From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <stable-owner@vger.kernel.org>
Received: from mail.kernel.org ([198.145.29.99]:52356 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S2388464AbeGYDvU (ORCPT <rfc822;stable@vger.kernel.org>);
        Tue, 24 Jul 2018 23:51:20 -0400
Date: Tue, 24 Jul 2018 22:41:49 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, Shuah Khan <shuah@kernel.org>,
        Hiraku Toyooka <hiraku.toyooka@cybertrust.co.jp>,
        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: <20180724224149.0767fd13@gandalf.local.home>
In-Reply-To: <20180725101653.09e095092a4bb77e6fc558df@kernel.org>
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>
        <20180724173008.454cdf10@gandalf.local.home>
        <20180724191331.738eb819@gandalf.local.home>
        <20180725101653.09e095092a4bb77e6fc558df@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: stable-owner@vger.kernel.org
List-ID: <stable.vger.kernel.org>

On Wed, 25 Jul 2018 10:16:53 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Hm, as far as I can see, when register_trigger() returns >= 0, it already
> calls ->init the trigger_data. This means its refcount++, and in that
> case, below patch will miss to free the trigger_data.
> How about below for tentative fix?
> 
> 	if (!ret) {
> 		ret = -ENOENT;
> 		/* We have to forcibly free the trigger_data */
> 		goto out_free;
> 	} else if (ret > 0)
> 		ret = 0;

Or better yet, match it properly:

out_reg:
	/* Up the trigger_data count to make sure reg doesn't free it on failure */
	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) {
		cmd_ops->unreg(glob, trigger_ops, trigger_data, file);
		ret = -ENOENT;
	} else if (ret > 0)
		ret = 0;

	/* Down the counter of trigger_data or free it if not used anymore */
	event_trigger_free(trigger_ops, trigger_data);
 out:
	return ret;

-- Steve