From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752727AbbFRAW7 (ORCPT ); Wed, 17 Jun 2015 20:22:59 -0400 Received: from mail-ig0-f169.google.com ([209.85.213.169]:35928 "EHLO mail-ig0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751193AbbFRAWv (ORCPT ); Wed, 17 Jun 2015 20:22:51 -0400 MIME-Version: 1.0 In-Reply-To: References: <557E6C0C.3050802@monom.org> Date: Thu, 18 Jun 2015 01:22:50 +0100 Message-ID: Subject: Re: mm: shmem_zero_setup skip security check and lockdep conflict with XFS From: Hugh Dickins To: Morten Stevens Cc: Daniel Wagner , Linus Torvalds , Prarit Bhargava , Dave Chinner , Eric Paris , Eric Sandeen , Andrew Morton , linux-mm , linux-kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Wed, Jun 17, 2015 at 12:45 PM, Morten Stevens wrote: > 2015-06-15 8:09 GMT+02:00 Daniel Wagner : >> 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. > > Yes, it's also fixed for me after applying this patch to 4.1-rc8. Thank you - Hugh > > Best regards, > > Morten