[PATCH net] iavf: Detach device during reset task

[Ivan Vecera <ivecera@redhat.com>]

iavf_reset_task() takes crit_lock at the beginning and holds
it during whole call. The function subsequently calls
iavf_init_interrupt_scheme() that grabs RTNL. Problem occurs
when userspace initiates during the reset task any ndo callback
that runs under RTNL like iavf_open() because some of that
functions tries to take crit_lock. This leads to classic A-B B-A
deadlock scenario.

To resolve this situation the device should be detached in
iavf_reset_task() prior taking crit_lock to avoid subsequent
ndos running under RTNL and reattach the device at the end.

Fixes: 62fe2a865e6d ("i40evf: add missing rtnl_lock() around i40evf_set_interrupt_capability")
Cc: Jacob Keller <jacob.e.keller@intel.com>
Cc: Patryk Piotrowski <patryk.piotrowski@intel.com>
Tested-by: Vitaly Grinberg <vgrinber@redhat.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
 drivers/net/ethernet/intel/iavf/iavf_main.c | 22 +++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c b/drivers/net/ethernet/intel/iavf/iavf_main.c
index f39440ad5c50..ee8f911b57ea 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_main.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
@@ -2877,6 +2877,13 @@ static void iavf_reset_task(struct work_struct *work)
 	int i = 0, err;
 	bool running;
 
+	/*
+	 * Detach interface to avoid subsequent NDO callbacks
+	 */
+	rtnl_lock();
+	netif_device_detach(netdev);
+	rtnl_unlock();
+
 	/* When device is being removed it doesn't make sense to run the reset
 	 * task, just return in such a case.
 	 */
@@ -2884,7 +2891,7 @@ static void iavf_reset_task(struct work_struct *work)
 		if (adapter->state != __IAVF_REMOVE)
 			queue_work(iavf_wq, &adapter->reset_task);
 
-		return;
+		goto reset_finish;
 	}
 
 	while (!mutex_trylock(&adapter->client_lock))
@@ -2954,7 +2961,6 @@ static void iavf_reset_task(struct work_struct *work)
 
 	if (running) {
 		netif_carrier_off(netdev);
-		netif_tx_stop_all_queues(netdev);
 		adapter->link_up = false;
 		iavf_napi_disable_all(adapter);
 	}
@@ -3081,10 +3087,8 @@ static void iavf_reset_task(struct work_struct *work)
 
 	adapter->flags &= ~IAVF_FLAG_REINIT_ITR_NEEDED;
 
-	mutex_unlock(&adapter->client_lock);
-	mutex_unlock(&adapter->crit_lock);
+	goto reset_finish;
 
-	return;
 reset_err:
 	if (running) {
 		set_bit(__IAVF_VSI_DOWN, adapter->vsi.state);
@@ -3092,9 +3096,15 @@ static void iavf_reset_task(struct work_struct *work)
 	}
 	iavf_disable_vf(adapter);
 
+	dev_err(&adapter->pdev->dev, "failed to allocate resources during reinit\n");
+
+reset_finish:
 	mutex_unlock(&adapter->client_lock);
 	mutex_unlock(&adapter->crit_lock);
-	dev_err(&adapter->pdev->dev, "failed to allocate resources during reinit\n");
+
+	rtnl_lock();
+	netif_device_attach(netdev);
+	rtnl_unlock();
 }
 
 /**
-- 
2.35.1