From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751821AbdJZGVe (ORCPT <rfc822;w@1wt.eu>);
        Thu, 26 Oct 2017 02:21:34 -0400
Received: from mail.kernel.org ([198.145.29.99]:48840 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751651AbdJZGVd (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 26 Oct 2017 02:21:33 -0400
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65B96218B5
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org
Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mhiramat@kernel.org
Date: Thu, 26 Oct 2017 15:21:30 +0900
From: Masami Hiramatsu <mhiramat@kernel.org>
To: chenjiankang <chenjiankang1@huawei.com>
Cc: <ananth@linux.vnet.ibm.com>, <anil.s.keshavamurthy@intel.com>,
        <linux-kernel@vger.kernel.org>, <xieyisheng1@huawei.com>,
        <wangkefeng.wang@huawei.com>, <davem@davemloft.net>
Subject: Re: [PATCH] kernel/kprobes: add check to avoid kprobe memory leak
Message-Id: <20171026152130.119473592483b3106b2ac4df@kernel.org>
In-Reply-To: <a11a31b6-bff3-b6c1-db47-787540cd0d07@huawei.com>
References: <1508847422-63641-1-git-send-email-chenjiankang1@huawei.com>
        <20171026015453.ba08699319ffaa9a18bbd8e3@kernel.org>
        <a11a31b6-bff3-b6c1-db47-787540cd0d07@huawei.com>
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
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 26 Oct 2017 09:22:23 +0800
chenjiankang <chenjiankang1@huawei.com> wrote:

> > On Tue, 24 Oct 2017 20:17:02 +0800
> > JianKang Chen <chenjiankang1@huawei.com> wrote:
> > 
> >> The function register_kretprobe is used to initialize a struct
> >> kretprobe and allocate a list table for kprobe instance.
> >> However,in this function, there is a memory leak.
> >>
> >> The test case:
> >>
> >> static struct kretprobe rp;
> >> struct  kretprobe *rps[10]={&rp ,&rp ,&rp ,
> >> &rp ,&rp ,&rp ,&rp ,&rp ,&rp,&rp};
> > 
> > What ? this is buggy code. you must not list same kretprobe.
> > But, year, since register_kprobe() already has similar protection against
> > reusing, register_kretprobe() should do so.
> > 
> > [..]
> >>  	raw_spin_lock_init(&rp->lock);
> >> +
> >> +	if (!hlist_empty(&rp->free_instances))
> >> +		return -EBUSY;
> >> +
> > 
> > Hmm, but can you use check_kprobe_rereg() before raw_spin_lock_init()?
> > If user reuses rp after it starts, rp->lock can already be used.
> 
> Hmm, your advice is very good, we can use check_kprobe_rereg() at 
> the beginning of the register_kretprobe();
> 
> For example:
> 
> int register_kretprobe(struct kretprobe *rp)
> {
>         int ret = 0;
>         struct kretprobe_instance *inst;
>         int i;
>         void *addr;
> 
>         ret = check_kprobe_rereg(&rp->kp);
>         if (ret)
>                 return ret;

Yeah, this looks much better for me :)

Thanks,

> 
> Thank you!
>  
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>