Re: [PATCH net-next v4 07/13] net: ethtool: Introduce a command to list PHYs on an interface

From: Simon Horman <horms@kernel.org>
To: Maxime Chevallier <maxime.chevallier@bootlin.com>
Cc: davem@davemloft.net, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Eric Dumazet" <edumazet@google.com>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Russell King" <linux@armlinux.org.uk>,
	linux-arm-kernel@lists.infradead.org,
	"Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Herve Codina" <herve.codina@bootlin.com>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Heiner Kallweit" <hkallweit1@gmail.com>,
	"Vladimir Oltean" <vladimir.oltean@nxp.com>,
	"Köry Maincent" <kory.maincent@bootlin.com>,
	"Jesse Brandeburg" <jesse.brandeburg@intel.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Marek Behún" <kabel@kernel.org>,
	"Piergiorgio Beruto" <piergiorgio.beruto@gmail.com>,
	"Oleksij Rempel" <o.rempel@pengutronix.de>,
	"Nicolò Veronese" <nicveronese@gmail.com>
Subject: Re: [PATCH net-next v4 07/13] net: ethtool: Introduce a command to list PHYs on an interface
Date: Tue, 19 Dec 2023 08:55:57 +0000	[thread overview]
Message-ID: <20231219085557.GB811967@kernel.org> (raw)
In-Reply-To: <20231215171237.1152563-8-maxime.chevallier@bootlin.com>

On Fri, Dec 15, 2023 at 06:12:29PM +0100, Maxime Chevallier wrote:
> As we have the ability to track the PHYs connected to a net_device
> through the link_topology, we can expose this list to userspace. This
> allows userspace to use these identifiers for phy-specific commands and
> take the decision of which PHY to target by knowing the link topology.
> 
> Add PHY_GET and PHY_DUMP, which can be a filtered DUMP operation to list
> devices on only one interface.
> 
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Hi Maxime,

some minor feedback from my side.

> +static int ethnl_phy_parse_request(struct ethnl_req_info *req_base,
> +				   struct nlattr **tb)
> +{
> +	struct phy_req_info *req_info = PHY_REQINFO(req_base);
> +	struct phy_link_topology *topo = &req_base->dev->link_topo;
> +	struct phy_device_node *pdn;

nit: Please consider arranging local variables in reverse xmas tree order -
     longest line to shortest.

> +
> +	if (!req_base->phydev)
> +		return 0;
> +
> +	pdn = xa_load(&topo->phys, req_base->phydev->phyindex);
> +	memcpy(&req_info->pdn, pdn, sizeof(*pdn));
> +
> +	return 0;
> +}

...

> +static int ethnl_phy_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
> +				  struct netlink_callback *cb)
> +{
> +	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
> +	struct phy_req_info *pri = ctx->phy_req_info;
> +	struct phy_device_node *pdn;
> +	unsigned long index = 1;
> +	void *ehdr;
> +	int ret;
> +
> +	pri->base.dev = dev;
> +
> +	xa_for_each(&dev->link_topo.phys, index, pdn) {
> +		ehdr = ethnl_dump_put(skb, cb,
> +				      ETHTOOL_MSG_PHY_GET_REPLY);
> +		if (!ehdr) {
> +			ret = -EMSGSIZE;
> +			break;
> +		}
> +
> +		ret = ethnl_fill_reply_header(skb, dev,
> +					      ETHTOOL_A_PHY_HEADER);
> +		if (ret < 0) {
> +			genlmsg_cancel(skb, ehdr);
> +			break;
> +		}
> +
> +		memcpy(&pri->pdn, pdn, sizeof(*pdn));
> +		ret = ethnl_phy_fill_reply(&pri->base, skb);
> +
> +		genlmsg_end(skb, ehdr);
> +	}
> +
> +	return ret;

I'm unsure if it can happen, but if the loop runs zero times then
ret will be used uninitialised here.

Flagged by Smatch.

> +}

...

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