e1000_suspend): igb, ixgbe, and e1000e all hold rtnl in the same
    path.

The other paths which call e1000_down seemingly hold RTNL and are OK:
  - e1000_close (ndo_stop)
  - e1000_change_mtu (ndo_change_mtu)

Based on the above analysis and mailing list discussion [2], I believe
adding rtnl in the three places mentioned above is correct.

Fixes: 8f7ff18 ("e1000: Link NAPI instances to queues and IRQs")
Reported-by: Dmitry Antipov <dmantipov@yandex.ru>
Closes: https://lore.kernel.org/netdev/8cf62307-1965-46a0-a411-ff0080090ff9@yandex.ru/
Link: https://lore.kernel.org/netdev/20241022215246.307821-3-jdamato@fastly.com/ [1]
Link: https://lore.kernel.org/netdev/ZxgVRX7Ne-lTjwiJ@LQ3V64L9R2/ [2]
Signed-off-by: Joe Damato <jdamato@fastly.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Author: jdamato-fsly

drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -3509,7 +3509,9 @@ static void e1000_reset_task(struct work_struct *work)
 		container_of(work, struct e1000_adapter, reset_task);
 
 	e_err(drv, "Reset adapter\n");
+	rtnl_lock();
 	e1000_reinit_locked(adapter);
+	rtnl_unlock();
 }
 
 /**
@@ -5074,7 +5076,9 @@ static int __e1000_shutdown(struct pci_dev *pdev, bool *enable_wake)
 			usleep_range(10000, 20000);
 
 		WARN_ON(test_bit(__E1000_RESETTING, &adapter->flags));
+		rtnl_lock();
 		e1000_down(adapter);
+		rtnl_unlock();
 	}
 
 	status = er32(STATUS);
@@ -5235,16 +5239,20 @@ static pci_ers_result_t e1000_io_error_detected(struct pci_dev *pdev,
 	struct net_device *netdev = pci_get_drvdata(pdev);
 	struct e1000_adapter *adapter = netdev_priv(netdev);
 
+	rtnl_lock();
 	netif_device_detach(netdev);
 
-	if (state == pci_channel_io_perm_failure)
+	if (state == pci_channel_io_perm_failure) {
+		rtnl_unlock();
 		return PCI_ERS_RESULT_DISCONNECT;
+	}
 
 	if (netif_running(netdev))
 		e1000_down(adapter);
 
 	if (!test_and_set_bit(__E1000_DISABLED, &adapter->flags))
 		pci_disable_device(pdev);
+	rtnl_unlock();
 
 	/* Request a slot reset. */
 	return PCI_ERS_RESULT_NEED_RESET;