Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755966AbYANVxs (ORCPT ); Mon, 14 Jan 2008 16:53:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753076AbYANVxg (ORCPT ); Mon, 14 Jan 2008 16:53:36 -0500 Received: from e5.ny.us.ibm.com ([32.97.182.145]:60370 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752951AbYANVxd (ORCPT ); Mon, 14 Jan 2008 16:53:33 -0500 Date: Mon, 14 Jan 2008 15:53:51 -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 3/9] unprivileged mounts: account user mounts Message-ID: <20080114215351.GC6704@sergelap.austin.ibm.com> References: <20080108113502.184459371@szeredi.hu> <20080108113623.446872155@szeredi.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080108113623.446872155@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: 4867 Lines: 150 Quoting Miklos Szeredi (miklos@szeredi.hu): > From: Miklos Szeredi > > Add sysctl variables for accounting and limiting the number of user > mounts. > > The maximum number of user mounts is set to 1024 by default. This > won't in itself enable user mounts, setting a mount to be owned by a > user is first needed > > [akpm] > - don't use enumerated sysctls > > Signed-off-by: Miklos Szeredi Seems sane enough, given your responses to Dave. Acked-by: Serge Hallyn > --- > > Index: linux/Documentation/filesystems/proc.txt > =================================================================== > --- linux.orig/Documentation/filesystems/proc.txt 2008-01-03 17:12:58.000000000 +0100 > +++ linux/Documentation/filesystems/proc.txt 2008-01-03 21:15:35.000000000 +0100 > @@ -1012,6 +1012,15 @@ reaches aio-max-nr then io_setup will fa > raising aio-max-nr does not result in the pre-allocation or re-sizing > of any kernel data structures. > > +nr_user_mounts and max_user_mounts > +---------------------------------- > + > +These represent the number of "user" mounts and the maximum number of > +"user" mounts respectively. User mounts may be created by > +unprivileged users. User mounts may also be created with sysadmin > +privileges on behalf of a user, in which case nr_user_mounts may > +exceed max_user_mounts. > + > 2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats > ----------------------------------------------------------- > > Index: linux/fs/namespace.c > =================================================================== > --- linux.orig/fs/namespace.c 2008-01-03 21:14:16.000000000 +0100 > +++ linux/fs/namespace.c 2008-01-03 21:15:35.000000000 +0100 > @@ -44,6 +44,9 @@ static struct list_head *mount_hashtable > static struct kmem_cache *mnt_cache __read_mostly; > static struct rw_semaphore namespace_sem; > > +int nr_user_mounts; > +int max_user_mounts = 1024; > + > /* /sys/fs */ > struct kobject *fs_kobj; > EXPORT_SYMBOL_GPL(fs_kobj); > @@ -477,11 +480,30 @@ static struct vfsmount *skip_mnt_tree(st > return p; > } > > +static void dec_nr_user_mounts(void) > +{ > + spin_lock(&vfsmount_lock); > + nr_user_mounts--; > + spin_unlock(&vfsmount_lock); > +} > + > static void set_mnt_user(struct vfsmount *mnt) > { > BUG_ON(mnt->mnt_flags & MNT_USER); > mnt->mnt_uid = current->fsuid; > mnt->mnt_flags |= MNT_USER; > + spin_lock(&vfsmount_lock); > + nr_user_mounts++; > + spin_unlock(&vfsmount_lock); > +} > + > +static void clear_mnt_user(struct vfsmount *mnt) > +{ > + if (mnt->mnt_flags & MNT_USER) { > + mnt->mnt_uid = 0; > + mnt->mnt_flags &= ~MNT_USER; > + dec_nr_user_mounts(); > + } > } > > static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, > @@ -542,6 +564,7 @@ static inline void __mntput(struct vfsmo > */ > WARN_ON(atomic_read(&mnt->__mnt_writers)); > dput(mnt->mnt_root); > + clear_mnt_user(mnt); > free_vfsmnt(mnt); > deactivate_super(sb); > } > @@ -1306,6 +1329,7 @@ static int do_remount(struct nameidata * > else > err = do_remount_sb(sb, flags, data, 0); > if (!err) { > + clear_mnt_user(nd->path.mnt); > nd->path.mnt->mnt_flags = mnt_flags; > if (flags & MS_SETUSER) > set_mnt_user(nd->path.mnt); > Index: linux/include/linux/fs.h > =================================================================== > --- linux.orig/include/linux/fs.h 2008-01-03 20:52:38.000000000 +0100 > +++ linux/include/linux/fs.h 2008-01-03 21:15:35.000000000 +0100 > @@ -50,6 +50,9 @@ extern struct inodes_stat_t inodes_stat; > > extern int leases_enable, lease_break_time; > > +extern int nr_user_mounts; > +extern int max_user_mounts; > + > #ifdef CONFIG_DNOTIFY > extern int dir_notify_enable; > #endif > Index: linux/kernel/sysctl.c > =================================================================== > --- linux.orig/kernel/sysctl.c 2008-01-03 17:13:22.000000000 +0100 > +++ linux/kernel/sysctl.c 2008-01-03 21:15:35.000000000 +0100 > @@ -1288,6 +1288,22 @@ static struct ctl_table fs_table[] = { > #endif > #endif > { > + .ctl_name = CTL_UNNUMBERED, > + .procname = "nr_user_mounts", > + .data = &nr_user_mounts, > + .maxlen = sizeof(int), > + .mode = 0444, > + .proc_handler = &proc_dointvec, > + }, > + { > + .ctl_name = CTL_UNNUMBERED, > + .procname = "max_user_mounts", > + .data = &max_user_mounts, > + .maxlen = sizeof(int), > + .mode = 0644, > + .proc_handler = &proc_dointvec, > + }, > + { > .ctl_name = KERN_SETUID_DUMPABLE, > .procname = "suid_dumpable", > .data = &suid_dumpable, > > -- -- 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/