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 S1753333Ab3KDIu4 (ORCPT <rfc822;w@1wt.eu>);
	Mon, 4 Nov 2013 03:50:56 -0500
Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:47102 "EHLO
	LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751519Ab3KDIuy (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 4 Nov 2013 03:50:54 -0500
X-AuditID: 9c93016f-b7c3eae000004961-5c-52775fed546b
From: Namhyung Kim <namhyung@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, Namhyung Kim <namhyung.kim@lge.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Hyeoncheol Lee <cheol.lee@lge.com>,
        Hemant Kumar <hkshaw@linux.vnet.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        "zhangwei\(Jovi\)" <jovi.zhangwei@huawei.com>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Subject: Re: [PATCH 12/13] tracing/uprobes: Add more fetch functions
References: <1383029621-7384-1-git-send-email-namhyung@kernel.org>
	<1383029621-7384-13-git-send-email-namhyung@kernel.org>
	<20131031182218.GB11208@redhat.com>
Date: Mon, 04 Nov 2013 17:50:53 +0900
In-Reply-To: <20131031182218.GB11208@redhat.com> (Oleg Nesterov's message of
	"Thu, 31 Oct 2013 19:22:18 +0100")
Message-ID: <87k3go35zm.fsf@sejong.aot.lge.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
X-Brightmail-Tracker: AAAAAA==
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 31 Oct 2013 19:22:18 +0100, Oleg Nesterov wrote:
> On 10/29, Namhyung Kim wrote:
>>
>> +static void __user *get_user_vaddr(unsigned long addr, struct trace_uprobe *tu)
>> +{
>> +	unsigned long pgoff = addr >> PAGE_SHIFT;
>> +	struct vm_area_struct *vma;
>> +	struct address_space *mapping;
>> +	unsigned long vaddr = 0;
>> +
>> +	if (tu == NULL) {
>> +		/* A NULL tu means that we already got the vaddr */
>> +		return (void __force __user *) addr;
>> +	}
>> +
>> +	mapping = tu->inode->i_mapping;
>> +
>> +	mutex_lock(&mapping->i_mmap_mutex);
>> +	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
>> +		if (vma->vm_mm != current->mm)
>> +			continue;
>> +		if (!(vma->vm_flags & VM_READ))
>> +			continue;
>> +
>> +		vaddr = offset_to_vaddr(vma, addr);
>> +		break;
>> +	}
>> +	mutex_unlock(&mapping->i_mmap_mutex);
>> +
>> +	WARN_ON_ONCE(vaddr == 0);
>
> Hmm. But unless I missed something this "addr" passed as an argument can
> be wrong? And if nothing else this or another thread can unmap the vma?

You mean WARN_ON_ONCE here is superfluous?  I admit that it should
protect concurrent vma [un]mappings.  Please see my reply in other
thread for a new approach.

Thanks,
Namhyung