From: Kent Gibson <warthog618@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH 10/22] gpiolib: cdev: fix minor race in GET_LINEINFO_WATCH
Date: Thu, 25 Jun 2020 17:36:47 +0800 [thread overview]
Message-ID: <20200625093647.GA18209@sol> (raw)
In-Reply-To: <CAHp75VeDOGArs2MxJJRNHbNRsJU4K+KYPY=pF+mgtwbakQf4BQ@mail.gmail.com>
On Thu, Jun 25, 2020 at 12:23:49PM +0300, Andy Shevchenko wrote:
> On Thu, Jun 25, 2020 at 12:13 PM Kent Gibson <warthog618@gmail.com> wrote:
> > On Thu, Jun 25, 2020 at 11:44:21AM +0300, Andy Shevchenko wrote:
> > > On Thu, Jun 25, 2020 at 1:58 AM Kent Gibson <warthog618@gmail.com> wrote:
> > > > On Wed, Jun 24, 2020 at 11:57:14PM +0800, Kent Gibson wrote:
>
> ...
>
> > > > Perhaps you are referring to the case where the copy_to_user fails?
> > >
> > > Yes.
> > >
> > > > To be honest I considered that to be so unlikely that I ignored it.
> > > > Is there a relevant failure mode that I'm missing?
> > >
> > > The traditional question for such cases is "what can possibly go wrong?"
> > > I wouldn't underestimate the probability of failure.
> > >
> >
> > The worst case is the watch is enabled and the userspace gets an
> > EFAULT so it thinks it failed. If userspace retries then they get
> > EBUSY, so userspace accounting gets muddled.
> >
> > We can clear the watch bit if the copy_to_user fails - before
> > returning the EFAULT. Would that be satisfactory?
>
> Perhaps. I didn't check that scenario.
>
To be clear I'm suggesting this:
gpio_desc_to_lineinfo(desc, &lineinfo);
- if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
+ if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) {
+ clear_bit(lineinfo.offset, gcdev->watched_lines);
return -EFAULT;
+ }
That undoes the set, returning the watch state to what it was before the
call.
Cheers,
Kent.
next prev parent reply other threads:[~2020-06-25 9:36 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 4:00 [PATCH 00/22] gpio: cdev: add uAPI V2 Kent Gibson
2020-06-23 4:00 ` [PATCH 01/22] gpiolib: move gpiolib-sysfs function declarations into their own header Kent Gibson
2020-06-24 13:34 ` Bartosz Golaszewski
2020-06-24 13:38 ` Kent Gibson
2020-06-23 4:00 ` [PATCH 02/22] gpiolib: cdev: sort includes Kent Gibson
2020-06-24 13:34 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 03/22] gpiolib: cdev: minor indentation fixes Kent Gibson
2020-06-24 13:35 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 04/22] gpiolib: cdev: refactor gpiohandle_flags_to_desc_flags Kent Gibson
2020-06-24 13:51 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 05/22] gpiolib: cdev: rename 'filep' and 'filp' to 'file' to be consistent with other use Kent Gibson
2020-06-24 13:52 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 06/22] gpiolib: cdev: rename numdescs to num_descs Kent Gibson
2020-06-24 13:53 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 07/22] gpiolib: cdev: remove pointless decrement of i Kent Gibson
2020-06-24 13:53 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 08/22] gpiolib: cdev: complete the irq/thread timestamp handshake Kent Gibson
2020-06-24 14:00 ` Bartosz Golaszewski
2020-06-24 14:08 ` Kent Gibson
2020-06-25 9:44 ` Bartosz Golaszewski
2020-06-25 10:01 ` Kent Gibson
2020-06-30 9:08 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 09/22] gpiolib: cdev: rename priv to gcdev Kent Gibson
2020-06-24 14:04 ` Bartosz Golaszewski
2020-06-24 14:19 ` Kent Gibson
2020-06-24 14:20 ` Bartosz Golaszewski
2020-06-24 23:16 ` Kent Gibson
2020-06-25 10:26 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 10/22] gpiolib: cdev: fix minor race in GET_LINEINFO_WATCH Kent Gibson
2020-06-24 14:05 ` Bartosz Golaszewski
2020-06-24 14:46 ` Andy Shevchenko
2020-06-24 15:57 ` Kent Gibson
2020-06-24 22:58 ` Kent Gibson
2020-06-25 8:44 ` Andy Shevchenko
2020-06-25 9:13 ` Kent Gibson
2020-06-25 9:23 ` Andy Shevchenko
2020-06-25 9:36 ` Kent Gibson [this message]
2020-06-23 4:00 ` [PATCH 11/22] gpiolib: cdev: remove recalculation of offset Kent Gibson
2020-06-30 8:56 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 12/22] gpio: uapi: define GPIO_MAX_NAME_SIZE for array sizes Kent Gibson
2020-06-24 14:13 ` Bartosz Golaszewski
2020-06-23 4:00 ` [PATCH 13/22] gpio: uapi: define uAPI V2 Kent Gibson
2020-06-24 14:33 ` Andy Shevchenko
2020-06-24 15:40 ` Kent Gibson
2020-06-26 14:02 ` Kent Gibson
2020-06-24 14:36 ` Bartosz Golaszewski
2020-06-24 23:58 ` Kent Gibson
2020-06-23 4:00 ` [PATCH 14/22] gpiolib: make cdev a build option Kent Gibson
2020-06-29 14:25 ` Bartosz Golaszewski
2020-06-23 4:01 ` [PATCH 15/22] gpiolib: add build option for CDEV V1 ABI Kent Gibson
2020-06-29 14:26 ` Bartosz Golaszewski
2020-06-23 4:01 ` [PATCH 16/22] gpiolib: cdev: add V2 uAPI implementation to parity with V1 Kent Gibson
2020-06-23 17:44 ` Dan Carpenter
2020-06-23 23:23 ` Kent Gibson
2020-06-23 4:01 ` [PATCH 17/22] gpiolib: cdev: report edge detection in lineinfo Kent Gibson
2020-06-23 4:01 ` [PATCH 18/22] gpiolib: cdev: support setting debounce Kent Gibson
2020-06-23 4:01 ` [PATCH 19/22] gpio: uapi: document uAPI V1 as deprecated Kent Gibson
2020-06-23 4:01 ` [PATCH 20/22] tools: gpio: switch tools to V2 uAPI Kent Gibson
2020-06-23 4:01 ` [PATCH 21/22] tools: gpio: add debounce support to gpio-event-mon Kent Gibson
2020-06-23 4:01 ` [PATCH 22/22] tools: gpio: support monitoring multiple lines Kent Gibson
2020-06-30 10:43 ` Bartosz Golaszewski
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