linux-kernel - Re: [PATCH net] net: phy: mscc: Fix memory leak when using one step timestamping

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Message-ID: <20250522114926.oavrusoaqnj6e77q@DEN-DL-M31836.microchip.com>
Date: Thu, 22 May 2025 13:49:26 +0200
From: Horatiu Vultur <horatiu.vultur@...rochip.com>
To: Antoine Tenart <atenart@...nel.org>
CC: <andrew@...n.ch>, <hkallweit1@...il.com>, <linux@...linux.org.uk>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <richardcochran@...il.com>, <kory.maincent@...tlin.com>,
	<shannon.nelson@....com>, <viro@...iv.linux.org.uk>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: phy: mscc: Fix memory leak when using one step
 timestamping

The 05/21/2025 17:34, Antoine Tenart wrote:

Hi Antoine,

> 
> On Wed, May 21, 2025 at 03:11:14PM +0200, Horatiu Vultur wrote:
> > Fix memory leak when running one-step timestamping. When running
> > one-step sync timestamping, the HW is configured to insert the TX time
> > into the frame, so there is no reason to keep the skb anymore. As in
> > this case the HW will never generate an interrupt to say that the frame
> > was timestamped, then the frame will never released.
> > Fix this by freeing the frame in case of one-step timestamping.
> >
> > Fixes: 7d272e63e0979d ("net: phy: mscc: timestamping and PHC support")
> > Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
> > ---
> >  drivers/net/phy/mscc/mscc_ptp.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/net/phy/mscc/mscc_ptp.c b/drivers/net/phy/mscc/mscc_ptp.c
> > index ed8fb14a7f215..db8ca1dfd5322 100644
> > --- a/drivers/net/phy/mscc/mscc_ptp.c
> > +++ b/drivers/net/phy/mscc/mscc_ptp.c
> > @@ -1173,6 +1173,13 @@ static void vsc85xx_txtstamp(struct mii_timestamper *mii_ts,
> >               return;
> >       }
> >
> > +     if (vsc8531->ptp->tx_type == HWTSTAMP_TX_ONESTEP_SYNC) {
> > +             if (ptp_msg_is_sync(skb, type)) {
> > +                     kfree_skb(skb);
> > +                     return;
> > +             }
> > +     }
> 
> I don't remember everything about TS but I think the above is fine. Also
> while looking at this I saw this function is doing the following too:
> 
>   if (!vsc8531->ptp->configured)
>         return;
> 
> I guess we should free the skb for all paths not putting it in the tx
> queue. As there would be 3 paths freeing the skb + returning, you might
> as well use a label for easier maintenance.

Yes, you are correct we should free the skb also in this case.
I will fix this in the next version.

> 
> Thanks,
> Antoine

-- 
/Horatiu