linux-kernel - Re: [PATCH net v2] net: phy: mscc: Fix memory leak when using one step timestamping

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Message-ID: <rcdapvt2pt6zntthvvwzualqrhoeaqc4oq2jsyqxjxavvfwabb@k3p5fweby7mb>
Date: Thu, 22 May 2025 14:39:25 +0200
From: Antoine Tenart <atenart@...nel.org>
To: Horatiu Vultur <horatiu.vultur@...rochip.com>
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, 
	rrameshbabu@...dia.com, viro@...iv.linux.org.uk, quentin.schulz@...tlin.com, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] net: phy: mscc: Fix memory leak when using one
 step timestamping

On Thu, May 22, 2025 at 01:57:22PM +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>
> 
> ---
> v1->v2: Free the skb also when ptp is not configured
> ---
>  drivers/net/phy/mscc/mscc_ptp.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/phy/mscc/mscc_ptp.c b/drivers/net/phy/mscc/mscc_ptp.c
> index ed8fb14a7f215..6f96f2679f0bf 100644
> --- a/drivers/net/phy/mscc/mscc_ptp.c
> +++ b/drivers/net/phy/mscc/mscc_ptp.c
> @@ -1166,18 +1166,24 @@ static void vsc85xx_txtstamp(struct mii_timestamper *mii_ts,
>  		container_of(mii_ts, struct vsc8531_private, mii_ts);
>  
>  	if (!vsc8531->ptp->configured)
> -		return;
> +		goto out;
>  
> -	if (vsc8531->ptp->tx_type == HWTSTAMP_TX_OFF) {
> -		kfree_skb(skb);
> -		return;
> -	}
> +	if (vsc8531->ptp->tx_type == HWTSTAMP_TX_OFF)
> +		goto out;
> +
> +	if (vsc8531->ptp->tx_type == HWTSTAMP_TX_ONESTEP_SYNC)
> +		if (ptp_msg_is_sync(skb, type))
> +			goto out;

nit: you can combine the two checks and avoid having nested if
statements.

>  	skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
>  
>  	mutex_lock(&vsc8531->ts_lock);
>  	__skb_queue_tail(&vsc8531->ptp->tx_queue, skb);
>  	mutex_unlock(&vsc8531->ts_lock);
> +	return;
> +
> +out:
> +	kfree_skb(skb);
>  }
>  
>  static bool vsc85xx_rxtstamp(struct mii_timestamper *mii_ts,
> -- 
> 2.34.1
> 
>