Re: [RFC PATCH v2] e1000e: Use rtnl_lock to prevent race conditions between net and pci/pm

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

Hi Greg,

> On Oct 8, 2019, at 01:27, Alexander Duyck <alexander.duyck@gmail.com> wrote:
> 
> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> 
> This patch is meant to address possible race conditions that can exist
> between network configuration and power management. A similar issue was
> fixed for igb in commit 9474933caf21 ("igb: close/suspend race in
> netif_device_detach").
> 
> In addition it consolidates the code so that the PCI error handling code
> will essentially perform the power management freeze on the device prior to
> attempting a reset, and will thaw the device afterwards if that is what it
> is planning to do. Otherwise when we call close on the interface it should
> see it is detached and not attempt to call the logic to down the interface
> and free the IRQs again.
> 
>> From what I can tell the check that was adding the check for __E1000_DOWN
> in e1000e_close was added when runtime power management was added. However
> it should not be relevant for us as we perform a call to
> pm_runtime_get_sync before we call e1000_down/free_irq so it should always
> be back up before we call into this anyway.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>

Please merge this commit, a7023819404ac9bd2bb311a4fafd38515cfa71ec to stable v5.14.

`modprobe -r e1000e` triggers a null pointer dereference [1] after the the following two patches are applied to v5.4.y:
d635e7c4b34e6a630c7a1e8f1a8fd52c3e3ceea7 e1000e: Revert "e1000e: Make watchdog use delayed work"
21c6137939723ed6f5e4aec7882cdfc247304c27 e1000e: Drop unnecessary __E1000_DOWN bit twiddling

[1] https://bugs.launchpad.net/bugs/1864303

Kai-Heng

> ---
> 
> RFC v2: Dropped some unused variables
> 	Added logic to check for device present before removing to pm_freeze
> 	Fixed misplaced err_irq to before rtnl_unlock()
> 
> drivers/net/ethernet/intel/e1000e/netdev.c |   40 +++++++++++++++-------------
> 1 file changed, 21 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index d7d56e42a6aa..8b4e589aca36 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -4715,12 +4715,12 @@ int e1000e_close(struct net_device *netdev)
> 
> 	pm_runtime_get_sync(&pdev->dev);
> 
> -	if (!test_bit(__E1000_DOWN, &adapter->state)) {
> +	if (netif_device_present(netdev)) {
> 		e1000e_down(adapter, true);
> 		e1000_free_irq(adapter);
> 
> 		/* Link status message must follow this format */
> -		pr_info("%s NIC Link is Down\n", adapter->netdev->name);
> +		pr_info("%s NIC Link is Down\n", netdev->name);
> 	}
> 
> 	napi_disable(&adapter->napi);
> @@ -6298,10 +6298,14 @@ static int e1000e_pm_freeze(struct device *dev)
> {
> 	struct net_device *netdev = dev_get_drvdata(dev);
> 	struct e1000_adapter *adapter = netdev_priv(netdev);
> +	bool present;
> 
> +	rtnl_lock();
> +
> +	present = netif_device_present(netdev);
> 	netif_device_detach(netdev);
> 
> -	if (netif_running(netdev)) {
> +	if (present && netif_running(netdev)) {
> 		int count = E1000_CHECK_RESET_COUNT;
> 
> 		while (test_bit(__E1000_RESETTING, &adapter->state) && count--)
> @@ -6313,6 +6317,8 @@ static int e1000e_pm_freeze(struct device *dev)
> 		e1000e_down(adapter, false);
> 		e1000_free_irq(adapter);
> 	}
> +	rtnl_unlock();
> +
> 	e1000e_reset_interrupt_capability(adapter);
> 
> 	/* Allow time for pending master requests to run */
> @@ -6626,27 +6632,31 @@ static int __e1000_resume(struct pci_dev *pdev)
> 	return 0;
> }
> 
> -#ifdef CONFIG_PM_SLEEP
> static int e1000e_pm_thaw(struct device *dev)
> {
> 	struct net_device *netdev = dev_get_drvdata(dev);
> 	struct e1000_adapter *adapter = netdev_priv(netdev);
> +	int rc = 0;
> 
> 	e1000e_set_interrupt_capability(adapter);
> -	if (netif_running(netdev)) {
> -		u32 err = e1000_request_irq(adapter);
> 
> -		if (err)
> -			return err;
> +	rtnl_lock();
> +	if (netif_running(netdev)) {
> +		rc = e1000_request_irq(adapter);
> +		if (rc)
> +			goto err_irq;
> 
> 		e1000e_up(adapter);
> 	}
> 
> 	netif_device_attach(netdev);
> +err_irq:
> +	rtnl_unlock();
> 
> -	return 0;
> +	return rc;
> }
> 
> +#ifdef CONFIG_PM_SLEEP
> static int e1000e_pm_suspend(struct device *dev)
> {
> 	struct pci_dev *pdev = to_pci_dev(dev);
> @@ -6818,16 +6828,11 @@ static void e1000_netpoll(struct net_device *netdev)
> static pci_ers_result_t e1000_io_error_detected(struct pci_dev *pdev,
> 						pci_channel_state_t state)
> {
> -	struct net_device *netdev = pci_get_drvdata(pdev);
> -	struct e1000_adapter *adapter = netdev_priv(netdev);
> -
> -	netif_device_detach(netdev);
> +	e1000e_pm_freeze(&pdev->dev);
> 
> 	if (state == pci_channel_io_perm_failure)
> 		return PCI_ERS_RESULT_DISCONNECT;
> 
> -	if (netif_running(netdev))
> -		e1000e_down(adapter, true);
> 	pci_disable_device(pdev);
> 
> 	/* Request a slot slot reset. */
> @@ -6893,10 +6898,7 @@ static void e1000_io_resume(struct pci_dev *pdev)
> 
> 	e1000_init_manageability_pt(adapter);
> 
> -	if (netif_running(netdev))
> -		e1000e_up(adapter);
> -
> -	netif_device_attach(netdev);
> +	e1000e_pm_thaw(&pdev->dev);
> 
> 	/* If the controller has AMT, do not set DRV_LOAD until the interface
> 	 * is up.  For all other cases, let the f/w know that the h/w is now
>