netdev - Re: [PATCH] posix-clock: Explicitly handle compat ioctls

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Message-ID: <20250122095204.GB385045@kernel.org>
Date: Wed, 22 Jan 2025 09:52:04 +0000
From: Simon Horman <horms@...nel.org>
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>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <johnstul@...ibm.com>, Arnd Bergmann <arnd@...db.de>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Cyrill Gorcunov <gorcunov@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH] posix-clock: Explicitly handle compat ioctls

On Tue, Jan 21, 2025 at 11:41:24PM +0100, Thomas Weißschuh wrote:
> Pointer arguments passed to ioctls need to pass through compat_ptr() to
> work correctly on s390; as explained in Documentation/driver-api/ioctl.rst.
> Plumb the compat_ioctl callback through 'struct posix_clock_operations'
> and handle the different ioctls cmds in the new ptp_compat_ioctl().
> 
> Using compat_ptr_ioctl is not possible.
> For the commands PTP_ENABLE_PPS/PTP_ENABLE_PPS2 on s390
> it would corrupt the argument 0x80000000, aka BIT(31) to zero.
> 
> Fixes: 0606f422b453 ("posix clocks: Introduce dynamic clocks")
> 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>

...

> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index 77a36e7bddd54e8f45eab317e687f033f57cc5bc..dec84b81cedfd13bcf8c97be6c3c27d73cd671f6 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -180,6 +180,7 @@ static struct posix_clock_operations ptp_clock_ops = {
>  	.clock_getres	= ptp_clock_getres,
>  	.clock_settime	= ptp_clock_settime,
>  	.ioctl		= ptp_ioctl,
> +	.compat_ioctl	= ptp_compat_ioctl,
>  	.open		= ptp_open,
>  	.release	= ptp_release,
>  	.poll		= ptp_poll,


nit: compat_ioctl should also be added to the Kernel doc for
     struct posix_clock_operations

...