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Date: Fri, 17 May 2024 17:12:54 +0200
From: Kory Maincent <kory.maincent@bootlin.com>
To: Simon Horman <horms@kernel.org>
Cc: Florian Fainelli <florian.fainelli@broadcom.com>, Broadcom internal
 kernel review list <bcm-kernel-feedback-list@broadcom.com>, Andrew Lunn
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Subject: Re: [PATCH net-next v12 12/13] net: ethtool: tsinfo: Add support
 for hwtstamp provider and get/set hwtstamp config
Message-ID: <20240517171254.1e316e69@kmaincent-XPS-13-7390>
In-Reply-To: <20240504103305.GD3167983@kernel.org>
References: <20240430-feature_ptp_netnext-v12-0-2c5f24b6a914@bootlin.com>
	<20240430-feature_ptp_netnext-v12-12-2c5f24b6a914@bootlin.com>
	<20240504103305.GD3167983@kernel.org>
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On Sat, 4 May 2024 11:33:05 +0100
Simon Horman <horms@kernel.org> wrote:

> Hi Kory,
>=20
> A few lines beyond this hunk, within the "if (hwtstamp)" block,
> is the following:
>=20
> 		cfg->qualifier =3D dev->hwtstamp->qualifier;
>=20
> Now that dev->hwtstamp is managed using RCU, I don't think it is correct
> to dereference it directly like this. Rather, the hwtstamp local variable,
> which has rcu_dereference'd this pointer should be used:
>=20
> 		 cfg->qualifier =3D hwtstamp->qualifier;
>=20
> Flagged by Sparse.

Yes indeed, thanks for the report.

>=20
> ...
>=20
> > diff --git a/net/ethtool/tsinfo.c b/net/ethtool/tsinfo.c =20
>=20
> ...
>=20
> > +static int ethnl_tsinfo_dump_one_dev(struct sk_buff *skb, struct
> > net_device *dev,
> > +				     struct netlink_callback *cb)
> > +{
> > +	struct ethnl_tsinfo_dump_ctx *ctx =3D (void *)cb->ctx;
> > +	struct ptp_clock *ptp;
> > +	int ret;
> > +
> > +	netdev_for_each_ptp_clock_start(dev, ctx->pos_phcindex, ptp,
> > +					ctx->pos_phcindex) {
> > +		ret =3D ethnl_tsinfo_dump_one_ptp(skb, dev, cb, ptp);
> > +		if (ret < 0 && ret !=3D -EOPNOTSUPP)
> > +			break;
> > +		ctx->pos_phcqualifier =3D
> > HWTSTAMP_PROVIDER_QUALIFIER_PRECISE;
> > +	}
> > +
> > +	return ret; =20
>=20
> Perhaps it is not possible, but if the loop iterates zero times then
> ret will be used uninitialised here.

Yes thanks!

Regards,
--=20
K=C3=B6ry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com