From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754548AbXDUNjE (ORCPT ); Sat, 21 Apr 2007 09:39:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754546AbXDUNjE (ORCPT ); Sat, 21 Apr 2007 09:39:04 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:58121 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754545AbXDUNjB (ORCPT ); Sat, 21 Apr 2007 09:39:01 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Miklos Szeredi Cc: akpm@linux-foundation.org, serue@us.ibm.com, viro@ftp.linux.org.uk, linuxram@us.ibm.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, containers@lists.osdl.org Subject: Re: [patch 3/8] account user mounts References: <20070420102532.385211890@szeredi.hu> <20070420102631.544911966@szeredi.hu> Date: Sat, 21 Apr 2007 07:37:21 -0600 In-Reply-To: <20070420102631.544911966@szeredi.hu> (Miklos Szeredi's message of "Fri, 20 Apr 2007 12:25:35 +0200") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Miklos Szeredi writes: > 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 Since each mount has a user can we just make this a per user rlimit? If we are going to implement a sysctl at this point I think it should be a global limit that doesn't care if who you are. Even root can have recursive mounts that attempt to get out of control. Also currently you are not checking the max_users. It looks like you do this in a later patch but still it is a little strange to allow user own mounts and have accounting but to not check the limit at this state. Eric > > Signed-off-by: Miklos Szeredi > --- > > Index: linux/include/linux/sysctl.h > =================================================================== > --- linux.orig/include/linux/sysctl.h 2007-04-20 11:55:02.000000000 +0200 > +++ linux/include/linux/sysctl.h 2007-04-20 11:55:07.000000000 +0200 > @@ -818,6 +818,8 @@ enum > FS_AIO_NR=18, /* current system-wide number of aio requests */ > FS_AIO_MAX_NR=19, /* system-wide maximum number of aio requests */ > FS_INOTIFY=20, /* inotify submenu */ > + FS_NR_USER_MOUNTS=21, /* int:current number of user mounts */ > + FS_MAX_USER_MOUNTS=22, /* int:maximum number of user mounts */ > FS_OCFS2=988, /* ocfs2 */ > }; > > Index: linux/kernel/sysctl.c > =================================================================== > --- linux.orig/kernel/sysctl.c 2007-04-20 11:55:02.000000000 +0200 > +++ linux/kernel/sysctl.c 2007-04-20 11:55:07.000000000 +0200 > @@ -1063,6 +1063,22 @@ static ctl_table fs_table[] = { > #endif > #endif > { > + .ctl_name = FS_NR_USER_MOUNTS, > + .procname = "nr_user_mounts", > + .data = &nr_user_mounts, > + .maxlen = sizeof(int), > + .mode = 0444, > + .proc_handler = &proc_dointvec, > + }, > + { > + .ctl_name = FS_MAX_USER_MOUNTS, > + .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, > Index: linux/Documentation/filesystems/proc.txt > =================================================================== > --- linux.orig/Documentation/filesystems/proc.txt 2007-04-20 11:55:02.000000000 > +0200 > +++ linux/Documentation/filesystems/proc.txt 2007-04-20 11:55:07.000000000 +0200 > @@ -923,6 +923,15 @@ 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 2007-04-20 11:55:06.000000000 +0200 > +++ linux/fs/namespace.c 2007-04-20 11:55:07.000000000 +0200 > @@ -39,6 +39,9 @@ static int hash_mask __read_mostly, hash > 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 */ > decl_subsys(fs, NULL, NULL); > EXPORT_SYMBOL_GPL(fs_subsys); > @@ -227,11 +230,30 @@ 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->uid; > 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, > @@ -283,6 +305,7 @@ static inline void __mntput(struct vfsmo > { > struct super_block *sb = mnt->mnt_sb; > dput(mnt->mnt_root); > + clear_mnt_user(mnt); > free_vfsmnt(mnt); > deactivate_super(sb); > } > @@ -1023,6 +1046,7 @@ static int do_remount(struct nameidata * > down_write(&sb->s_umount); > err = do_remount_sb(sb, flags, data, 0); > if (!err) { > + clear_mnt_user(nd->mnt); > nd->mnt->mnt_flags = mnt_flags; > if (flags & MS_SETUSER) > set_mnt_user(nd->mnt); > Index: linux/include/linux/fs.h > =================================================================== > --- linux.orig/include/linux/fs.h 2007-04-20 11:55:05.000000000 +0200 > +++ linux/include/linux/fs.h 2007-04-20 11:55:07.000000000 +0200 > @@ -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 > > --