From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8026C001B0 for ; Thu, 10 Aug 2023 15:03:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235968AbjHJPDv (ORCPT ); Thu, 10 Aug 2023 11:03:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57366 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231825AbjHJPDu (ORCPT ); Thu, 10 Aug 2023 11:03:50 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E43526A0; Thu, 10 Aug 2023 08:03:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1691679829; x=1723215829; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=V85F3zyG99YKOhkzHvVj9aWIEqnjsPogkM5v3EvHQhU=; b=jS/trbSfnR3Iu5igLTKdKt39ENvnkayFi6TQAAUYRLVCfy7h+k8AH0Ej kB+dD4oftltZkRZoC9a5YHEeBslFLM3dJLTekldkhTUErKrLbIZ7CWBD7 wQNXKIv5ZQ9FuFqze+116fHzbNbNgAXcE89jXT54qYQFy2RUTGJj14ZLb rS6f4fh2/llbb2PxAM12pM22GwCRHP+kZqLqQhEpjtVd95VLW43+QYEnc Qg0SdNVYQsvOyRgUN7GP0nyhRf2hLlcTsKBFHQT3I0yxtX5QgeXtVfjLu kznLRTUmuXaJHVoahtX4eAmjTuksRiJCfkTDpW2+XYCbBPi1oMq7etvvF g==; X-IronPort-AV: E=McAfee;i="6600,9927,10798"; a="375138428" X-IronPort-AV: E=Sophos;i="6.01,162,1684825200"; d="scan'208";a="375138428" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2023 08:03:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10798"; a="732289598" X-IronPort-AV: E=Sophos;i="6.01,162,1684825200"; d="scan'208";a="732289598" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga002.jf.intel.com with ESMTP; 10 Aug 2023 08:03:45 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1qU7CS-00625D-00; Thu, 10 Aug 2023 18:03:44 +0300 Date: Thu, 10 Aug 2023 18:03:43 +0300 From: Andy Shevchenko To: Bartosz Golaszewski Cc: Linus Walleij , Kent Gibson , Viresh Kumar , Geert Uytterhoeven , linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: Re: [PATCH v3] gpio: consumer: new virtual driver Message-ID: References: <20230809142709.28042-1-brgl@bgdev.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230809142709.28042-1-brgl@bgdev.pl> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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