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 50E1AC4332F for ; Mon, 12 Dec 2022 22:13:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232254AbiLLWNz (ORCPT ); Mon, 12 Dec 2022 17:13:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233476AbiLLWNv (ORCPT ); Mon, 12 Dec 2022 17:13:51 -0500 Received: from mail-pj1-x1036.google.com (mail-pj1-x1036.google.com [IPv6:2607:f8b0:4864:20::1036]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F3321A232; Mon, 12 Dec 2022 14:13:50 -0800 (PST) Received: by mail-pj1-x1036.google.com with SMTP id gt4so1332634pjb.1; Mon, 12 Dec 2022 14:13:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=n2XZBEP0JR3u42vjkud6u2pf7wcC2jLfekfdtsMKR2o=; b=CFHCFDtE98y5A8aGdBtghjU5l9CphTqaYy8+bNqMg2oj+xvRkpTz+CiNOXnOGa+xmH aFRyuXYMB56A8Qaj2sKuwGcPdNQ8AoKGDqpSvvk1nupxWCQ6HeVJMNeCoCndqgy4KHMa gtTajfL2mnJdmGIF83EGfF+l6DuCgA8QoD2TcFhwAK1WOdR4yW8jtgwKhOVlWo2htGf2 5VbW7laZOO8WJeDhfUU061bT5bwJcSuhhe/E7n8AUutbCBMyf/ER4mfE68WrEqJxoo3a 6h3bRzsp+lesOssSJTDJcFigURcJGHNh6iZ62bkwx4gVc0a+Cg6S4v/6y1LTDsSJtivC 4Slg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=n2XZBEP0JR3u42vjkud6u2pf7wcC2jLfekfdtsMKR2o=; b=yr9pfWf4kDhLvyvVeZvMHFhe9i++qnF7ZY1ko2LAtz0mzB7opjeuu9/lb9XhM/29rK HyJ1k3TZdoW7QRFQvCDtFeBi8lYvwoFUvX09WmAjLx0M2s07RiWHo/Qc9bTD4Y7fkOKh 8PJzdRFkLi1ehXNhS06W3TcC+uc/P/rWj+brvrN9QQMu187L7KgBIEJb6ehIbVaScwLv cQ2zKqydLzn0XhLE8SKmOBBaHspHUagEmav789Q0Scj5N43FfYSv296Pd/ozkp1oU6D7 wt9rYep5VD87ssv1U0sOpHk2VJkk/fn+4kHBjPDUR1wlKeARTO5CGs6lDGN5O23iQc/f YCrA== X-Gm-Message-State: ANoB5pmsKokylVe94ZRK3+INeVfHnz9ncE4Vpt4lVWs2aY/y7X8ENm1Y fiAABasnnhk1XKr45O6YRbb2EBoWVJoLWA== X-Google-Smtp-Source: AA0mqf67w1m5VItBX9PGVatqIjNwsKAAmChP+SvVKw5BDzUrHAocCOyWg7+eIfj//6EU5zpEYbFhbQ== X-Received: by 2002:a05:6a20:8e02:b0:a0:462f:8e3f with SMTP id y2-20020a056a208e0200b000a0462f8e3fmr31554587pzj.53.1670883229447; Mon, 12 Dec 2022 14:13:49 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id z29-20020aa7991d000000b00575afe3c188sm6255061pff.150.2022.12.12.14.13.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 14:13:48 -0800 (PST) Sender: Tejun Heo Date: Mon, 12 Dec 2022 12:13:47 -1000 From: Tejun Heo To: Waiman Long Cc: Jens Axboe , Josef Bacik , Zefan Li , Johannes Weiner , Andrew Morton , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal =?iso-8859-1?Q?Koutn=FD?= , "Dennis Zhou (Facebook)" , Yi Zhang Subject: Re: [PATCH-block v2 1/3] bdi, blk-cgroup: Fix potential UAF of blkcg Message-ID: References: <20221211222058.2946830-1-longman@redhat.com> <20221211222058.2946830-2-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221211222058.2946830-2-longman@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Dec 11, 2022 at 05:20:56PM -0500, Waiman Long wrote: > static void blkcg_destroy_blkgs(struct blkcg *blkcg) > { > + /* > + * blkcg_destroy_blkgs() shouldn't be called with all the blkcg > + * references gone. > + */ > + if (WARN_ON_ONCE(!css_tryget(&blkcg->css))) > + return; Wouldn't it make more sense to use percpu_ref_is_zero()? It's not like the obtained extra reference does anything, right? Thanks. -- tejun