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 61123C4167B for ; Sat, 4 Nov 2023 07:18:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231278AbjKDHSI (ORCPT ); Sat, 4 Nov 2023 03:18:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229509AbjKDHSF (ORCPT ); Sat, 4 Nov 2023 03:18:05 -0400 Received: from mx1.sberdevices.ru (mx1.sberdevices.ru [37.18.73.165]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4067A1BD; Sat, 4 Nov 2023 00:18:00 -0700 (PDT) Received: from p-infra-ksmg-sc-msk01 (localhost [127.0.0.1]) by mx1.sberdevices.ru (Postfix) with ESMTP id 865AE100007; Sat, 4 Nov 2023 10:17:55 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.sberdevices.ru 865AE100007 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=salutedevices.com; s=mail; t=1699082275; bh=s8uqfl8o3FZrVyh0mvXJUoUOdcz1xIKqtqL+86amnUo=; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type:From; b=X+EJuDdVuaj/VCrb7v34vATJL7RAnLnG/Q0ViA2g07CMEb0bupDIZ0qns4Lm/rOUM jV2eQ1/DJJNLwhS/+bPGSrgRCu3g7dzxkonh5Pj9NsziBW44oP+GWVDjp1q77IdJ9u V4ZhxfFhwWHiu7dg8sWh87DP0gumG7J4LN+Fkl4I4jbaY76Y1oxaBtNVqq/1F0XiRR oNtShqPS5VJReEPP9/bkt7EkUdyCPLeFTT2oBjGGRfyxbj0VBODutuJY8f7y2FXNm7 NTsBmFqm1r1PnWNum5YANIjVZCUErckbeKmGLNiCxAmu/LzhOjCkRfRjEN5nqjWji1 T0adKEWsd+eDQ== Received: from p-i-exch-sc-m01.sberdevices.ru (p-i-exch-sc-m01.sberdevices.ru [172.16.192.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.sberdevices.ru (Postfix) with ESMTPS; Sat, 4 Nov 2023 10:17:54 +0300 (MSK) Received: from [192.168.1.127] (100.64.160.123) by p-i-exch-sc-m01.sberdevices.ru (172.16.192.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.37; Sat, 4 Nov 2023 10:17:54 +0300 Message-ID: <8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com> Date: Sat, 4 Nov 2023 10:18:13 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/8] devm_led_classdev_register() usage problem Content-Language: en-US To: "andy.shevchenko@gmail.com" CC: , , , , , , , , , References: <20231025130737.2015468-1-gnstark@salutedevices.com> From: George Stark In-Reply-To: <20231025130737.2015468-1-gnstark@salutedevices.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [100.64.160.123] X-ClientProxiedBy: p-i-exch-sc-m02.sberdevices.ru (172.16.192.103) To p-i-exch-sc-m01.sberdevices.ru (172.16.192.107) X-KSMG-Rule-ID: 10 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Lua-Profiles: 181122 [Nov 03 2023] X-KSMG-AntiSpam-Version: 6.0.0.2 X-KSMG-AntiSpam-Envelope-From: gnstark@salutedevices.com X-KSMG-AntiSpam-Rate: 0 X-KSMG-AntiSpam-Status: not_detected X-KSMG-AntiSpam-Method: none X-KSMG-AntiSpam-Auth: dkim=none X-KSMG-AntiSpam-Info: LuaCore: 543 543 1e3516af5cdd92079dfeb0e292c8747a62cb1ee4, {Tracking_from_domain_doesnt_match_to}, salutedevices.com:7.1.1;p-i-exch-sc-m01.sberdevices.ru:5.0.1,7.1.1;127.0.0.199:7.1.2;d41d8cd98f00b204e9800998ecf8427e.com:7.1.1;100.64.160.123:7.1.2, FromAlignment: s, ApMailHostAddress: 100.64.160.123 X-MS-Exchange-Organization-SCL: -1 X-KSMG-AntiSpam-Interceptor-Info: scan successful X-KSMG-AntiPhishing: Clean X-KSMG-LinksScanning: Clean X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 2.0.1.6960, bases: 2023/11/04 06:10:00 #22399920 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Andy Could you please take a look at this patch series? I've just found your post on habr about devres API misusing and I think this is just another case. On 10/25/23 16:07, George Stark wrote: > Lots of drivers use devm_led_classdev_register() to register their led objects > and let the kernel free those leds at the driver's remove stage. > It can lead to a problem due to led_classdev_unregister() > implementation calls led_set_brightness() to turn off the led. > led_set_brightness() may call one of the module's brightness_set callbacks. > If that callback uses module's resources allocated without using devm funcs() > then those resources will be already freed at module's remove() callback and > we may have use-after-free situation. > > Here is an example: > > module_probe() > { > devm_led_classdev_register(module_brightness_set_cb); > mutex_init(&mutex); > } > > module_brightness_set_cb() > { > mutex_lock(&mutex); > do_set_brightness(); > mutex_unlock(&mutex); > } > > module_remove() > { > mutex_destroy(&mutex); > } > > at rmmod: > module_remove() > ->mutex_destroy(&mutex); > devres_release_all() > ->led_classdev_unregister(); > ->led_set_brightness(); > ->module_brightness_set_cb(); > ->mutex_lock(&mutex); /* use-after-free */ > > I think it's an architectural issue and should be discussed thoroughly. > Some thoughts about fixing it as a start: > 1) drivers can use devm_led_classdev_unregister() to explicitly free leds before > dependend resources are freed. devm_led_classdev_register() remains being useful > to simplify probe implementation. > As a proof of concept I examined all drivers from drivers/leds and prepared > patches where it's needed. Sometimes it was not as clean as just calling > devm_led_classdev_unregister() because several drivers do not track > their leds object at all - they can call devm_led_classdev_register() and drop the > returned pointer. In that case I used devres group API. > > Drivers outside drivers/leds should be checked too after discussion. > > 2) remove led_set_brightness from led_classdev_unregister() and force the drivers > to turn leds off at shutdown. May be add check that led's brightness is 0 > at led_classdev_unregister() and put a warning to dmesg if it's not. > Actually in many cases it doesn't really need to turn off the leds manually one-by-one > if driver shutdowns whole led controller. For the last case to disable the warning > new flag can be brought in e.g LED_AUTO_OFF_AT_SHUTDOWN (similar to LED_RETAIN_AT_SHUTDOWN). > > George Stark (8): > leds: powernv: explicitly unregister LEDs at module's shutdown > leds: nic78bx: explicitly unregister LEDs at module's shutdown > leds: an30259a: explicitly unregister LEDs at module's shutdown > leds: mlxreg: explicitly unregister LEDs at module's shutdown > leds: aw200xx: explicitly unregister LEDs at module's shutdown > leds: aw2013: explicitly unregister LEDs at module's shutdown > leds: lp3952: explicitly unregister LEDs at module's shutdown > leds: lm3532: explicitly unregister LEDs at module's shutdown > > drivers/leds/leds-an30259a.c | 4 ++++ > drivers/leds/leds-aw200xx.c | 4 ++++ > drivers/leds/leds-aw2013.c | 4 ++++ > drivers/leds/leds-lm3532.c | 6 ++++++ > drivers/leds/leds-lp3952.c | 5 +++++ > drivers/leds/leds-mlxreg.c | 12 +++++++++++- > drivers/leds/leds-nic78bx.c | 4 ++++ > drivers/leds/leds-powernv.c | 7 +++++++ > 8 files changed, 45 insertions(+), 1 deletion(-) > -- Best regards George