Re: [PATCH 0/3] Modernize tasklet callback API

From: Kees Cook <keescook@chromium.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kuppuswamy Sathyanarayanan
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Oscar Carter <oscar.carter@gmx.com>,
	Mitchell Blank Jr <mitch@sfgoth.com>,
	kernel-hardening@lists.openwall.com,
	kgdb-bugreport@lists.sourceforge.net,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	alsa-devel@alsa-project.org, Allen Pais <allen.lkml@gmail.com>,
	netdev@vger.kernel.org,
	Christian Gromm <christian.gromm@microchip.com>,
	Will Deacon <will@kernel.org>,
	devel@driverdev.osuosl.org, Jonathan Corbet <corbet@lwn.net>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	"David S. Miller" <davem@davemloft.net>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Takashi Iwai <tiwai@suse.com>,
	Julian Wiedmann <jwi@linux.ibm.com>,
	"Matthew Wilcox \(Oracle\)" <willy@infradead.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Nishka Dasgupta <nishkadg.linux@gmail.com>,
	Jiri Slaby <jslaby@suse.com>, Jakub Kicinski <kuba@kernel.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Wambui Karuga <wambui.karugax@gmail.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	Heiko Carstens <hca@linux.ibm.com>,
	linux-input@vger.kernel.org, Ursula Braun <ubraun@linux.ibm.com>,
	Stephen Boyd <swboyd@chromium.org>,
	Chris Packham <chris.packham@alliedtelesis.co.nz>,
	Harald Freudenberger <freude@linux.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jaroslav Kysela <perex@perex.cz>, Felipe Balbi <balbi@kernel.org>,
	Kyungtae Kim <kt0755@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Douglas Anderson <dianders@chromium.org>,
	Kevin Curtis <kevin.curtis@farsite.co.uk>,
	linux-usb@vger.kernel.org,
	Jason Wessel <jason.wessel@windriver.com>,
	Romain Perier <romain.perier@gmail.com>,
	Karsten Graul <kgraul@linux.ibm.com>
Subject: Re: [PATCH 0/3] Modernize tasklet callback API
Date: Thu, 16 Jul 2020 12:14:46 -0700	[thread overview]
Message-ID: <202007161214.102F6E6@keescook> (raw)
In-Reply-To: <20200716075718.GM10769@hirez.programming.kicks-ass.net>

On Thu, Jul 16, 2020 at 09:57:18AM +0200, Peter Zijlstra wrote:
> On Wed, Jul 15, 2020 at 08:08:44PM -0700, Kees Cook wrote:
> > Hi,
> > 
> > This is the infrastructure changes to prepare the tasklet API for
> > conversion to passing the tasklet struct as the callback argument instead
> > of an arbitrary unsigned long. The first patch details why this is useful
> > (it's the same rationale as the timer_struct changes from a bit ago:
> > less abuse during memory corruption attacks, more in line with existing
> > ways of doing things in the kernel, save a little space in struct,
> > etc). Notably, the existing tasklet API use is much less messy, so there
> > is less to clean up.
> 
> I would _MUCH_ rather see tasklets go the way of the dodo, esp. given
> that:
> 
> >  drivers/input/keyboard/omap-keypad.c   |  2 +-
> >  drivers/input/serio/hil_mlc.c          |  2 +-
> >  drivers/net/wan/farsync.c              |  4 +--
> >  drivers/s390/crypto/ap_bus.c           |  2 +-
> >  drivers/staging/most/dim2/dim2.c       |  2 +-
> >  drivers/staging/octeon/ethernet-tx.c   |  2 +-
> >  drivers/tty/vt/keyboard.c              |  2 +-
> >  drivers/usb/gadget/udc/snps_udc_core.c |  6 ++---
> >  drivers/usb/host/fhci-sched.c          |  2 +-
> >  include/linux/interrupt.h              | 37 ++++++++++++++++++++++----
> >  kernel/backtracetest.c                 |  2 +-
> >  kernel/debug/debug_core.c              |  2 +-
> >  kernel/irq/resend.c                    |  2 +-
> >  kernel/softirq.c                       | 18 ++++++++++++-
> >  net/atm/pppoatm.c                      |  2 +-
> >  net/iucv/iucv.c                        |  2 +-
> >  sound/drivers/pcsp/pcsp_lib.c          |  2 +-
> >  17 files changed, 66 insertions(+), 25 deletions(-)
> 
> there appear to be hardly any users left.. Can't we stage an extinction
> event here instead?

Oh, I wish, but no. That's just the ones using DECLARE_TASKLET. There
are hundred(s?) more (see the referenced tree).

-- 
Kees Cook
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