From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f176.google.com (mail-ig0-f176.google.com [209.85.213.176]) by kanga.kvack.org (Postfix) with ESMTP id C93696B0074 for ; Wed, 17 Jun 2015 20:22:51 -0400 (EDT) Received: by igbqq3 with SMTP id qq3so3066979igb.0 for ; Wed, 17 Jun 2015 17:22:51 -0700 (PDT) Received: from mail-ie0-x22b.google.com (mail-ie0-x22b.google.com. [2607:f8b0:4001:c03::22b]) by mx.google.com with ESMTPS id 2si5181181igt.56.2015.06.17.17.22.51 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Jun 2015 17:22:51 -0700 (PDT) Received: by iecrd14 with SMTP id rd14so44879679iec.3 for ; Wed, 17 Jun 2015 17:22:51 -0700 (PDT) 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 Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Morten Stevens Cc: Daniel Wagner , Linus Torvalds , Prarit Bhargava , Dave Chinner , Eric Paris , Eric Sandeen , Andrew Morton , linux-mm , linux-kernel 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 -- 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