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

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Message-ID: <Z5Ebh4pbOUGh64BS@hoboy.vegasvil.org>
Date: Wed, 22 Jan 2025 08:23:35 -0800
From: Richard Cochran <richardcochran@...il.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
	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 Gleixner <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <johnstul@...ibm.com>, Netdev <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 Wed, Jan 22, 2025 at 08:30:51AM +0100, Arnd Bergmann wrote:
> On Tue, Jan 21, 2025, at 23:41, 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>
> 
> This looks correct to me,

I'm not familiar with s390, but I can remember that the compat ioctl
was nixed during review.

   https://lore.kernel.org/lkml/201012161716.42520.arnd@arndb.de/

   https://lore.kernel.org/lkml/alpine.LFD.2.00.1012161939340.12146@localhost6.localdomain6/

Can you explain what changed or what was missed?

Thanks,
Richard