netdev - Re: [PATCH v2 net-next] ptp: Limit time setting of PTP clocks

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Message-ID: <1f56589b-ffd5-4ed2-afb5-18cf2e7692a6@linux.dev>
Date: Thu, 28 Aug 2025 13:53:17 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Miroslav Lichvar <mlichvar@...hat.com>, netdev@...r.kernel.org
Cc: Richard Cochran <richardcochran@...il.com>,
 Thomas Gleixner <tglx@...utronix.de>, John Stultz <jstultz@...gle.com>,
 Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 net-next] ptp: Limit time setting of PTP clocks

On 28/08/2025 11:32, Miroslav Lichvar wrote:
> Networking drivers implementing PTP clocks and kernel socket code
> handling hardware timestamps use the 64-bit signed ktime_t type counting
> nanoseconds. When a PTP clock reaches the maximum value in year 2262,
> the timestamps returned to applications will overflow into year 1667.
> The same thing happens when injecting a large offset with
> clock_adjtime(ADJ_SETOFFSET).
> 
> The commit 7a8e61f84786 ("timekeeping: Force upper bound for setting
> CLOCK_REALTIME") limited the maximum accepted value setting the system
> clock to 30 years before the maximum representable value (i.e. year
> 2232) to avoid the overflow, assuming the system will not run for more
> than 30 years.
> 
> Enforce the same limit for PTP clocks. Don't allow negative values and
> values closer than 30 years to the maximum value. Drivers may implement
> an even lower limit if the hardware registers cannot represent the whole
> interval between years 1970 and 2262 in the required resolution.
> 
> Signed-off-by: Miroslav Lichvar <mlichvar@...hat.com>
> Cc: Richard Cochran <richardcochran@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: John Stultz <jstultz@...gle.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> ---
> 
> Notes:
>      v2:
>      - leave tv_nsec validation separate (Jakub)
> 
>   drivers/ptp/ptp_clock.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index 1cc06b7cb17e..3e0726c6f55b 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -100,6 +100,9 @@ static int ptp_clock_settime(struct posix_clock *pc, const struct timespec64 *tp
>   		return -EBUSY;
>   	}
>   
> +	if (!timespec64_valid_settod(tp))
> +		return -EINVAL;
> +
>   	return  ptp->info->settime64(ptp->info, tp);
>   }
>   
> @@ -130,7 +133,7 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx)
>   	ops = ptp->info;
>   
>   	if (tx->modes & ADJ_SETOFFSET) {
> -		struct timespec64 ts;
> +		struct timespec64 ts, ts2;
>   		ktime_t kt;
>   		s64 delta;
>   
> @@ -143,6 +146,14 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx)
>   		if ((unsigned long) ts.tv_nsec >= NSEC_PER_SEC)
>   			return -EINVAL;
>   
> +		/* Make sure the offset is valid */
> +		err = ptp_clock_gettime(pc, &ts2);
> +		if (err)
> +			return err;
> +		ts2 = timespec64_add(ts2, ts);
> +		if (!timespec64_valid_settod(&ts2))
> +			return -EINVAL;
> +
>   		kt = timespec64_to_ktime(ts);
>   		delta = ktime_to_ns(kt);
>   		err = ops->adjtime(ops, delta);

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@...ux.dev>