[PATCH net] net: enetc: fix destroyed phylink dereference during unbind

From: Vladimir Oltean <vladimir.oltean@nxp.com>

The following call path suggests that calling unregister_netdev on an
interface that is up will first bring it down.

enetc_pf_remove
-> unregister_netdev
   -> unregister_netdevice_queue
      -> unregister_netdevice_many
         -> dev_close_many
            -> __dev_close_many
               -> enetc_close
                  -> enetc_stop
                     -> phylink_stop

However, enetc first destroys the phylink instance, then calls
unregister_netdev. This is already dissimilar to the setup (and error
path teardown path) from enetc_pf_probe, but more than that, it is buggy
because it is invalid to call phylink_stop after phylink_destroy.

So let's first unregister the netdev (and let the .ndo_stop events
consume themselves), then destroy the phylink instance, then free the
netdev.

Fixes: 71b77a7a27a3 ("enetc: Migrate to PHYLINK and PCS_LYNX")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 drivers/net/ethernet/freescale/enetc/enetc_pf.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf.c b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
index 3eb5f1375bd4..515c5b29d7aa 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c

@@ -1157,14 +1157,15 @@ static void enetc_pf_remove(struct pci_dev *pdev)
 	struct enetc_ndev_priv *priv;
 
 	priv = netdev_priv(si->ndev);
-	enetc_phylink_destroy(priv);
-	enetc_mdiobus_destroy(pf);
 
 	if (pf->num_vfs)
 		enetc_sriov_configure(pdev, 0);
 
 	unregister_netdev(si->ndev);
 
+	enetc_phylink_destroy(priv);
+	enetc_mdiobus_destroy(pf);
+
 	enetc_free_msix(priv);
 
 	enetc_free_si_resources(priv);

-- 
2.25.1

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Tue, 16 Feb 2021 12:16:28 +0200 you wrote:

From: Vladimir Oltean <vladimir.oltean@nxp.com>

The following call path suggests that calling unregister_netdev on an
interface that is up will first bring it down.

enetc_pf_remove
-> unregister_netdev
   -> unregister_netdevice_queue
      -> unregister_netdevice_many
         -> dev_close_many
            -> __dev_close_many
               -> enetc_close
                  -> enetc_stop
                     -> phylink_stop

[...]

Here is the summary with links:
  - [net] net: enetc: fix destroyed phylink dereference during unbind
    https://git.kernel.org/netdev/net/c/3af409ca278d

You are awesome, thank you!
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