[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZNT8T1n0IeJ1uzl6@smile.fi.intel.com>
Date: Thu, 10 Aug 2023 18:03:43 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>,
Kent Gibson <warthog618@...il.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v3] gpio: consumer: new virtual driver
On Wed, Aug 09, 2023 at 04:27:09PM +0200, Bartosz Golaszewski wrote:
>
> The GPIO subsystem has a serious problem with undefined behavior and
> use-after-free bugs on hot-unplug of GPIO chips. This can be considered a
> corner-case by some as most GPIO controllers are enabled early in the
> boot process and live until the system goes down but most GPIO drivers
> do allow unbind over sysfs, many are loadable modules that can be (force)
> unloaded and there are also GPIO devices that can be dynamically detached,
> for instance CP2112 which is a USB GPIO expender.
>
> Bugs can be triggered both from user-space as well as by in-kernel users.
> We have the means of testing it from user-space via the character device
> but the issues manifest themselves differently in the kernel.
>
> This is a proposition of adding a new virtual driver - a configurable
> GPIO consumer that can be configured over configfs (similarly to
> gpio-sim).
>
> The configfs interface allows users to create dynamic GPIO lookup tables
> that are registered with the GPIO subsystem. Every config group
> represents a consumer device. Every sub-group represents a single GPIO
> lookup. The device can work in three modes: just keeping the line
> active, toggling it every second or requesting its interrupt and
> reporting edges. Every lookup allows to specify the key, offset and
> flags as per the lookup struct defined in linux/gpio/machine.h.
>
> The module together with gpio-sim allows to easily trigger kernel
> hot-unplug errors. A simple use-case is to create a simulated chip,
> setup the consumer to lookup one of its lines in 'monitor' mode, unbind
> the simulator, unbind the consumer and observe the fireworks in dmesg.
>
> This driver is aimed as a helper in tackling the hot-unplug problem in
> GPIO as well as basis for future regression testing once the fixes are
> upstream.
...
> +static void gpio_consumer_on_timer(struct timer_list *timer)
> +{
> + struct gpio_consumer_timer_data *timer_data = to_timer_data(timer);
> +
> + timer_data->val = timer_data->val ? 1 : 0;
I guess it should be 0 : 1.
> + gpiod_set_value_cansleep(timer_data->desc, timer_data->val);
> + mod_timer(&timer_data->timer, jiffies + msecs_to_jiffies(1000));
> +}
...
> +static ssize_t
> +gpio_consumer_lookup_config_key_show(struct config_item *item, char *page)
> +{
> + struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
> + struct gpio_consumer_device *dev = lookup->parent;
> + int ret;
Why is it needed now? Seems you were too fast to send v3, look at my comments
in v2 thread.
> + scoped_guard(mutex, &dev->lock)
> + ret = sprintf(page, "%s\n", lookup->key);
> +
> + return ret;
> +}
...
> +static ssize_t
> +gpio_consumer_lookup_config_key_store(struct config_item *item,
> + const char *page, size_t count)
> +{
> + struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
> + struct gpio_consumer_device *dev = lookup->parent;
> + char *key __free(kfree) = NULL;
> + char *stripped;
> +
> + key = kstrndup(page, count, GFP_KERNEL);
skip_spaces() will allow you to get rid of memmove().
> + if (!key)
> + return -ENOMEM;
> +
> + stripped = strstrip(key);
> + memmove(key, stripped, strlen(stripped) + 1);
And this become something like
/* Get rid of trailing newline and spaces */
strim(key);
> + guard(mutex)(&dev->lock);
> +
> + if (gpio_consumer_device_is_live_unlocked(dev))
> + return -EBUSY;
> +
> + kfree(lookup->key);
> + lookup->key = no_free_ptr(key);
> +
> + return count;
> +}
...
> +static enum gpio_lookup_flags
> +gpio_consumer_lookup_get_flags(struct config_item *item)
> +{
> + struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
> + struct gpio_consumer_device *dev = lookup->parent;
> + enum gpio_lookup_flags flags;
> +
> + scoped_guard(mutex, &dev->lock)
> + flags = lookup->flags;
> +
> + return flags;
guard()
return lookup->flags;
?
> +}
...
> +static ssize_t
> +gpio_consumer_device_config_live_store(struct config_item *item,
> + const char *page, size_t count)
> +{
> + struct gpio_consumer_device *dev = to_gpio_consumer_device(item);
> + bool live;
> + int ret;
> +
> + ret = kstrtobool(page, &live);
> + if (ret)
> + return ret;
> +
> + guard(mutex)(&dev->lock);
> +
> + if (live == gpio_consumer_device_is_live_unlocked(dev))
> + ret = -EPERM;
return ... ?
> + else if (live)
if () ?
> + ret = gpio_consumer_device_activate_unlocked(dev);
> + else
drop it ?
> + gpio_consumer_device_deactivate_unlocked(dev);
> +
> + return ret ?: count;
> +}
--
With Best Regards,
Andy Shevchenko
Powered by blists - more mailing lists