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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 EE3DEC352A4 for ; Wed, 12 Feb 2020 21:33:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB0192465D for ; Wed, 12 Feb 2020 21:33:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581543227; bh=bdAJPEhxl47e9iOFyNJ51/ihXyQQQV5GPU9kaQBPvBM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=0bO0w3DPIpPgg8Vx1j2A+cpAwVbLkQDbFI+iQs9LBcUgUSErWTH3/DmLolfYJkU5Y sGU68o8wfGdp4jNB10tZST0iMFpYM2G6I4FBWHhGaXWZoM32eApsusAnGUzTOC26QN RNbK91fWYZPfpnXor9WMCb7vfqKdYWJnswb388UE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727692AbgBLVdr (ORCPT ); Wed, 12 Feb 2020 16:33:47 -0500 Received: from mail-qt1-f194.google.com ([209.85.160.194]:41287 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727564AbgBLVdq (ORCPT ); Wed, 12 Feb 2020 16:33:46 -0500 Received: by mail-qt1-f194.google.com with SMTP id l21so2789047qtr.8 for ; Wed, 12 Feb 2020 13:33:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=CB1ulDKxwf2tqP+HI+yYRfi4ISHZYVmjSyJfHnJrRmQ=; b=XYBgb2D/QSiYyLKz+WU5/HJUkBSXlNqM5+J4mVNuY8V59H/+qg31E2bYLEPHvqvkyq CdVdB03l1WMdiCG6Stup6FaShbB+Gu09yi6DFdQ+FfY8kCvhfMQr0ysGM6a5R/ryIPCU cIZ9XSH8AjizxhdmW+dFH4rP8dLHbsl+GobHWU5AuQoK4PxFSAvvT9M70CnF4TwhBLeH Cg6B5tz1ibbSXtZ6mJRMksWMgp/pAsYVxg4JQ2M3lZMWQeLXglddhOZqnQrQlrTyBC3e RieL+zmOtsfz14/UWbwx7mI6kdSXgj4fE3ccN01eIl2eJtR2SyGCzdZ3dK8KltcRAszD PHUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=CB1ulDKxwf2tqP+HI+yYRfi4ISHZYVmjSyJfHnJrRmQ=; b=D1S3dzO8ZFHnndeanKPWF9SUGtUl/S/VsQtxOWLRMBSdDQFiRGnscJb0ULXGOaPHHF Dz1usB4xvvUo13z9fraEikKyrR1hsFwLZlQdZPiTfS5KtEcFrqYX44AMEoN/7uuPKOOl b5sHNOsu2IUIvq8yvscvITMC/XC9HaBpqO1Z4oqkRux9I10hhxDVnkRzHmxlyd2W2IpR QXS3Df4+5oQi2zl8Eygj7GJJHLlpFWxX1KVuWAr8xFazgzIV+NhQAzaDFxKBUWadQMgT dlpWKti4g4p0NOJM9a5+OH53Iq/Ex+yEvh0+q3c0T8z+85tSCgdW08IlIXBOtGkgZdWI czEA== X-Gm-Message-State: APjAAAUWenJUCfFPx9pVW8p2u5f5l9PQeHXW6A1NOZ8KeZMreTCu3qnf kr5lWjy8ebEr1ttf7rGxbfc= X-Google-Smtp-Source: APXvYqzOJycJV34qt3zPAx8k3/WHi+CbQXH8RYVh9RE2N0I0Y4MJ33HQkoi9MRKE9iTxErIV5C0fEg== X-Received: by 2002:aed:3e53:: with SMTP id m19mr9088468qtf.387.1581543225561; Wed, 12 Feb 2020 13:33:45 -0800 (PST) Received: from localhost ([2620:10d:c091:500::1:985a]) by smtp.gmail.com with ESMTPSA id p135sm109084qke.2.2020.02.12.13.33.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Feb 2020 13:33:44 -0800 (PST) Date: Wed, 12 Feb 2020 16:33:44 -0500 From: Tejun Heo To: Yufen Yu Cc: axboe@kernel.dk, linux-block@vger.kernel.org, jack@suse.cz, bvanassche@acm.org Subject: Re: [PATCH] bdi: fix use-after-free for bdi device Message-ID: <20200212213344.GE80993@mtj.thefacebook.com> References: <20200211140038.146629-1-yuyufen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hello, Yufen. On Tue, Feb 11, 2020 at 09:57:44PM +0800, Yufen Yu wrote: > There is another simple way to fix the problem. > > Since blkg_dev_name() have been coverd by rcu_read_lock/unlock(), > we can wait all rcu reader to finish before free 'bdi->dev' to avoid use-after-free. > > But I am not sure if this solution will introduce new problems. So, I don't see why bdi->dev should be freed before bdi itself does. Would something like the following work? bdi_unregister() { ... if (bdi->dev) { ... device_get(bdi->dev); // to be put on release device_unregister(bdi->dev); } ... } release_bdi() { ... if (bdi->dev) { // warn if dev is still registered device_put(bdi->dev); } ... } Thanks. -- tejun