From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: Re: [PATCH review 6/6] userns: Allow the userns root to mount tmpfs. Date: Sun, 27 Jan 2013 18:23:34 +0000 Message-ID: <20130127182334.GC338@mail.hallyn.com> References: <87ehh8it9s.fsf@xmission.com> <87d2wshe6v.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux Containers , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Eric W. Biederman" Return-path: Content-Disposition: inline In-Reply-To: <87d2wshe6v.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org): > > 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" Acked-by: Serge Hallyn > --- > 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) > -- > 1.7.5.4