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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,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 562B8C28CF6 for ; Wed, 25 Jul 2018 01:05:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0EDB620852 for ; Wed, 25 Jul 2018 01:05:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="bvAE6qXz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0EDB620852 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388547AbeGYCOb (ORCPT ); Tue, 24 Jul 2018 22:14:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:38244 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388517AbeGYCOb (ORCPT ); Tue, 24 Jul 2018 22:14:31 -0400 Received: from devbox (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 844DC20852; Wed, 25 Jul 2018 01:05:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1532480723; bh=MkutZ6Iq8zkXBC7KWbtN0iE3PYyZlTFpgq4rLA6FFUg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=bvAE6qXzpJ2fww/h2nd5ayaya9eDN6AXXVfCYnC9dqjEbPZWPodPOnFbOcwJbqlvv BxKFycfM7aOinp6Y47x4Etj+Cg0MbG+9KXtCu8NjIOuEZADBD0Hpl4KQq7TLsZ5PaC mrNyWYp1NX7Ehe5NlfuNBfZxZhCdd5DhB85jH6ZI= Date: Wed, 25 Jul 2018 10:05:20 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Ingo Molnar , Shuah Khan , Tom Zanussi , Hiraku Toyooka , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/3] [BUGFIX] tracing: Fix double free of event_trigger_data Message-Id: <20180725100520.9370df20d29d529236f4a368@kernel.org> In-Reply-To: <20180724164959.3cbc1422@gandalf.local.home> References: <153149923649.11274.14970833360963898112.stgit@devbox> <153149926702.11274.12489440326560729788.stgit@devbox> <20180723221006.60cc7aa9@vmware.local.home> <20180725000909.6c8b2f3881ee75c4f6bd466b@kernel.org> <20180724164959.3cbc1422@gandalf.local.home> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 24 Jul 2018 16:49:59 -0400 Steven Rostedt wrote: > On Wed, 25 Jul 2018 00:09:09 +0900 > Masami Hiramatsu wrote: > > > Hmm, your patch seems to leak a memory since event_trigger_init() will > > be called twice on same trigger_data (Note that event_trigger_init() > > does not init ref counter, but increment it.) So we should decrement > > it when we find it is succeeded. Moreover, if register_trigger() > > Good catch, and easily fixed. > > > fails before calling data->ops->init() (see -EEXIST case), the ref > > counter will be 0 (-1 +1). But if it fails after data->ops->init(), > > the ref counter will be 1 (-1 +1 +1). It still be unstable. > > (Ah, that means we may have another trouble...) > > I'm not sure there's a problem here. I now have: > > out_reg: > /* Up the trigger_data count to make sure reg doesn't free it on failuer */ > event_trigger_init(trigger_ops, trigger_data); > ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file); > /* > * The above returns on success the # of functions enabled, > * but if it didn't find any functions it returns zero. > * Consider no functions a failure too. > */ > if (!ret) { > ret = -ENOENT; > } else if (ret > 0) > ret = 0; Can we mixed up ret == 0 and ret > 0? It seems cmd_ops->reg() == 0 is a failure case. > > /* Down the counter of trigger_data or free it if not used anymore */ > event_trigger_free(trigger_ops, trigger_data); > out: > return ret; > > Thus we increment trigger_data before calling reg, and free it > afterward. But if reg() did an init too, then the event_trigger_free() > just decs the ref counter. To avoid confusion, I would like to suggest to rename those pair to event_trigger_data_get/put(). :) > > As for register_trigger() > > > > > > > > > > P.S. This brings up another minor bug. The failure should return ENOMEM > > > not ENOENT. > > > > Hmm it seems we should review the register_trigger() implementation. > > It should return the return value of trace_event_trigger_enable_disable(), > > shouldn't it? > > > > Yeah, that's not done well. I'll fix it up. Thanks! > > Thanks for pointing it out. > > -- Steve -- Masami Hiramatsu