From patchwork Wed Oct 25 13:07:29 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: George Stark X-Patchwork-Id: 738569 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 B3B65C25B70 for ; Wed, 25 Oct 2023 13:07:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234960AbjJYNHz (ORCPT ); Wed, 25 Oct 2023 09:07:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234952AbjJYNHx (ORCPT ); Wed, 25 Oct 2023 09:07:53 -0400 Received: from mx1.sberdevices.ru (mx1.sberdevices.ru [37.18.73.165]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 70DC5116; Wed, 25 Oct 2023 06:07:47 -0700 (PDT) Received: from p-infra-ksmg-sc-msk01 (localhost [127.0.0.1]) by mx1.sberdevices.ru (Postfix) with ESMTP id 667BE10003F; Wed, 25 Oct 2023 16:07:44 +0300 (MSK) DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.sberdevices.ru 667BE10003F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=salutedevices.com; s=mail; t=1698239264; bh=yGub9+Dsp9bk1acBBB0/yAlR8ZzAfw6sZjBF08zOdpU=; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type:From; b=s4EP/TnfUb8IXrOlVO//TgpOfTSDBG+Z+BupDUdIDF4DstolYt1F8kT5getb3vo/v Bmy7SwjJb7ThjM6IhKaxIjjDZsqZonF/QV18hXnUWatQvWRYf5mA0Is2cA3hNNcK1U phiXb4HwBMu81Q05o/V3t3ENkXUzgZzw5zaHTbo06EMUPjKpXUaKxQvPmwzUsEgvyM qkcKPnKtKzHGjduuCKmuSVgfvCAkJM04Rb8aOOpc7o5AiM6v7fEt2KrwlsJ+EcEVcm 8tSPkAhUdpoFrPGRlsflj/Q3iF2v8leMoMNgKzrnZQSRIfs127bnTYk19IAP4QW8Op PkfyBfHAvf2XQ== 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; Wed, 25 Oct 2023 16:07:44 +0300 (MSK) Received: from localhost.localdomain (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; Wed, 25 Oct 2023 16:07:43 +0300 From: George Stark To: , , , , , , CC: , , , Subject: [PATCH 0/8] devm_led_classdev_register() usage problem Date: Wed, 25 Oct 2023 16:07:29 +0300 Message-ID: <20231025130737.2015468-1-gnstark@salutedevices.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 X-Originating-IP: [100.64.160.123] X-ClientProxiedBy: p-i-exch-sc-m01.sberdevices.ru (172.16.192.107) 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: 180883 [Oct 25 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}, 127.0.0.199:7.1.2; d41d8cd98f00b204e9800998ecf8427e.com:7.1.1; 100.64.160.123:7.1.2; p-i-exch-sc-m01.sberdevices.ru:7.1.1,5.0.1; salutedevices.com:7.1.1, 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: 2023/10/25 11:29:00 #22291710 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org 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(-)