From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753856AbbFOGJ0 (ORCPT ); Mon, 15 Jun 2015 02:09:26 -0400 Received: from mail-wg0-f45.google.com ([74.125.82.45]:35374 "EHLO mail-wg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751386AbbFOGJV (ORCPT ); Mon, 15 Jun 2015 02:09:21 -0400 Message-ID: <557E6C0C.3050802@monom.org> Date: Mon, 15 Jun 2015 08:09:16 +0200 From: Daniel Wagner User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Hugh Dickins , Linus Torvalds CC: Prarit Bhargava , Morten Stevens , Dave Chinner , Eric Paris , Eric Sandeen , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: mm: shmem_zero_setup skip security check and lockdep conflict with XFS References: In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/14/2015 06:48 PM, Hugh Dickins wrote: > It appears that, at some point last year, XFS made directory handling > changes which bring it into lockdep conflict with shmem_zero_setup(): > it is surprising that mmap() can clone an inode while holding mmap_sem, > but that has been so for many years. > > Since those few lockdep traces that I've seen all implicated selinux, > I'm hoping that we can use the __shmem_file_setup(,,,S_PRIVATE) which > v3.13's commit c7277090927a ("security: shmem: implement kernel private > shmem inodes") introduced to avoid LSM checks on kernel-internal inodes: > the mmap("/dev/zero") cloned inode is indeed a kernel-internal detail. > > This also covers the !CONFIG_SHMEM use of ramfs to support /dev/zero > (and MAP_SHARED|MAP_ANONYMOUS). I thought there were also drivers > which cloned inode in mmap(), but if so, I cannot locate them now. > > Reported-and-tested-by: Prarit Bhargava > Reported-by: Daniel Wagner Reported-and-tested-by: Daniel Wagner Sorry for the long delay. It took me a while to figure out my original setup. I could verify that this patch made the lockdep message go away on 4.0-rc6 and also on 4.1-rc8. For the record: SELinux needs to be enabled triggering it. cheers, daniel