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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 DD30BC2BA2B for ; Thu, 16 Apr 2020 05:48:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD73021734 for ; Thu, 16 Apr 2020 05:48:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UYY6p4Pw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407189AbgDPFsY (ORCPT ); Thu, 16 Apr 2020 01:48:24 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:40335 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2407174AbgDPFsU (ORCPT ); Thu, 16 Apr 2020 01:48:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587016098; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Ae5ly7M/OETZeDnJohKJkBFZBczMSVWSQhC8QwiJPZs=; b=UYY6p4PwbvHlbEmYxBq7G9uPRiRA0vsLXFOe+sQgilHFf0khVS8zN/INJLzRXGgu0edg0i XZF8UXUIhV4E0TvUX4AE1eIR2chxhmUWYwlDlselmr5FnrEn9MxY3X5wDHeBRCnT3mU/vM b1fpWeYMIrsfv3ZzFXPEfxPk4fRbQSw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-97-y0juUd9SPm6Dr1B_bF4zJA-1; Thu, 16 Apr 2020 01:48:13 -0400 X-MC-Unique: y0juUd9SPm6Dr1B_bF4zJA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 09D7B801A09; Thu, 16 Apr 2020 05:48:11 +0000 (UTC) Received: from T590 (ovpn-8-29.pek2.redhat.com [10.72.8.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ED6405C1C5; Thu, 16 Apr 2020 05:47:55 +0000 (UTC) Date: Thu, 16 Apr 2020 13:47:50 +0800 From: Ming Lei To: Luis Chamberlain Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk, bvanassche@acm.org, gregkh@linuxfoundation.org, rostedt@goodmis.org, mingo@redhat.com, jack@suse.cz, nstange@suse.de, akpm@linux-foundation.org, mhocko@suse.com, yukuai3@huawei.com, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Omar Sandoval , Hannes Reinecke , Michal Hocko , syzbot+603294af2d01acfdd6da@syzkaller.appspotmail.com Subject: Re: [PATCH 2/5] blktrace: fix debugfs use after free Message-ID: <20200416054750.GA2723777@T590> References: <20200414041902.16769-1-mcgrof@kernel.org> <20200414041902.16769-3-mcgrof@kernel.org> <20200416021036.GA2717677@T590> <20200416052524.GH11244@42.do-not-panic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200416052524.GH11244@42.do-not-panic.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Apr 16, 2020 at 05:25:24AM +0000, Luis Chamberlain wrote: > On Thu, Apr 16, 2020 at 10:10:36AM +0800, Ming Lei wrote: > > In theory, multiple partitions can be traced concurrently, but looks > > it never works, so it won't cause trouble for multiple partition trace. > > > > One userspace visible change is that blktrace debugfs dir name is switched > > to disk name from partition name in case of partition trace, will it > > break some utilities? > > How is this possible, its not clear to me, we go from: > > - q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent), > - blk_debugfs_root); > > To this: > > + q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent), > + blk_debugfs_root); > > > Maybe I am overlooking something. Your patch removes the blktrace debugfs dir: do_blk_trace_setup() - dir = debugfs_lookup(buts->name, blk_debugfs_root); - if (!dir) - bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root); - Then create blktrace attributes under the dir of q->debugfs_dir. However, buts->name could be one partition device name, but q->debugfs_dir has to be disk name. This change is visible to blktrace utilities. Thanks, Ming