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 7623FC2BA2B for ; Thu, 16 Apr 2020 06:10:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5005B20771 for ; Thu, 16 Apr 2020 06:10:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZKpmVZh8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407720AbgDPGJ6 (ORCPT ); Thu, 16 Apr 2020 02:09:58 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:35848 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2407385AbgDPGJq (ORCPT ); Thu, 16 Apr 2020 02:09:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587017384; 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=WSD44ootEBXyzkzNcdpXGbzlmx+BBRKBSaXWnZtwryM=; b=ZKpmVZh8wM4HsQVjbYPbDw8hHARezeeWTbmghzTU52qvOGWQlUNTZDCBeyuGceqV3lXBqF qqpPE3ytSHHqRtTxeEPi2RRT9XfgSWRs/EicWkqmp9ubylJiAD78+/TabbZKxJn3HimU9M zDO4EMkmlL7VlXJ4vUke4GxsMppmn3Y= 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-8-KtHJpBBfOye0jlhWDKwoow-1; Thu, 16 Apr 2020 02:09:41 -0400 X-MC-Unique: KtHJpBBfOye0jlhWDKwoow-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id ECF3313F9; Thu, 16 Apr 2020 06:09:38 +0000 (UTC) Received: from T590 (ovpn-8-29.pek2.redhat.com [10.72.8.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B7C2699E03; Thu, 16 Apr 2020 06:09:26 +0000 (UTC) Date: Thu, 16 Apr 2020 14:09:21 +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: <20200416060921.GB2723777@T590> References: <20200414041902.16769-1-mcgrof@kernel.org> <20200414041902.16769-3-mcgrof@kernel.org> <20200416021036.GA2717677@T590> <20200416052524.GH11244@42.do-not-panic.com> <20200416054750.GA2723777@T590> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200416054750.GA2723777@T590> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 16, 2020 at 01:47:50PM +0800, Ming Lei wrote: > 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. Just test the 1st two patches via "blktrace /dev/sda2", follows the result, so this way can't be accepted. [root@ktest-01 ~]# blktrace /dev/sda2 Thread 0 failed open /sys/kernel/debug/block/sda2/trace0: 2/No such file or directory Thread 4 failed open /sys/kernel/debug/block/sda2/trace4: 2/No such file or directory Thread 1 failed open /sys/kernel/debug/block/sda2/trace1: 2/No such file or directory Thread 2 failed open /sys/kernel/debug/block/sda2/trace2: 2/No such file or directory Thread 5 failed open /sys/kernel/debug/block/sda2/trace5: 2/No such file or directory Thread 3 failed open /sys/kernel/debug/block/sda2/trace3: 2/No such file or directory Thread 6 failed open /sys/kernel/debug/block/sda2/trace6: 2/No such file or directory Thread 7 failed open /sys/kernel/debug/block/sda2/trace7: 2/No such file or directory FAILED to start thread on CPU 0: 1/Operation not permitted FAILED to start thread on CPU 1: 1/Operation not permitted FAILED to start thread on CPU 2: 1/Operation not permitted FAILED to start thread on CPU 3: 1/Operation not permitted FAILED to start thread on CPU 4: 1/Operation not permitted FAILED to start thread on CPU 5: 1/Operation not permitted FAILED to start thread on CPU 6: 1/Operation not permitted FAILED to start thread on CPU 7: 1/Operation not permitted Thanks, Ming