by Simon Horman

[permalink] [raw]

Subject: Re: [PATCH net-next v12 12/13] net: ethtool: tsinfo: Add support for hwtstamp provider and get/set hwtstamp config

On Tue, Apr 30, 2024 at 05:49:55PM +0200, Kory Maincent wrote:
> Enhance 'get' command to retrieve tsinfo of hwtstamp providers within a
> network topology and read current hwtstamp configuration.
>
> Introduce support for ETHTOOL_MSG_TSINFO_SET ethtool netlink socket to
> configure hwtstamp of a PHC provider. Note that simultaneous hwtstamp
> isn't supported; configuring a new one disables the previous setting.
>
> Also, add support for a specific dump command to retrieve all hwtstamp
> providers within the network topology, with added functionality for
> filtered dump to target a single interface.
>
> Signed-off-by: Kory Maincent <[email protected]>

..

> diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
> index acb0cadb7512..ec6dd81a5add 100644
> --- a/net/core/dev_ioctl.c
> +++ b/net/core/dev_ioctl.c
> @@ -270,10 +270,13 @@ static int dev_eth_ioctl(struct net_device *dev,
> int dev_get_hwtstamp_phylib(struct net_device *dev,
> struct kernel_hwtstamp_config *cfg)
> {
> - if (dev->hwtstamp) {
> - struct ptp_clock *ptp = dev->hwtstamp->ptp;
> + struct hwtstamp_provider *hwtstamp;
>
> - cfg->qualifier = dev->hwtstamp->qualifier;
> + hwtstamp = rtnl_dereference(dev->hwtstamp);
> + if (hwtstamp) {
> + struct ptp_clock *ptp = hwtstamp->ptp;
> +
> + cfg->qualifier = hwtstamp->qualifier;
> if (ptp_clock_from_phylib(ptp))
> return phy_hwtstamp_get(ptp_clock_phydev(ptp), cfg);
>
> @@ -340,13 +343,15 @@ int dev_set_hwtstamp_phylib(struct net_device *dev,
> {
> const struct net_device_ops *ops = dev->netdev_ops;
> struct kernel_hwtstamp_config old_cfg = {};
> + struct hwtstamp_provider *hwtstamp;
> struct phy_device *phydev;
> bool changed = false;
> bool phy_ts;
> int err;
>
> - if (dev->hwtstamp) {
> - struct ptp_clock *ptp = dev->hwtstamp->ptp;
> + hwtstamp = rtnl_dereference(dev->hwtstamp);
> + if (hwtstamp) {
> + struct ptp_clock *ptp = hwtstamp->ptp;
>
> if (ptp_clock_from_phylib(ptp)) {
> phy_ts = true;

Hi Kory,

A few lines beyond this hunk, within the "if (hwtstamp)" block,
is the following:

cfg->qualifier = dev->hwtstamp->qualifier;

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:

cfg->qualifier = hwtstamp->qualifier;

Flagged by Sparse.

..

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

..

> +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 = (void *)cb->ctx;
> + struct ptp_clock *ptp;
> + int ret;
> +
> + netdev_for_each_ptp_clock_start(dev, ctx->pos_phcindex, ptp,
> + ctx->pos_phcindex) {
> + ret = ethnl_tsinfo_dump_one_ptp(skb, dev, cb, ptp);
> + if (ret < 0 && ret != -EOPNOTSUPP)
> + break;
> + ctx->pos_phcqualifier = HWTSTAMP_PROVIDER_QUALIFIER_PRECISE;
> + }
> +
> + return ret;

Perhaps it is not possible, but if the loop iterates zero times then
ret will be used uninitialised here.

Flagged by Smatch.

> +}

..

2024-05-17 15:21:37

by Kory Maincent

[permalink] [raw]

Subject: Re: [PATCH net-next v12 12/13] net: ethtool: tsinfo: Add support for hwtstamp provider and get/set hwtstamp config

On Sat, 4 May 2024 11:33:05 +0100
Simon Horman <[email protected]> wrote:

> Hi Kory,
>
> A few lines beyond this hunk, within the "if (hwtstamp)" block,
> is the following:
>
> cfg->qualifier = dev->hwtstamp->qualifier;
>
> 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:
>
> cfg->qualifier = hwtstamp->qualifier;
>
> Flagged by Sparse.

Yes indeed, thanks for the report.

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

Yes thanks!

Regards,
--
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com