linux-kernel - Re: [PATCH RESEND net] ptp: Ensure info->enable callback is always set

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Message-ID: <Z5IOHVu9L+QpyK4Y@mev-dev.igk.intel.com>
Date: Thu, 23 Jan 2025 10:38:37 +0100
From: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Richard Cochran <richardcochran@...il.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	John Stultz <john.stultz@...aro.org>, Arnd Bergmann <arnd@...db.de>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH RESEND net] ptp: Ensure info->enable callback is always
 set

On Thu, Jan 23, 2025 at 08:22:40AM +0100, Thomas Weißschuh wrote:
> The ioctl and sysfs handlers unconditionally call the ->enable callback.
> Not all drivers implement that callback, leading to NULL dereferences.
> Example of affected drivers: ptp_s390.c, ptp_vclock.c and ptp_mock.c.
> 
> Instead use a dummy callback if no better was specified by the driver.
> 
> Fixes: d94ba80ebbea ("ptp: Added a brand new class driver for ptp clocks.")
> Cc: stable@...r.kernel.org
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  drivers/ptp/ptp_clock.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index b932425ddc6a3789504164a69d1b8eba47da462c..35a5994bf64f6373c08269d63aaeac3f4ab31ff0 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -217,6 +217,11 @@ static int ptp_getcycles64(struct ptp_clock_info *info, struct timespec64 *ts)
>  		return info->gettime64(info, ts);
>  }
>  
> +static int ptp_enable(struct ptp_clock_info *ptp, struct ptp_clock_request *request, int on)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  static void ptp_aux_kworker(struct kthread_work *work)
>  {
>  	struct ptp_clock *ptp = container_of(work, struct ptp_clock,
> @@ -294,6 +299,9 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
>  			ptp->info->getcrosscycles = ptp->info->getcrosststamp;
>  	}
>  
> +	if (!ptp->info->enable)
> +		ptp->info->enable = ptp_enable;
> +
>  	if (ptp->info->do_aux_work) {
>  		kthread_init_delayed_work(&ptp->aux_work, ptp_aux_kworker);
>  		ptp->kworker = kthread_run_worker(0, "ptp%d", ptp->index);
> 
> ---
> base-commit: c4b9570cfb63501638db720f3bee9f6dfd044b82
> change-id: 20250122-ptp-enable-831339c62428
> 
> Best regards,
> -- 
> Thomas Weißschuh <linux@...ssschuh.net>

Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>

What about other ops, did you check it too? Looks like it isn't needed,
but it sometimes hard to follow.

Thanks