From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gao feng Subject: Re: [PATCH review 6/6] userns: Allow the userns root to mount tmpfs. Date: Mon, 28 Jan 2013 09:28:03 +0800 Message-ID: <5105D423.9080909@cn.fujitsu.com> References: <87ehh8it9s.fsf@xmission.com> <87d2wshe6v.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: Linux Containers , "Serge E. Hallyn" , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: "Eric W. Biederman" Return-path: Received: from cn.fujitsu.com ([222.73.24.84]:3667 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1755670Ab3A1B1d (ORCPT ); Sun, 27 Jan 2013 20:27:33 -0500 In-Reply-To: <87d2wshe6v.fsf@xmission.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 2013/01/26 10:26, Eric W. Biederman wrote: > > There is no backing store to tmpfs and file creation rules are the > same as for any other filesystem so it is semantically safe to allow > unprivileged users to mount it. ramfs is safe for the same reasons so > allow either flavor of tmpfs to be mounted by a user namespace root > user. > > The memory control group successfully limits how much memory tmpfs can > consume on any system that cares about a user namespace root using > tmpfs to exhaust memory the memory control group can be deployed. > > Signed-off-by: "Eric W. Biederman" > --- useful to me,thanks Eric & Serge. Acked-by: Gao feng > mm/shmem.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 5c90d84..197ca5e 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2766,6 +2766,7 @@ static struct file_system_type shmem_fs_type = { > .name = "tmpfs", > .mount = shmem_mount, > .kill_sb = kill_litter_super, > + .fs_flags = FS_USERNS_MOUNT, > }; > > int __init shmem_init(void) > @@ -2823,6 +2824,7 @@ static struct file_system_type shmem_fs_type = { > .name = "tmpfs", > .mount = ramfs_mount, > .kill_sb = kill_litter_super, > + .fs_flags = FS_USERNS_MOUNT, > }; > > int __init shmem_init(void) >