[PATCH net-next] net: altera_tse: fix init sequence to avoid races with register_netdev

[PATCH net-next] net: altera_tse: fix init sequence to avoid races with register_netdev

[Maxime Chevallier]

As reported here[1], the init sequence in altera_tse can be racy should
any operation on the registered netdev happen after netdev registration
but before phylink initialization.

Fix the registering order to avoid such races by making register_netdev
the last step of the probing sequence.

[1]: https://lore.kernel.org/netdev/ZH9XK5yEGyoDMIs%2F@shell.armlinux.org.uk/

Fixes: fef2998203e1 ("net: altera: tse: convert to phylink")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
This patch targets net-next as it fixes a commit that is in net-next
too.

 drivers/net/ethernet/altera/altera_tse_main.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/altera/altera_tse_main.c b/drivers/net/ethernet/altera/altera_tse_main.c
index 2e15800e5310..54f1b5ad84ce 100644
--- a/drivers/net/ethernet/altera/altera_tse_main.c
+++ b/drivers/net/ethernet/altera/altera_tse_main.c
@@ -1395,12 +1395,6 @@ static int altera_tse_probe(struct platform_device *pdev)
 	spin_lock_init(&priv->rxdma_irq_lock);
 
 	netif_carrier_off(ndev);
-	ret = register_netdev(ndev);
-	if (ret) {
-		dev_err(&pdev->dev, "failed to register TSE net device\n");
-		goto err_register_netdev;
-	}
-
 	platform_set_drvdata(pdev, ndev);
 
 	priv->revision = ioread32(&priv->mac_dev->megacore_revision);
@@ -1449,12 +1443,16 @@ static int altera_tse_probe(struct platform_device *pdev)
 		goto err_init_phylink;
 	}
 
+	ret = register_netdev(ndev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register TSE net device\n");
+		return ret;
+	}
+
 	return 0;
 err_init_phylink:
 	lynx_pcs_destroy(priv->pcs);
 err_init_pcs:
-	unregister_netdev(ndev);
-err_register_netdev:
 	netif_napi_del(&priv->napi);
 	altera_tse_mdio_destroy(ndev);
 err_free_netdev:
-- 
2.40.1

Re: [PATCH net-next] net: altera_tse: fix init sequence to avoid races with register_netdev

[Russell King (Oracle)]

On Sun, Jun 11, 2023 at 12:40:19PM +0200, Maxime Chevallier wrote:
> As reported here[1], the init sequence in altera_tse can be racy should
> any operation on the registered netdev happen after netdev registration
> but before phylink initialization.
> 
> Fix the registering order to avoid such races by making register_netdev
> the last step of the probing sequence.
> 
> [1]: https://lore.kernel.org/netdev/ZH9XK5yEGyoDMIs%2F@shell.armlinux.org.uk/
> 
> Fixes: fef2998203e1 ("net: altera: tse: convert to phylink")
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> ---
> This patch targets net-next as it fixes a commit that is in net-next
> too.

While it fixes the order in which stuff is registered, it introduces
a new bug - register_netdev() is what atomically allocated a netdev
name, and you use the netdev name when creating the PCS MII bus:

	snprintf(mrc.name, MII_BUS_ID_SIZE, "%s-pcs-mii", ndev->name);

This needs to change, because this will end up being "eth%d-pcs-mii".

I am at a loss why you didn't realise this (or in fact recognise that
there are other issues) given that I sent you three patches fixing
this mess.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

Re: [PATCH net-next] net: altera_tse: fix init sequence to avoid races with register_netdev

[Maxime Chevallier]

Hi,

On Sun, 11 Jun 2023 16:42:26 +0100
"Russell King (Oracle)" <linux@armlinux.org.uk> wrote:

> On Sun, Jun 11, 2023 at 12:40:19PM +0200, Maxime Chevallier wrote:
> > As reported here[1], the init sequence in altera_tse can be racy should
> > any operation on the registered netdev happen after netdev registration
> > but before phylink initialization.
> > 
> > Fix the registering order to avoid such races by making register_netdev
> > the last step of the probing sequence.
> > 
> > [1]: https://lore.kernel.org/netdev/ZH9XK5yEGyoDMIs%2F@shell.armlinux.org.uk/
> > 
> > Fixes: fef2998203e1 ("net: altera: tse: convert to phylink")
> > Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> > ---
> > This patch targets net-next as it fixes a commit that is in net-next
> > too.  
> 
> While it fixes the order in which stuff is registered, it introduces
> a new bug - register_netdev() is what atomically allocated a netdev
> name, and you use the netdev name when creating the PCS MII bus:
> 
> 	snprintf(mrc.name, MII_BUS_ID_SIZE, "%s-pcs-mii", ndev->name);
> 
> This needs to change, because this will end up being "eth%d-pcs-mii".
> 
> I am at a loss why you didn't realise this (or in fact recognise that
> there are other issues) given that I sent you three patches fixing
> this mess.
> 

Hmpf your patches went un-noticed, sorry... I'll base later work on that.

I will also followup with a similar series for dwmac-socfpga

Best regards,

Maxime