Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756548AbbFQLpi (ORCPT ); Wed, 17 Jun 2015 07:45:38 -0400 Received: from mx01.imt-systems.com ([212.224.83.170]:42579 "EHLO mx01.imt-systems.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753470AbbFQLpb (ORCPT ); Wed, 17 Jun 2015 07:45:31 -0400 MIME-Version: 1.0 In-Reply-To: <557E6C0C.3050802@monom.org> References: <557E6C0C.3050802@monom.org> Date: Wed, 17 Jun 2015 13:45:27 +0200 Message-ID: Subject: Re: mm: shmem_zero_setup skip security check and lockdep conflict with XFS From: Morten Stevens To: Daniel Wagner Cc: Hugh Dickins , Linus Torvalds , Prarit Bhargava , Morten Stevens , Dave Chinner , Eric Paris , Eric Sandeen , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 X-Spam-Score: 0 () Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1643 Lines: 36 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. Best regards, Morten -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/