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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 6D98DC43387 for ; Tue, 18 Dec 2018 18:57:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3244421873 for ; Tue, 18 Dec 2018 18:57:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Y8Y3UnCj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726850AbeLRS5m (ORCPT ); Tue, 18 Dec 2018 13:57:42 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:38900 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726630AbeLRS5m (ORCPT ); Tue, 18 Dec 2018 13:57:42 -0500 Received: by mail-pg1-f196.google.com with SMTP id g189so8220100pgc.5; Tue, 18 Dec 2018 10:57:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=PjGvbnfLhPPm0SXuTZwSXCShHgZC59Z+ZbinXYEiYTs=; b=Y8Y3UnCjUXV1Q6D/GQNvBx801eNl6axxfPaRiHADiu0HhnvGSyA2fkRoBziYcQ7Wwq gqEZPKIWl+QbgaD48J8xJNvqM4EKJVYNrQWJo9iaPHo0lgbtBnoGnqVRnwEl3mSkeIfu Xvrinz4txoQ4zWSRlTiiRJSfCqYx17ThRLzdkTY38ay/uDj1lMzyw5F9GKRtRpYpeMdI 2cb239brHOQ2i0qYqQy+PgTWbulb9OD3YuC74h+fQlfitrTMW//b/8c6/kcD2RB/vvYQ EQJSTxNw28b7Y48XoAHpiLwVAfJoXakkVvUGYZCpblXF63IpSZJJ/7Js8EvO1LA/bgYi GR3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=PjGvbnfLhPPm0SXuTZwSXCShHgZC59Z+ZbinXYEiYTs=; b=KZSGs2qb7KsaavtL3FU6tCP5XGkbQu1Hq6lOuGP+armeKYYMNjK6dYTb7c9vgCBKiz fQkGJUECsaghuqKiwUIJLXOQuJnNq7dwn7V7PvdaYMVQ8lZzEjgJzsYGBnvQvybKnMPf 7Ao3B+SpYV1OFsH3NthHpGBMm8PUgwXXlVS/CQsWGe0B0FesXkq/BPa0Amu3aWgCsf+z uwzj708XuUm1jTKWN2uSEMK1si+zkVKK4qXk9aOMAjkvUR3JAAG2b3Q300mvB4bokhsZ /VZhQo0nXmnxt7F2JgHlhom8Pj9nCk/Ic0h6CrEXsNbbnMocz5hgkKKpdgaELv2nQe83 +tCw== X-Gm-Message-State: AA+aEWYzORgMxrTq8CwzvqBRPUN6P2zoNIza4XqXL1QRcAeyA6tbKm5y FFobpQatL38+KRWGLNiH3Ho= X-Google-Smtp-Source: AFSGD/USb3bGS65TzadVotpbTeAD9u2bdXqPb2wxYQL69++1fMVq960yXPVtkkNVsAKDzK+boOWKIA== X-Received: by 2002:a62:a510:: with SMTP id v16mr17596135pfm.18.1545159461094; Tue, 18 Dec 2018 10:57:41 -0800 (PST) Received: from [192.168.1.70] (c-24-6-192-50.hsd1.ca.comcast.net. [24.6.192.50]) by smtp.gmail.com with ESMTPSA id p24sm22878563pfk.155.2018.12.18.10.57.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 10:57:40 -0800 (PST) Subject: Re: [PATCH v2 2/2] of: __of_detach_node() - remove node from phandle cache To: Michael Ellerman , robh+dt@kernel.org, Michael Bringmann , linuxppc-dev@lists.ozlabs.org Cc: Tyrel Datwyler , Thomas Falcon , Juliet Kim , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <1545033396-24485-1-git-send-email-frowand.list@gmail.com> <1545033396-24485-3-git-send-email-frowand.list@gmail.com> <871s6gv30z.fsf@concordia.ellerman.id.au> From: Frank Rowand Message-ID: Date: Tue, 18 Dec 2018 10:57:38 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <871s6gv30z.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/17/18 2:52 AM, Michael Ellerman wrote: > Hi Frank, > > frowand.list@gmail.com writes: >> From: Frank Rowand >> >> Non-overlay dynamic devicetree node removal may leave the node in >> the phandle cache. Subsequent calls to of_find_node_by_phandle() >> will incorrectly find the stale entry. Remove the node from the >> cache. >> >> Add paranoia checks in of_find_node_by_phandle() as a second level >> of defense (do not return cached node if detached, do not add node >> to cache if detached). >> >> Reported-by: Michael Bringmann >> Signed-off-by: Frank Rowand >> --- > > Similarly here can we add: > > Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()") Yes, thanks. > Cc: stable@vger.kernel.org # v4.17+ Nope, 0b3ce78e90fc does not belong in stable (it is a feature, not a bug fix). So the bug will not be in stable. I've debated with myself over this, because there is a possibility that 0b3ce78e90fc could somehow be put into a stable despite not being a bug fix. We can always explicitly request this patch series be added to stable in that case. > Thanks for doing this series. > > Some minor comments below. > >> diff --git a/drivers/of/base.c b/drivers/of/base.c >> index 6c33d63361b8..ad71864cecf5 100644 >> --- a/drivers/of/base.c >> +++ b/drivers/of/base.c >> @@ -162,6 +162,27 @@ int of_free_phandle_cache(void) >> late_initcall_sync(of_free_phandle_cache); >> #endif >> >> +/* >> + * Caller must hold devtree_lock. >> + */ >> +void __of_free_phandle_cache_entry(phandle handle) >> +{ >> + phandle masked_handle; >> + >> + if (!handle) >> + return; > > We could fold the phandle_cache check into that if and return early for > both cases couldn't we? We could, but that would make the reason for checking phandle_cache less obvious. I would rather leave that check > >> + masked_handle = handle & phandle_cache_mask; >> + >> + if (phandle_cache) { > > Meaning this wouldn't be necessary. > >> + if (phandle_cache[masked_handle] && >> + handle == phandle_cache[masked_handle]->phandle) { >> + of_node_put(phandle_cache[masked_handle]); >> + phandle_cache[masked_handle] = NULL; >> + } > > A temporary would help the readability here I think, eg: > > struct device_node *np; > np = phandle_cache[masked_handle]; > > if (np && handle == np->phandle) { > of_node_put(np); > phandle_cache[masked_handle] = NULL; > } Yes, much cleaner. >> @@ -1209,11 +1230,18 @@ struct device_node *of_find_node_by_phandle(phandle handle) >> if (phandle_cache[masked_handle] && >> handle == phandle_cache[masked_handle]->phandle) >> np = phandle_cache[masked_handle]; >> + if (np && of_node_check_flag(np, OF_DETACHED)) { >> + WARN_ON(1); >> + of_node_put(np); > > Do we really want to do the put here? > > We're here because something has gone wrong, possibly even memory > corruption such that np is not even pointing at a device node anymore. > So it seems like it would be safer to just leave the ref count alone, > possibly leak a small amount of memory, and NULL out the reference. I like the concept of the code being a little bit paranoid. But the bug that this check is likely to cache is the bug that led to this series -- removing a devicetree node, but failing to remove it from the cache as part of the removal. So I think I'll leave it as is. > > > cheers > Thanks for the thoughts and suggestions! -Frank 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=-6.8 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED 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 2DA43C43387 for ; Tue, 18 Dec 2018 19:00:21 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 623B121873 for ; Tue, 18 Dec 2018 19:00:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Y8Y3UnCj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 623B121873 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43K6m16GzwzDqW1 for ; Wed, 19 Dec 2018 06:00:17 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="Y8Y3UnCj"; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=gmail.com (client-ip=2607:f8b0:4864:20::542; helo=mail-pg1-x542.google.com; envelope-from=frowand.list@gmail.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="Y8Y3UnCj"; dkim-atps=neutral Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43K6j34ZC8zDqTb for ; Wed, 19 Dec 2018 05:57:43 +1100 (AEDT) Received: by mail-pg1-x542.google.com with SMTP id n2so8226784pgm.3 for ; Tue, 18 Dec 2018 10:57:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=PjGvbnfLhPPm0SXuTZwSXCShHgZC59Z+ZbinXYEiYTs=; b=Y8Y3UnCjUXV1Q6D/GQNvBx801eNl6axxfPaRiHADiu0HhnvGSyA2fkRoBziYcQ7Wwq gqEZPKIWl+QbgaD48J8xJNvqM4EKJVYNrQWJo9iaPHo0lgbtBnoGnqVRnwEl3mSkeIfu Xvrinz4txoQ4zWSRlTiiRJSfCqYx17ThRLzdkTY38ay/uDj1lMzyw5F9GKRtRpYpeMdI 2cb239brHOQ2i0qYqQy+PgTWbulb9OD3YuC74h+fQlfitrTMW//b/8c6/kcD2RB/vvYQ EQJSTxNw28b7Y48XoAHpiLwVAfJoXakkVvUGYZCpblXF63IpSZJJ/7Js8EvO1LA/bgYi GR3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=PjGvbnfLhPPm0SXuTZwSXCShHgZC59Z+ZbinXYEiYTs=; b=H+TXT6aqX5kdaN7HvkeOexnTNiX+RHDOHahLF9zX67mfJ4SyH1z1y9XD6FJF4IOLOW 1R8UTcTrzMo8xQQcj/FTNurQJCcCUxYC76v5Z2KnBuXmijtB85b6omG4VAiDh9p/Ai27 a6EP9gYBZULuZubtm3zLSe3wUmSRQX+C52lWSrYfJc4pBw8O4852tGmX5eZnD/MEe9LH Usa9bh4IordroKCLXSZrjEbnV8QIyRDGw0zhFgBjRO6bEChO2E+50+Py2WjPhAFSsKLR 0UjavrrBdJHpB5HmxgD9xF7F5+YnyeROuceu5NhL7r3x3REAyO9hHq9+p9hV5DNZahi0 nH/A== X-Gm-Message-State: AA+aEWZQjJngoOemNa5t0wlFxkye1/yD9cSolsp1wHN9epLl1L/LFasl 9weYcVbPU2xWMeLdghZOfic= X-Google-Smtp-Source: AFSGD/USb3bGS65TzadVotpbTeAD9u2bdXqPb2wxYQL69++1fMVq960yXPVtkkNVsAKDzK+boOWKIA== X-Received: by 2002:a62:a510:: with SMTP id v16mr17596135pfm.18.1545159461094; Tue, 18 Dec 2018 10:57:41 -0800 (PST) Received: from [192.168.1.70] (c-24-6-192-50.hsd1.ca.comcast.net. [24.6.192.50]) by smtp.gmail.com with ESMTPSA id p24sm22878563pfk.155.2018.12.18.10.57.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 10:57:40 -0800 (PST) Subject: Re: [PATCH v2 2/2] of: __of_detach_node() - remove node from phandle cache To: Michael Ellerman , robh+dt@kernel.org, Michael Bringmann , linuxppc-dev@lists.ozlabs.org References: <1545033396-24485-1-git-send-email-frowand.list@gmail.com> <1545033396-24485-3-git-send-email-frowand.list@gmail.com> <871s6gv30z.fsf@concordia.ellerman.id.au> From: Frank Rowand Message-ID: Date: Tue, 18 Dec 2018 10:57:38 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <871s6gv30z.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, Juliet Kim , Thomas Falcon , Tyrel Datwyler , linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 12/17/18 2:52 AM, Michael Ellerman wrote: > Hi Frank, > > frowand.list@gmail.com writes: >> From: Frank Rowand >> >> Non-overlay dynamic devicetree node removal may leave the node in >> the phandle cache. Subsequent calls to of_find_node_by_phandle() >> will incorrectly find the stale entry. Remove the node from the >> cache. >> >> Add paranoia checks in of_find_node_by_phandle() as a second level >> of defense (do not return cached node if detached, do not add node >> to cache if detached). >> >> Reported-by: Michael Bringmann >> Signed-off-by: Frank Rowand >> --- > > Similarly here can we add: > > Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()") Yes, thanks. > Cc: stable@vger.kernel.org # v4.17+ Nope, 0b3ce78e90fc does not belong in stable (it is a feature, not a bug fix). So the bug will not be in stable. I've debated with myself over this, because there is a possibility that 0b3ce78e90fc could somehow be put into a stable despite not being a bug fix. We can always explicitly request this patch series be added to stable in that case. > Thanks for doing this series. > > Some minor comments below. > >> diff --git a/drivers/of/base.c b/drivers/of/base.c >> index 6c33d63361b8..ad71864cecf5 100644 >> --- a/drivers/of/base.c >> +++ b/drivers/of/base.c >> @@ -162,6 +162,27 @@ int of_free_phandle_cache(void) >> late_initcall_sync(of_free_phandle_cache); >> #endif >> >> +/* >> + * Caller must hold devtree_lock. >> + */ >> +void __of_free_phandle_cache_entry(phandle handle) >> +{ >> + phandle masked_handle; >> + >> + if (!handle) >> + return; > > We could fold the phandle_cache check into that if and return early for > both cases couldn't we? We could, but that would make the reason for checking phandle_cache less obvious. I would rather leave that check > >> + masked_handle = handle & phandle_cache_mask; >> + >> + if (phandle_cache) { > > Meaning this wouldn't be necessary. > >> + if (phandle_cache[masked_handle] && >> + handle == phandle_cache[masked_handle]->phandle) { >> + of_node_put(phandle_cache[masked_handle]); >> + phandle_cache[masked_handle] = NULL; >> + } > > A temporary would help the readability here I think, eg: > > struct device_node *np; > np = phandle_cache[masked_handle]; > > if (np && handle == np->phandle) { > of_node_put(np); > phandle_cache[masked_handle] = NULL; > } Yes, much cleaner. >> @@ -1209,11 +1230,18 @@ struct device_node *of_find_node_by_phandle(phandle handle) >> if (phandle_cache[masked_handle] && >> handle == phandle_cache[masked_handle]->phandle) >> np = phandle_cache[masked_handle]; >> + if (np && of_node_check_flag(np, OF_DETACHED)) { >> + WARN_ON(1); >> + of_node_put(np); > > Do we really want to do the put here? > > We're here because something has gone wrong, possibly even memory > corruption such that np is not even pointing at a device node anymore. > So it seems like it would be safer to just leave the ref count alone, > possibly leak a small amount of memory, and NULL out the reference. I like the concept of the code being a little bit paranoid. But the bug that this check is likely to cache is the bug that led to this series -- removing a devicetree node, but failing to remove it from the cache as part of the removal. So I think I'll leave it as is. > > > cheers > Thanks for the thoughts and suggestions! -Frank