From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by kanga.kvack.org (Postfix) with ESMTP id 164A56B006C for ; Mon, 15 Jun 2015 02:09:22 -0400 (EDT) Received: by wgbhy7 with SMTP id hy7so26785376wgb.2 for ; Sun, 14 Jun 2015 23:09:21 -0700 (PDT) Received: from mail-wi0-x229.google.com (mail-wi0-x229.google.com. [2a00:1450:400c:c05::229]) by mx.google.com with ESMTPS id f8si16592587wiy.57.2015.06.14.23.09.20 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 14 Jun 2015 23:09:20 -0700 (PDT) Received: by wiga1 with SMTP id a1so65946844wig.0 for ; Sun, 14 Jun 2015 23:09:19 -0700 (PDT) Message-ID: <557E6C0C.3050802@monom.org> Date: Mon, 15 Jun 2015 08:09:16 +0200 From: Daniel Wagner MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org