netdev - [PATCH V1 net 2/3] net: ena: fix crash during ena

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Date:   Mon, 19 Nov 2018 12:05:21 +0200
From:   <akiyano@...zon.com>
To:     <davem@...emloft.net>, <netdev@...r.kernel.org>
CC:     Arthur Kiyanovski <akiyano@...zon.com>, <dwmw@...zon.com>,
        <zorik@...zon.com>, <matua@...zon.com>, <saeedb@...zon.com>,
        <msw@...zon.com>, <aliguori@...zon.com>, <nafea@...zon.com>,
        <gtzalik@...zon.com>, <netanel@...zon.com>, <alisaidi@...zon.com>
Subject: [PATCH V1 net 2/3] net: ena: fix crash during ena_remove()

From: Arthur Kiyanovski <akiyano@...zon.com>

In ena_remove() we have the following stack call:
ena_remove()
  unregister_netdev()
  ena_destroy_device()
    netif_carrier_off()

Calling netif_carrier_off() causes linkwatch to try to handle the
link change event on the already unregistered netdev, which leads
to a read from an unreadable memory address.

This patch switches the order of the two functions, so that
netif_carrier_off() is called on a regiestered netdev.

To accomplish this fix we also had to:
1. Remove the set bit ENA_FLAG_TRIGGER_RESET
2. Add a sanitiy check in ena_close()
both to prevent double device reset (when calling unregister_netdev()
ena_close is called, but the device was already deleted in
ena_destroy_device()).
3. Set the admin_queue running state to false to avoid using it after
device was reset (for example when calling ena_destroy_all_io_queues()
right after ena_com_dev_reset() in ena_down)

Fixes: 944b28aa2982 ("net: ena: fix missing lock during device destruction")
Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 1d3cead..a70bb1b 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -1848,6 +1848,8 @@ static void ena_down(struct ena_adapter *adapter)
 		rc = ena_com_dev_reset(adapter->ena_dev, adapter->reset_reason);
 		if (rc)
 			dev_err(&adapter->pdev->dev, "Device reset failed\n");
+		/* stop submitting admin commands on a device that was reset */
+		ena_com_set_admin_running_state(adapter->ena_dev, false);
 	}
 
 	ena_destroy_all_io_queues(adapter);
@@ -1914,6 +1916,9 @@ static int ena_close(struct net_device *netdev)
 
 	netif_dbg(adapter, ifdown, netdev, "%s\n", __func__);
 
+	if (!test_bit(ENA_FLAG_DEVICE_RUNNING, &adapter->flags))
+		return 0;
+
 	if (test_bit(ENA_FLAG_DEV_UP, &adapter->flags))
 		ena_down(adapter);
 
@@ -2613,9 +2618,7 @@ static void ena_destroy_device(struct ena_adapter *adapter, bool graceful)
 		ena_down(adapter);
 
 	/* Stop the device from sending AENQ events (in case reset flag is set
-	 *  and device is up, ena_close already reset the device
-	 * In case the reset flag is set and the device is up, ena_down()
-	 * already perform the reset, so it can be skipped.
+	 *  and device is up, ena_down() already reset the device.
 	 */
 	if (!(test_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags) && dev_up))
 		ena_com_dev_reset(adapter->ena_dev, adapter->reset_reason);
@@ -3452,6 +3455,8 @@ static int ena_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	ena_com_rss_destroy(ena_dev);
 err_free_msix:
 	ena_com_dev_reset(ena_dev, ENA_REGS_RESET_INIT_ERR);
+	/* stop submitting admin commands on a device that was reset */
+	ena_com_set_admin_running_state(ena_dev, false);
 	ena_free_mgmnt_irq(adapter);
 	ena_disable_msix(adapter);
 err_worker_destroy:
@@ -3498,18 +3503,12 @@ static void ena_remove(struct pci_dev *pdev)
 
 	cancel_work_sync(&adapter->reset_task);
 
-	unregister_netdev(netdev);
-
-	/* If the device is running then we want to make sure the device will be
-	 * reset to make sure no more events will be issued by the device.
-	 */
-	if (test_bit(ENA_FLAG_DEVICE_RUNNING, &adapter->flags))
-		set_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags);
-
 	rtnl_lock();
 	ena_destroy_device(adapter, true);
 	rtnl_unlock();
 
+	unregister_netdev(netdev);
+
 	free_netdev(netdev);
 
 	ena_com_rss_destroy(ena_dev);
-- 
2.7.4