Messages in this thread | | | Date | Tue, 8 Aug 2023 20:23:40 +0300 | From | Andy Shevchenko <> | Subject | Re: [PATCH v2] gpio: consumer: new virtual driver |
| |
On Tue, Aug 08, 2023 at 04:56:05PM +0200, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > 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.
I'll read documentation later. Some code comments below.
...
> +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 == 0 ? 1 : 0;
Can be
timer_data->val = timer_data->val ? 0 : 1;
But again, why not
timer_data->val ^= 1;
?
> + gpiod_set_value_cansleep(timer_data->desc, timer_data->val); > + mod_timer(&timer_data->timer, jiffies + msecs_to_jiffies(1000)); > +}
...
> + key = kstrndup(page, count, GFP_KERNEL); > + if (!key) > + return -ENOMEM;
> + stripped = strstrip(key); > + memmove(key, stripped, strlen(stripped) + 1);
This can be avoided by
key = kstrndup(skip_spaces(page), count, GFP_KERNEL);
no?
...
> + ret = kstrtoint(page, 0, &offset); > + if (ret) > + return ret; > + > + /* Use -1 to indicate lookup by name. */
This comment is unclear as offset can be -1 given by the user. What does above mean in that context?
> + if (offset > (U16_MAX - 1))
And how does it related to this -1 if related at all?
> + return -EINVAL;
...
> +static struct config_group * > +gpio_consumer_config_make_device_group(struct config_group *group, > + const char *name) > +{ > + struct gpio_consumer_device *dev; > + > + dev = kzalloc(sizeof(*dev), GFP_KERNEL); > + if (!dev) > + return ERR_PTR(-ENOMEM); > + > + dev->id = ida_alloc(&gpio_consumer_ida, GFP_KERNEL); > + if (dev->id < 0) { > + kfree(dev);
Wondering if you can utilize cleanup.h.
> + return ERR_PTR(dev->id); > + } > + > + config_group_init_type_name(&dev->group, name, > + &gpio_consumer_device_config_group_type); > + mutex_init(&dev->lock); > + INIT_LIST_HEAD(&dev->lookup_list); > + dev->bus_notifier.notifier_call = gpio_consumer_bus_notifier_call; > + dev->function = GPIO_CONSUMER_FUNCTION_ACTIVE; > + init_completion(&dev->probe_completion); > + > + return &dev->group; > +}
-- With Best Regards, Andy Shevchenko
| |