Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755740AbYANXjI (ORCPT ); Mon, 14 Jan 2008 18:39:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752923AbYANXi4 (ORCPT ); Mon, 14 Jan 2008 18:38:56 -0500 Received: from e2.ny.us.ibm.com ([32.97.182.142]:54232 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752280AbYANXiy (ORCPT ); Mon, 14 Jan 2008 18:38:54 -0500 Date: Mon, 14 Jan 2008 17:39:10 -0600 From: "Serge E. Hallyn" To: Miklos Szeredi Cc: akpm@linux-foundation.org, hch@infradead.org, serue@us.ibm.com, viro@ftp.linux.org.uk, ebiederm@xmission.com, kzak@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, containers@lists.osdl.org, util-linux-ng@vger.kernel.org Subject: Re: [patch 9/9] unprivileged mounts: add "no submounts" flag Message-ID: <20080114233910.GI6704@sergelap.austin.ibm.com> References: <20080108113502.184459371@szeredi.hu> <20080108113634.382855604@szeredi.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080108113634.382855604@szeredi.hu> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3524 Lines: 89 Quoting Miklos Szeredi (miklos@szeredi.hu): > From: Miklos Szeredi > > Add a new mount flag "nomnt", which denies submounts for the owner. > This would be useful, if we want to support traditional /etc/fstab > based user mounts. > > In this case mount(8) would still have to be suid-root, to check the > mountpoint against the user/users flag in /etc/fstab, but /etc/mtab > would no longer be mandatory for storing the actual owner of the > mount. Ah, I see, so the floppy drive could be mounted as a MNT_NOMNT but MNT_USER mount with mnt_owner set. Makes sense. I'd ask for a better name than 'nomnt', but I can't think of one myself. > Signed-off-by: Miklos Szeredi Acked-by: Serge Hallyn > --- > > Index: linux/fs/namespace.c > =================================================================== > --- linux.orig/fs/namespace.c 2008-01-04 13:49:52.000000000 +0100 > +++ linux/fs/namespace.c 2008-01-04 13:50:28.000000000 +0100 > @@ -694,6 +694,7 @@ static int show_vfsmnt(struct seq_file * > { MNT_NOATIME, ",noatime" }, > { MNT_NODIRATIME, ",nodiratime" }, > { MNT_RELATIME, ",relatime" }, > + { MNT_NOMNT, ",nomnt" }, > { 0, NULL } > }; > struct proc_fs_info *fs_infop; > @@ -1044,6 +1045,9 @@ static bool permit_mount(struct nameidat > if (S_ISLNK(inode->i_mode)) > return false; > > + if (nd->path.mnt->mnt_flags & MNT_NOMNT) > + return false; > + > if (!is_mount_owner(nd->path.mnt, current->fsuid)) > return false; > > @@ -1888,9 +1892,11 @@ long do_mount(char *dev_name, char *dir_ > mnt_flags |= MNT_RELATIME; > if (flags & MS_RDONLY) > mnt_flags |= MNT_READONLY; > + if (flags & MS_NOMNT) > + mnt_flags |= MNT_NOMNT; > > - flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | > - MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT); > + flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_NOATIME | > + MS_NODIRATIME | MS_RELATIME | MS_KERNMOUNT | MS_NOMNT); > > /* ... and get the mountpoint */ > retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); > Index: linux/include/linux/fs.h > =================================================================== > --- linux.orig/include/linux/fs.h 2008-01-04 13:49:12.000000000 +0100 > +++ linux/include/linux/fs.h 2008-01-04 13:49:58.000000000 +0100 > @@ -130,6 +130,7 @@ extern int dir_notify_enable; > #define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */ > #define MS_I_VERSION (1<<23) /* Update inode I_version field */ > #define MS_SETUSER (1<<24) /* set mnt_uid to current user */ > +#define MS_NOMNT (1<<25) /* don't allow unprivileged submounts */ > #define MS_ACTIVE (1<<30) > #define MS_NOUSER (1<<31) > > Index: linux/include/linux/mount.h > =================================================================== > --- linux.orig/include/linux/mount.h 2008-01-04 13:45:45.000000000 +0100 > +++ linux/include/linux/mount.h 2008-01-04 13:49:58.000000000 +0100 > @@ -30,6 +30,7 @@ struct mnt_namespace; > #define MNT_NODIRATIME 0x10 > #define MNT_RELATIME 0x20 > #define MNT_READONLY 0x40 /* does the user want this to be r/o? */ > +#define MNT_NOMNT 0x80 > > #define MNT_SHRINKABLE 0x100 > #define MNT_IMBALANCED_WRITE_COUNT 0x200 /* just for debugging */ > > -- -- 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/