linux-kernel - Re: [RFC PATCH net-next v3 07/13] net: ethtool: Introduce a command to list PHYs on an interface

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Message-ID: <20231209170457.GB5817@kernel.org>
Date:   Sat, 9 Dec 2023 17:04:57 +0000
From:   Simon Horman <horms@...nel.org>
To:     Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
        Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Herve Codina <herve.codina@...tlin.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Köry Maincent <kory.maincent@...tlin.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Marek Behún <kabel@...nel.org>,
        Piergiorgio Beruto <piergiorgio.beruto@...il.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Nicolò Veronese <nicveronese@...il.com>
Subject: Re: [RFC PATCH net-next v3 07/13] net: ethtool: Introduce a command
 to list PHYs on an interface

On Fri, Dec 01, 2023 at 05:36:57PM +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@...tlin.com>

...

> diff --git a/net/ethtool/phy.c b/net/ethtool/phy.c

...

> +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;

Hi Maxime,

I am unsure if this can happen (or if I flagged this before)
but if the loop runs zero times then ret is uninitialised here.

Flagged by Smatch

> +}

...