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From: Miklos Szeredi <miklos@szeredi.hu>
To: akpm@linux-foundation.org, serue@us.ibm.com,
	viro@ftp.linux.org.uk, linuxram@us.ibm.com,
	ebiederm@xmission.com, kzak@redhat.com
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	containers@lists.osdl.org
Subject: [patch 03/10] unprivileged mounts: account user mounts
Date: Fri, 27 Apr 2007 14:04:20 +0200	[thread overview]
Message-ID: <20070427120531.054028653@szeredi.hu> (raw)
In-Reply-To: <20070427120417.110164241@szeredi.hu>

[-- Attachment #1: unprivileged-mounts-account-user-mounts.patch --]
[-- Type: text/plain, Size: 4208 bytes --]

From: Miklos Szeredi <mszeredi@suse.cz>

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 <mszeredi@suse.cz>
---

Index: linux/Documentation/filesystems/proc.txt
===================================================================
--- linux.orig/Documentation/filesystems/proc.txt	2007-04-26 13:08:35.000000000 +0200
+++ linux/Documentation/filesystems/proc.txt	2007-04-26 13:17:13.000000000 +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	2007-04-26 13:16:21.000000000 +0200
+++ linux/fs/namespace.c	2007-04-26 13:17:13.000000000 +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->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,
@@ -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);
 }
@@ -1028,6 +1051,7 @@ 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	2007-04-26 13:08:36.000000000 +0200
+++ linux/include/linux/fs.h	2007-04-26 13:17:13.000000000 +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
Index: linux/kernel/sysctl.c
===================================================================
--- linux.orig/kernel/sysctl.c	2007-04-26 13:08:35.000000000 +0200
+++ linux/kernel/sysctl.c	2007-04-26 13:17:13.000000000 +0200
@@ -1064,6 +1064,22 @@ static 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,

--

  parent reply	other threads:[~2007-04-27 12:08 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-04-27 12:04 [patch 00/10] mount ownership and unprivileged mount syscall (v5) Miklos Szeredi
2007-04-27 12:04 ` [patch 01/10] unprivileged mounts: add user mounts to the kernel Miklos Szeredi
2007-04-27 12:04 ` [patch 02/10] unprivileged mounts: allow unprivileged umount Miklos Szeredi
2007-04-27 12:04 ` Miklos Szeredi [this message]
2007-04-27 12:04 ` [patch 04/10] unprivileged mounts: propagate error values from clone_mnt Miklos Szeredi
2007-04-27 12:04 ` [patch 05/10] unprivileged mounts: allow unprivileged bind mounts Miklos Szeredi
2007-04-27 12:04 ` [patch 06/10] unprivileged mounts: put declaration of put_filesystem() in fs.h Miklos Szeredi
2007-04-27 12:04 ` [patch 07/10] unprivileged mounts: allow unprivileged mounts Miklos Szeredi
2007-04-27 12:04 ` [patch 08/10] unprivileged mounts: allow unprivileged fuse mounts Miklos Szeredi
2007-04-27 12:04 ` [patch 09/10] unprivileged mounts: propagation: inherit owner from parent Miklos Szeredi
2007-04-27 12:04 ` [patch 10/10] unprivileged mounts: add "no submounts" flag Miklos Szeredi

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