linux-kernel - Re: [PATCH net 1/1] net: dsa: sja1105: fix error handling on NULL returned by xpcs

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Date:   Tue, 10 Aug 2021 08:25:29 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Wong Vee Khee <vee.khee.wong@...ux.intel.com>
CC:     Vladimir Oltean <olteanv@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net 1/1] net: dsa: sja1105: fix error handling on NULL
 returned by xpcs_create()

Hi VK,

On Tue, Aug 10, 2021 at 02:35:13PM +0800, Wong Vee Khee wrote:
> There is a possibility xpcs_create() returned a NULL and this is not
> handled properly in the sja1105 driver.
> 
> Fixed this by using IS_ERR_ON_NULL() instead of IS_ERR().
> 
> Fixes: 3ad1d171548e ("net: dsa: sja1105: migrate to xpcs for SGMII")
> Cc: Vladimir Olten <vladimir.oltean@....com>
> Signed-off-by: Wong Vee Khee <vee.khee.wong@...ux.intel.com>
> ---
>  drivers/net/dsa/sja1105/sja1105_mdio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/sja1105/sja1105_mdio.c b/drivers/net/dsa/sja1105/sja1105_mdio.c
> index 19aea8fb76f6..2c69a759ce6e 100644
> --- a/drivers/net/dsa/sja1105/sja1105_mdio.c
> +++ b/drivers/net/dsa/sja1105/sja1105_mdio.c
> @@ -438,7 +438,7 @@ static int sja1105_mdiobus_pcs_register(struct sja1105_private *priv)
>  		}
>  
>  		xpcs = xpcs_create(mdiodev, priv->phy_mode[port]);
> -		if (IS_ERR(xpcs)) {
> +		if (IS_ERR_OR_NULL(xpcs)) {
>  			rc = PTR_ERR(xpcs);
>  			goto out_pcs_free;
>  		}
> -- 
> 2.25.1
> 

I think posting to 'net' is a bit drastic for this patch. I agree it is
an issue but it has bothered absolutely nobody so far, and if sending
this patch to 'net' means you'll be blocked with your patches until the
'net'->'net-next' merge, I'm not sure it's worth it.

Anyway, I don't think that PTR_ERR(xpcs) does the right thing when
IS_NULL(xpcs). So how about you make this change:

-----------------------------[ cut here ]-----------------------------
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
index a5d150c5f3d8..ca12bf986d4d 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -415,7 +415,7 @@ int stmmac_xpcs_setup(struct mii_bus *bus)
 			continue;
 
 		xpcs = xpcs_create(mdiodev, mode);
-		if (IS_ERR_OR_NULL(xpcs)) {
+		if (IS_ERR(xpcs)) {
 			mdio_device_free(mdiodev);
 			continue;
 		}
diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index 63fda3fc40aa..4bd61339823c 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -1089,7 +1089,7 @@ struct dw_xpcs *xpcs_create(struct mdio_device *mdiodev,
 
 	xpcs = kzalloc(sizeof(*xpcs), GFP_KERNEL);
 	if (!xpcs)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	xpcs->mdiodev = mdiodev;
 
-----------------------------[ cut here ]-----------------------------