[PATCH 1/5] idpf: skip getting/setting ring params if vport is NULL during HW reset

[Li Li <boolli@google.com>]

When an idpf HW reset is triggered, it clears the vport but does
not clear the netdev held by vport:

    // In idpf_vport_dealloc() called by idpf_init_hard_reset(),
    // idpf_init_hard_reset() sets IDPF_HR_RESET_IN_PROG, so
    // idpf_decfg_netdev() doesn't get called.
    if (!test_bit(IDPF_HR_RESET_IN_PROG, adapter->flags))
        idpf_decfg_netdev(vport);
    // idpf_decfg_netdev() would clear netdev but it isn't called:
    unregister_netdev(vport->netdev);
    free_netdev(vport->netdev);
    vport->netdev = NULL;
    // Later in idpf_init_hard_reset(), the vport is cleared:
    kfree(adapter->vports);
    adapter->vports = NULL;

During an idpf HW reset, when "ethtool -g/-G" is called on the netdev,
the vport associated with the netdev is NULL, and so a kernel panic
would happen:

[  513.185327] BUG: kernel NULL pointer dereference, address: 0000000000000038
...
[  513.232756] RIP: 0010:idpf_get_ringparam+0x45/0x80

This can be reproduced reliably by injecting a TX timeout to cause
an idpf HW reset, and injecting a virtchnl error to cause the HW
reset to fail and retry, while calling "ethtool -g/-G" on the netdev
at the same time.

With this patch applied, we see the following error but no kernel
panics anymore:

[  476.323630] idpf 0000:05:00.0 eth1: failed to get ring params due to no vport in netdev

Signed-off-by: Li Li <boolli@google.com>
---
 drivers/net/ethernet/intel/idpf/idpf_ethtool.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_ethtool.c b/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
index d5711be0b8e69..6a4b630b786c2 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_ethtool.c
@@ -639,6 +638,10 @@ static void idpf_get_ringparam(struct net_device *netdev,
 
 	idpf_vport_ctrl_lock(netdev);
 	vport = idpf_netdev_to_vport(netdev);
+	if (!vport) {
+		netdev_err(netdev, "failed to get ring params due to no vport in netdev\n");
+		goto unlock;
+	}
 
 	ring->rx_max_pending = IDPF_MAX_RXQ_DESC;
 	ring->tx_max_pending = IDPF_MAX_TXQ_DESC;
@@ -647,6 +651,7 @@ static void idpf_get_ringparam(struct net_device *netdev,
 
 	kring->tcp_data_split = idpf_vport_get_hsplit(vport);
 
+unlock:
 	idpf_vport_ctrl_unlock(netdev);
 }
 
@@ -673,6 +674,11 @@ static int idpf_set_ringparam(struct net_device *netdev,
 
 	idpf_vport_ctrl_lock(netdev);
 	vport = idpf_netdev_to_vport(netdev);
+	if (!vport) {
+		netdev_err(netdev, "ring params not changed due to no vport in netdev\n");
+		err = -EFAULT;
+		goto unlock_mutex;
+	}
 
 	idx = vport->idx;
 
-- 
2.52.0.351.gbe84eed79e-goog