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 X-Spam-Level: X-Spam-Status: No, score=-14.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1ACB4C433E1 for ; Thu, 27 Aug 2020 20:33:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E60F920848 for ; Thu, 27 Aug 2020 20:33:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="RWeorijv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726322AbgH0UdF (ORCPT ); Thu, 27 Aug 2020 16:33:05 -0400 Received: from lelv0142.ext.ti.com ([198.47.23.249]:49568 "EHLO lelv0142.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726120AbgH0UdE (ORCPT ); Thu, 27 Aug 2020 16:33:04 -0400 Received: from lelv0266.itg.ti.com ([10.180.67.225]) by lelv0142.ext.ti.com (8.15.2/8.15.2) with ESMTP id 07RKW898076324; Thu, 27 Aug 2020 15:32:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1598560328; bh=aYp1+3+GIhxsev2f1k2D7ETcN46E5m3qO75FVMnA180=; h=Subject:To:CC:References:From:Date:In-Reply-To; b=RWeorijvGe6nawyg39RIAjSMoLml/oNcTmDHjCMtBE3mWY4mgcypA7J3qCEmonjNB gewW5pvg1thGKxlk5TRpiwYVjtPehdnuZuAKXx9m1XDRT0oMgATYYmV+nI/IlepRYG 8uqygl/ETJpwFZ6jpASwmIqoo4A/pncbK+aTK0+8= Received: from DLEE113.ent.ti.com (dlee113.ent.ti.com [157.170.170.24]) by lelv0266.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 07RKW8Wl064212 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 27 Aug 2020 15:32:08 -0500 Received: from DLEE100.ent.ti.com (157.170.170.30) by DLEE113.ent.ti.com (157.170.170.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3; Thu, 27 Aug 2020 15:32:07 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DLEE100.ent.ti.com (157.170.170.30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3 via Frontend Transport; Thu, 27 Aug 2020 15:32:07 -0500 Received: from [10.250.69.147] (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 07RKW5WY114954; Thu, 27 Aug 2020 15:32:06 -0500 Subject: Re: [RESEND PATCH v2] mfd: syscon: Use a unique name with regmap_config To: Marc Zyngier , Mark Brown CC: Lee Jones , Arnd Bergmann , Grzegorz Jaszczyk , David Lechner , Tony Lindgren , , , , Roger Quadros , References: <20200727211008.24225-1-s-anna@ti.com> <0c1feaf91b9d285c1bded488437705da@misterjones.org> <74bc1f9f-cc48-cec9-85f4-3376b66b40fc@ti.com> <78b465b080772b6ba867e39a623c2310@kernel.org> From: Suman Anna Message-ID: Date: Thu, 27 Aug 2020 15:32:05 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <78b465b080772b6ba867e39a623c2310@kernel.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org Hi Marc, + Mark Brown On 8/27/20 3:06 PM, Marc Zyngier wrote: > Hi Suman, > > On 2020-08-27 19:28, Suman Anna wrote: >> Hi Marc, >> >> On 8/27/20 9:46 AM, Marc Zyngier wrote: >>> Hi all, >>> >>> On 2020-07-27 22:10, Suman Anna wrote: >>>> The DT node full name is currently being used in regmap_config >>>> which in turn is used to create the regmap debugfs directories. >>>> This name however is not guaranteed to be unique and the regmap >>>> debugfs registration can fail in the cases where the syscon nodes >>>> have the same unit-address but are present in different DT node >>>> hierarchies. Replace this logic using the syscon reg resource >>>> address instead (inspired from logic used while creating platform >>>> devices) to ensure a unique name is given for each syscon. >>>> >>>> Signed-off-by: Suman Anna >>>> --- >>>> Hi Arnd, >>>> Lee is looking for your review on this patch. Can you please >>>> review and provide your comments. >>>> >>>> This is a resend of the patch that was posted previously, rebased >>>> now onto latest kernel. >>>> >>>> v2: https://patchwork.kernel.org/patch/11353355/ >>>>  - Fix build warning reported by kbuild test bot >>>> v1: https://patchwork.kernel.org/patch/11346363/ >>>> >>>>  drivers/mfd/syscon.c | 4 +++- >>>>  1 file changed, 3 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c >>>> index 3a97816d0cba..75859e492984 100644 >>>> --- a/drivers/mfd/syscon.c >>>> +++ b/drivers/mfd/syscon.c >>>> @@ -101,12 +101,14 @@ static struct syscon *of_syscon_register(struct >>>> device_node *np, bool check_clk) >>>>          } >>>>      } >>>> >>>> -    syscon_config.name = of_node_full_name(np); >>>> +    syscon_config.name = kasprintf(GFP_KERNEL, "%pOFn@%llx", np, >>>> +                       (u64)res.start); >>>>      syscon_config.reg_stride = reg_io_width; >>>>      syscon_config.val_bits = reg_io_width * 8; >>>>      syscon_config.max_register = resource_size(&res) - reg_io_width; >>>> >>>>      regmap = regmap_init_mmio(NULL, base, &syscon_config); >>>> +    kfree(syscon_config.name); >>>>      if (IS_ERR(regmap)) { >>>>          pr_err("regmap init failed\n"); >>>>          ret = PTR_ERR(regmap); >>> >>> This patch triggers some illegal memory accesses when debugfs is >>> enabled, as regmap does rely on config->name to be persistent >>> when the debugfs registration is deferred via regmap_debugfs_early_list >>> (__regmap_init() -> regmap_attach_dev() -> regmap_debugfs_init()...), >>> leading to a KASAN splat on demand. >>> >> >> Thanks, I missed the subtlety around the debugfs registration. >> >>> I came up with the following patch that solves the issue for me. >>> >>> Thanks, >>> >>>         M. >>> >>> From fd3f5f2bf72df53be18d13914fe349a34f81f16b Mon Sep 17 00:00:00 2001 >>> From: Marc Zyngier >>> Date: Thu, 27 Aug 2020 14:45:34 +0100 >>> Subject: [PATCH] mfd: syscon: Don't free allocated name for regmap_config >>> >>> The name allocated for the regmap_config structure is freed >>> pretty early, right after the registration of the MMIO region. >>> >>> Unfortunately, that doesn't follow the life cycle that debugfs >>> expects, as it can access the name field long after the free >>> has occured. >>> >>> Move the free on the error path, and keep it forever otherwise. >> >> Hmm, this is exactly what I was trying to avoid. The regmap_init does duplicate >> the name into map->name if config->name is given, and the regmap debugfs makes >> another copy of its own into debugfs_name when actually registered. If the rules >> for regmap_init is that the config->name should be persistent, then I guess we >> have no choice but to go with the below fix. >> >> Does something like below help? >> >> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c >> index e93700af7e6e..96d8a0161c89 100644 >> --- a/drivers/base/regmap/regmap.c >> +++ b/drivers/base/regmap/regmap.c >> @@ -1137,7 +1137,7 @@ struct regmap *__regmap_init(struct device *dev, >>                 if (ret != 0) >>                         goto err_regcache; >>         } else { >> -               regmap_debugfs_init(map, config->name); >> +               regmap_debugfs_init(map, map->name); >> >> But there are couple of other places in regmap code that uses config->name, but >> those won't be exercised with the syscon code. > > Is config->name always the same as map->name? If so, why don't you just > pass map once and for all? Is the lifetime of map->name the same as > that of config->name? map->name is created (kstrdup_const) from config->name if not NULL, so above replacement should be exactly equivalent, map is filled in _regmap_init. But it does make the regmap_debugfs_init callsites in the file look dissimilar. > > My worry with this approach is that we start changing stuff in a rush, > and this would IMHO deserve a thorough investigation of whether this > change is actually safe. > > I'd rather take the safe approach of either keeping the memory around > until we clearly understand what the implications are (and probably > this should involve the regmap maintainer), or to revert this patch > until we figure out the actual life cycle of the various names. Yeah, agreed. Let's see what Mark suggests. Mark, Can you clarify the lifecycle expectations on the config->name and do you have any suggestions here? regards Suman