[PATCH 1/3] user namespaces: introduce user_struct->user_namespace relationship

[PATCH 1/3] user namespaces: introduce user_struct->user_namespace relationship

[Serge E. Hallyn]

Here's just a repost given some of the feedback from the last round.

Question: do we really want a patch renaming kernel/user_namespace.c,
include/linux/user_namespace.c, and struct user_namespace all to
user_ns?  I'm fine with it if we are, but it'll be a pretty big 
patch with no other effect.

-serge

From aa31de8d2e62d1903f8dfaa97e71cca7560632ce Mon Sep 17 00:00:00 2001
From: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Date: Tue, 22 Jul 2008 13:31:37 -0500
Subject: [PATCH 1/3] user namespaces: introduce user_struct->user_namespace relationship

When a task does clone(CLONE_NEWNS), the task's user is the 'creator' of the
new user_namespace, and the user_namespace is tacked onto a list of those
created by this user.

Changelog:
	Aug 1: renamed user->user_namespace to user_ns, as the next
		patch did anyway.
	Aug 1: move put_user_ns call in one free_user() definition
		to move it outside the lock in free_user.  put_user_ns
		calls free_user on the user_ns->creator, which in
		turn would grab the lock again.

Signed-off-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 include/linux/sched.h          |    1 +
 include/linux/user_namespace.h |    1 +
 kernel/user.c                  |    7 +++++++
 kernel/user_namespace.c        |   20 +++++++++++---------
 4 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5270d44..0149e77 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -600,6 +600,7 @@ struct user_struct {
 	/* Hash table maintenance information */
 	struct hlist_node uidhash_node;
 	uid_t uid;
+	struct user_namespace *user_ns;
 
 #ifdef CONFIG_USER_SCHED
 	struct task_group *tg;
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index b5f41d4..f9477c3 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -13,6 +13,7 @@ struct user_namespace {
 	struct kref		kref;
 	struct hlist_head	uidhash_table[UIDHASH_SZ];
 	struct user_struct	*root_user;
+	struct user_struct	*creator;
 };
 
 extern struct user_namespace init_user_ns;
diff --git a/kernel/user.c b/kernel/user.c
index 865ecf5..aedb3a1 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -22,6 +22,7 @@ struct user_namespace init_user_ns = {
 		.refcount	= ATOMIC_INIT(2),
 	},
 	.root_user = &root_user,
+	.creator = &root_user,
 };
 EXPORT_SYMBOL_GPL(init_user_ns);
 
@@ -53,6 +54,7 @@ struct user_struct root_user = {
 	.files		= ATOMIC_INIT(0),
 	.sigpending	= ATOMIC_INIT(0),
 	.locked_shm     = 0,
+	.user_ns	= &init_user_ns,
 #ifdef CONFIG_USER_SCHED
 	.tg		= &init_task_group,
 #endif
@@ -325,6 +327,7 @@ static inline void free_user(struct user_struct *up, unsigned long flags)
 	atomic_inc(&up->__count);
 	spin_unlock_irqrestore(&uidhash_lock, flags);
 
+	put_user_ns(up->user_ns);
 	INIT_WORK(&up->work, remove_user_sysfs_dir);
 	schedule_work(&up->work);
 }
@@ -347,6 +350,7 @@ static inline void free_user(struct user_struct *up, unsigned long flags)
 	sched_destroy_user(up);
 	key_put(up->uid_keyring);
 	key_put(up->session_keyring);
+	put_user_ns(up->user_ns);
 	kmem_cache_free(uid_cachep, up);
 }
 
@@ -409,6 +413,8 @@ struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
 		if (sched_create_user(new) < 0)
 			goto out_free_user;
 
+		new->user_ns = get_user_ns(ns);
+
 		if (uids_user_create(new))
 			goto out_destoy_sched;
 
@@ -441,6 +447,7 @@ struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
 
 out_destoy_sched:
 	sched_destroy_user(new);
+	put_user_ns(new->user_ns);
 out_free_user:
 	kmem_cache_free(uid_cachep, new);
 out_unlock:
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index a9ab059..e8db443 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -19,7 +19,6 @@
 static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 {
 	struct user_namespace *ns;
-	struct user_struct *new_user;
 	int n;
 
 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
@@ -38,15 +37,17 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 		return ERR_PTR(-ENOMEM);
 	}
 
-	/* Reset current->user with a new one */
-	new_user = alloc_uid(ns, current->uid);
-	if (!new_user) {
-		free_uid(ns->root_user);
-		kfree(ns);
-		return ERR_PTR(-ENOMEM);
-	}
+	/* pin the creating user */
+	ns->creator = current->user;
+	atomic_inc(&ns->creator->__count);
+
+	/*
+	 * The alloc_uid() incremented the userns refcount,
+	 * so drop it again 
+	 */
+	put_user_ns(ns);
 
-	switch_uid(new_user);
+	switch_uid(ns->root_user);
 	return ns;
 }
 
@@ -72,6 +73,7 @@ void free_user_ns(struct kref *kref)
 
 	ns = container_of(kref, struct user_namespace, kref);
 	release_uids(ns);
+	free_uid(ns->creator);
 	kfree(ns);
 }
 EXPORT_SYMBOL(free_user_ns);
-- 
1.5.4.3

[PATCH 2/3] user namespaces: move user_ns from nsproxy into user struct

[Serge E. Hallyn]

When we get the sysfs support needed to support fair user scheduling
along with user namespaces, then we will need to be able to get the
user namespace from the user struct.

So we need the user_ns to be a part of struct user.  Once we can
access it from tsk->user, we no longer have a use for
tsk->nsproxy->user_ns.

When a user_namespace is created, the user which created it is
marked as its 'creator'.  The user_namespace pins the creator.
Each userid in a user_ns pins the user_ns.  This keeps refcounting
nice and simple.

At the same time, this patch simplifies the refcounting.  The current
user and userns locking works as follows:

	The task pins the user struct.

	The task pins the nsproxy, the nsproxy pins the user_ns.

	When a new user_ns is created, it creates a root user for
	it, and pins it.  When the nsproxy releases the user_ns,
	the userns tries to release all its user structs.

	So you see that the refcounting "works" for now, but only
	because the nsproxy (and therefore usr_ns) and user structs
	will be freed at the same time - when the last task using
	them is released.

	Now we need to put the user_ns in the struct user.  You can
	see that will mess up the refcounting.

	Fortunately, once the user_ns is available from tsk->user,
	we don't need it in nsproxy.

	So here is how the refcounting *should* be done:

	The task pins the user struct.

	The user struct pins its user namespace.

	The user namespace pins the struct user which created it.

	A user namespace now doesn't need to release its userids,
	because it is only released when its last user disappears.

This patch makes those changes.

Signed-off-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 include/linux/init_task.h      |    1 -
 include/linux/key.h            |    3 ++
 include/linux/nsproxy.h        |    1 -
 include/linux/sched.h          |    1 +
 include/linux/user_namespace.h |   10 +++-----
 kernel/fork.c                  |    3 +-
 kernel/nsproxy.c               |   10 +-------
 kernel/sys.c                   |    4 +-
 kernel/user.c                  |   42 +++++++++------------------------------
 kernel/user_namespace.c        |   36 +++++++++------------------------
 security/keys/process_keys.c   |    7 +++++-
 11 files changed, 39 insertions(+), 79 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 021d8e7..550058b 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -57,7 +57,6 @@ extern struct nsproxy init_nsproxy;
 	.mnt_ns		= NULL,						\
 	INIT_NET_NS(net_ns)                                             \
 	INIT_IPC_NS(ipc_ns)						\
-	.user_ns	= &init_user_ns,				\
 }
 
 #define INIT_SIGHAND(sighand) {						\
diff --git a/include/linux/key.h b/include/linux/key.h
index c45c962..ba53aef 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -277,6 +277,8 @@ extern ctl_table key_sysctls[];
  * the userspace interface
  */
 extern void switch_uid_keyring(struct user_struct *new_user);
+extern void switch_uid_keyring_task(struct task_struct *tsk,
+				struct user_struct *new_user);
 extern int copy_keys(unsigned long clone_flags, struct task_struct *tsk);
 extern int copy_thread_group_keys(struct task_struct *tsk);
 extern void exit_keys(struct task_struct *tsk);
@@ -305,6 +307,7 @@ extern void key_init(void);
 #define key_ref_to_ptr(k)		({ NULL; })
 #define is_key_possessed(k)		0
 #define switch_uid_keyring(u)		do { } while(0)
+#define switch_uid_keyring_task(t,u)	do { } while(0)
 #define __install_session_keyring(t, k)	({ NULL; })
 #define copy_keys(f,t)			0
 #define copy_thread_group_keys(t)	0
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index c8a768e..afad7de 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -27,7 +27,6 @@ struct nsproxy {
 	struct ipc_namespace *ipc_ns;
 	struct mnt_namespace *mnt_ns;
 	struct pid_namespace *pid_ns;
-	struct user_namespace *user_ns;
 	struct net 	     *net_ns;
 };
 extern struct nsproxy init_nsproxy;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0149e77..daacdb7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1738,6 +1738,7 @@ static inline struct user_struct *get_uid(struct user_struct *u)
 }
 extern void free_uid(struct user_struct *);
 extern void switch_uid(struct user_struct *);
+extern void task_switch_uid(struct task_struct *tsk, struct user_struct *);
 extern void release_uids(struct user_namespace *ns);
 
 #include <asm/current.h>
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index f9477c3..1b4959d 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -27,8 +27,7 @@ static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
 	return ns;
 }
 
-extern struct user_namespace *copy_user_ns(int flags,
-					   struct user_namespace *old_ns);
+extern int create_new_userns(int flags, struct task_struct *tsk);
 extern void free_user_ns(struct kref *kref);
 
 static inline void put_user_ns(struct user_namespace *ns)
@@ -44,13 +43,12 @@ static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
 	return &init_user_ns;
 }
 
-static inline struct user_namespace *copy_user_ns(int flags,
-						  struct user_namespace *old_ns)
+static inline int create_new_userns(int flags, struct task_struct *tsk)
 {
 	if (flags & CLONE_NEWUSER)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
-	return old_ns;
+	return 0;
 }
 
 static inline void put_user_ns(struct user_namespace *ns)
diff --git a/kernel/fork.c b/kernel/fork.c
index 7ce2ebe..b5d4dc5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -941,8 +941,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	retval = -EAGAIN;
 	if (atomic_read(&p->user->processes) >=
 			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
-		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
-		    p->user != current->nsproxy->user_ns->root_user)
+		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE))
 			goto bad_fork_free;
 	}
 
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 21575fc..2edac05 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -81,11 +81,9 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
 		goto out_pid;
 	}
 
-	new_nsp->user_ns = copy_user_ns(flags, tsk->nsproxy->user_ns);
-	if (IS_ERR(new_nsp->user_ns)) {
-		err = PTR_ERR(new_nsp->user_ns);
+	err = create_new_userns(flags, tsk);
+	if (err)
 		goto out_user;
-	}
 
 	new_nsp->net_ns = copy_net_ns(flags, tsk->nsproxy->net_ns);
 	if (IS_ERR(new_nsp->net_ns)) {
@@ -96,8 +94,6 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
 	return new_nsp;
 
 out_net:
-	if (new_nsp->user_ns)
-		put_user_ns(new_nsp->user_ns);
 out_user:
 	if (new_nsp->pid_ns)
 		put_pid_ns(new_nsp->pid_ns);
@@ -174,8 +170,6 @@ void free_nsproxy(struct nsproxy *ns)
 		put_ipc_ns(ns->ipc_ns);
 	if (ns->pid_ns)
 		put_pid_ns(ns->pid_ns);
-	if (ns->user_ns)
-		put_user_ns(ns->user_ns);
 	put_net(ns->net_ns);
 	kmem_cache_free(nsproxy_cachep, ns);
 }
diff --git a/kernel/sys.c b/kernel/sys.c
index c018580..4d8d415 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -553,13 +553,13 @@ static int set_user(uid_t new_ruid, int dumpclear)
 {
 	struct user_struct *new_user;
 
-	new_user = alloc_uid(current->nsproxy->user_ns, new_ruid);
+	new_user = alloc_uid(current->user->user_ns, new_ruid);
 	if (!new_user)
 		return -EAGAIN;
 
 	if (atomic_read(&new_user->processes) >=
 				current->signal->rlim[RLIMIT_NPROC].rlim_cur &&
-			new_user != current->nsproxy->user_ns->root_user) {
+			!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
 		free_uid(new_user);
 		return -EAGAIN;
 	}
diff --git a/kernel/user.c b/kernel/user.c
index aedb3a1..d3dd353 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -366,7 +366,7 @@ struct user_struct *find_user(uid_t uid)
 {
 	struct user_struct *ret;
 	unsigned long flags;
-	struct user_namespace *ns = current->nsproxy->user_ns;
+	struct user_namespace *ns = current->user->user_ns;
 
 	spin_lock_irqsave(&uidhash_lock, flags);
 	ret = uid_hash_find(uid, uidhashentry(ns, uid));
@@ -455,7 +455,7 @@ out_unlock:
 	return NULL;
 }
 
-void switch_uid(struct user_struct *new_user)
+void task_switch_uid(struct task_struct *tsk, struct user_struct *new_user)
 {
 	struct user_struct *old_user;
 
@@ -464,12 +464,12 @@ void switch_uid(struct user_struct *new_user)
 	 * cheaply with the new uid cache, so if it matters
 	 * we should be checking for it.  -DaveM
 	 */
-	old_user = current->user;
+	old_user = tsk->user;
 	atomic_inc(&new_user->processes);
 	atomic_dec(&old_user->processes);
-	switch_uid_keyring(new_user);
-	current->user = new_user;
-	sched_switch_user(current);
+	switch_uid_keyring_task(tsk, new_user);
+	tsk->user = new_user;
+	sched_switch_user(tsk);
 
 	/*
 	 * We need to synchronize with __sigqueue_alloc()
@@ -479,38 +479,16 @@ void switch_uid(struct user_struct *new_user)
 	 * structure.
 	 */
 	smp_mb();
-	spin_unlock_wait(&current->sighand->siglock);
+	spin_unlock_wait(&tsk->sighand->siglock);
 
 	free_uid(old_user);
-	suid_keys(current);
+	suid_keys(tsk);
 }
 
-#ifdef CONFIG_USER_NS
-void release_uids(struct user_namespace *ns)
+void switch_uid(struct user_struct *new_user)
 {
-	int i;
-	unsigned long flags;
-	struct hlist_head *head;
-	struct hlist_node *nd;
-
-	spin_lock_irqsave(&uidhash_lock, flags);
-	/*
-	 * collapse the chains so that the user_struct-s will
-	 * be still alive, but not in hashes. subsequent free_uid()
-	 * will free them.
-	 */
-	for (i = 0; i < UIDHASH_SZ; i++) {
-		head = ns->uidhash_table + i;
-		while (!hlist_empty(head)) {
-			nd = head->first;
-			hlist_del_init(nd);
-		}
-	}
-	spin_unlock_irqrestore(&uidhash_lock, flags);
-
-	free_uid(ns->root_user);
+	task_switch_uid(current, new_user);
 }
-#endif
 
 static int __init uid_cache_init(void)
 {
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index e8db443..0045dd0 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -16,14 +16,17 @@
  * @old_ns: namespace to clone
  * Return NULL on error (failure to kmalloc), new ns otherwise
  */
-static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
+int create_new_userns(int flags, struct task_struct *tsk)
 {
 	struct user_namespace *ns;
 	int n;
 
+	if (!(flags & CLONE_NEWUSER))
+		return 0;
+
 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
 	if (!ns)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
 	kref_init(&ns->kref);
 
@@ -34,37 +37,19 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 	ns->root_user = alloc_uid(ns, 0);
 	if (!ns->root_user) {
 		kfree(ns);
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	}
 
 	/* pin the creating user */
-	ns->creator = current->user;
+	ns->creator = tsk->user;
 	atomic_inc(&ns->creator->__count);
 
-	/*
-	 * The alloc_uid() incremented the userns refcount,
-	 * so drop it again 
-	 */
+	/* alloc_uid() incremented the userns refcount.  drop it again */
 	put_user_ns(ns);
 
-	switch_uid(ns->root_user);
-	return ns;
-}
-
-struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
-{
-	struct user_namespace *new_ns;
-
-	BUG_ON(!old_ns);
-	get_user_ns(old_ns);
-
-	if (!(flags & CLONE_NEWUSER))
-		return old_ns;
-
-	new_ns = clone_user_ns(old_ns);
+	task_switch_uid(tsk, ns->root_user);
 
-	put_user_ns(old_ns);
-	return new_ns;
+	return 0;
 }
 
 void free_user_ns(struct kref *kref)
@@ -72,7 +57,6 @@ void free_user_ns(struct kref *kref)
 	struct user_namespace *ns;
 
 	ns = container_of(kref, struct user_namespace, kref);
-	release_uids(ns);
 	free_uid(ns->creator);
 	kfree(ns);
 }
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 5be6d01..8d1cfb2 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -119,7 +119,8 @@ error:
 /*
  * deal with the UID changing
  */
-void switch_uid_keyring(struct user_struct *new_user)
+void switch_uid_keyring_task(struct task_struct *task,
+				struct user_struct *new_user)
 {
 #if 0 /* do nothing for now */
 	struct key *old;
@@ -142,6 +143,10 @@ void switch_uid_keyring(struct user_struct *new_user)
 
 } /* end switch_uid_keyring() */
 
+void switch_uid_keyring(struct user_struct *new_user)
+{
+	switch_uid_keyring_task(current, new_user);
+}
 /*****************************************************************************/
 /*
  * install a fresh thread keyring, discarding the old one
-- 
1.5.4.3

[PATCH 3/3] user namespaces: enforce user namespaces for file permission

[Serge E. Hallyn]

Add a user_ns to the sb.  It is always set to the user_ns of the task which
mounted the sb.

Define 3 new super_operations.  convert_uid() and convert_gid() take a uid
or gid from an inode on the sb's fs, and attempt to convert them into ids
meaningful in the user namespace passed in, which presumably is current's.
is_capable() checks whether current has the requested capability with respect
to the sb's fs, which is dependent upon the relationship between current's
user_ns and those which the sb knows about.

If the sb isn't user ns aware - which none are right now - then the new
super_operations won't be defined.  If in that case current and sb have
different user namespaces, then the userids can't be compared.

If current's and sb's userids can't be compared, then current will get
'user other' (we usually say 'nobody') permissions to the inode.

Signed-off-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 fs/namei.c         |   33 ++++++++++++++++++++++---
 fs/super.c         |    3 ++
 include/linux/fs.h |   68 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 100 insertions(+), 4 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 4ea63ed..e17bc96 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -183,10 +183,32 @@ int generic_permission(struct inode *inode, int mask,
 		int (*check_acl)(struct inode *inode, int mask))
 {
 	umode_t			mode = inode->i_mode;
+	uid_t			iuid;
+	gid_t			igid;
+	int			ret;
+	int			good_userns = 1;
+	struct			super_block *sb = inode->i_sb;
+
+	ret = s_convert_uid(sb, current->user->user_ns,
+						inode->i_uid, &iuid);
+	if (!ret)
+		good_userns = 0;
+	ret = s_convert_gid(sb, current->user->user_ns,
+						inode->i_gid, &igid);
+	if (!ret)
+		good_userns = 0;
 
 	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
 
-	if (current->fsuid == inode->i_uid)
+	/*
+	 * If we're not in the inode's user namespace, we get
+	 * user nobody permissions, and we ignore acls
+	 * (bc serge doesn't know how to handle acls in this case)
+	 */
+	if (!good_userns)
+		goto check;
+
+	if (current->fsuid == iuid)
 		mode >>= 6;
 	else {
 		if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
@@ -197,15 +219,18 @@ int generic_permission(struct inode *inode, int mask,
 				return error;
 		}
 
-		if (in_group_p(inode->i_gid))
+		if (in_group_p(igid))
 			mode >>= 3;
 	}
 
+check:
 	/*
 	 * If the DACs are ok we don't need any capability check.
 	 */
 	if ((mask & ~mode) == 0)
 		return 0;
+	if (!good_userns)
+		return -EACCES;
 
  check_capabilities:
 	/*
@@ -214,14 +239,14 @@ int generic_permission(struct inode *inode, int mask,
 	 */
 	if (!(mask & MAY_EXEC) ||
 	    (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
-		if (capable(CAP_DAC_OVERRIDE))
+		if (s_is_capable(sb, current->user->user_ns, CAP_DAC_OVERRIDE))
 			return 0;
 
 	/*
 	 * Searching includes executable on directories, else just read.
 	 */
 	if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
-		if (capable(CAP_DAC_READ_SEARCH))
+		if (s_is_capable(sb, current->user->user_ns, CAP_DAC_READ_SEARCH))
 			return 0;
 
 	return -EACCES;
diff --git a/fs/super.c b/fs/super.c
index e931ae9..3559637 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -38,6 +38,7 @@
 #include <linux/kobject.h>
 #include <linux/mutex.h>
 #include <linux/file.h>
+#include <linux/user_namespace.h>
 #include <asm/uaccess.h>
 #include "internal.h"
 
@@ -93,6 +94,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
 		s->s_qcop = sb_quotactl_ops;
 		s->s_op = &default_op;
 		s->s_time_gran = 1000000000;
+		s->user_ns = get_user_ns(current->user->user_ns);
 	}
 out:
 	return s;
@@ -109,6 +111,7 @@ static inline void destroy_super(struct super_block *s)
 	security_sb_free(s);
 	kfree(s->s_subtype);
 	kfree(s->s_options);
+	put_user_ns(s->user_ns);
 	kfree(s);
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 580b513..a7cbcea 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1128,6 +1128,11 @@ struct super_block {
 	 * generic_show_options()
 	 */
 	char *s_options;
+
+	/*
+	 * namespace of the user which mounted the sb
+	 */
+	struct user_namespace *user_ns;
 };
 
 extern struct timespec current_fs_time(struct super_block *sb);
@@ -1320,6 +1325,9 @@ struct super_operations {
 	int (*remount_fs) (struct super_block *, int *, char *);
 	void (*clear_inode) (struct inode *);
 	void (*umount_begin) (struct super_block *);
+	int (*is_capable) (struct user_namespace *, int);
+	uid_t (*convert_uid)(struct user_namespace *, uid_t, uid_t *);
+	gid_t (*convert_gid)(struct user_namespace *, gid_t, gid_t *);
 
 	int (*show_options)(struct seq_file *, struct vfsmount *);
 	int (*show_stats)(struct seq_file *, struct vfsmount *);
@@ -1330,6 +1338,66 @@ struct super_operations {
 };
 
 /*
+ * In the next 3, i'm passing the user_ns in so that I don't need
+ * to know how to dereference struct user her (which would require
+ * #including sched.h).
+ * Note in particular that for instance in s_convert_uid, the uid is the
+ * inode->i_uid, while user_ns is current->user->user_ns.
+ */
+
+/*
+ * s_convert_uid: attempt to translate the inode's stored
+ * uid to a uid meaningful in user_ns passed in
+ * If possible, store the result in reuid and return 1
+ * Otherwise, return 0, meaningful the uid cannot be translated
+ */
+static inline int s_convert_uid(struct super_block *sb,
+		struct user_namespace *user_ns, uid_t uid, uid_t *retuid)
+{
+	if (sb->user_ns == user_ns) {
+		*retuid = uid;
+		return 1;
+	}
+	if (sb->s_op->convert_uid)
+		return sb->s_op->convert_uid(user_ns, uid, retuid);
+	return 0;
+}
+
+/*
+ * s_convert_gid: attempt to translate the inode's stored
+ * gid to a gid meaningful in user_ns passed in
+ * If possible, store the result in regid and return 1
+ * Otherwise, return 0, meaningful the gid cannot be translated
+ */
+static inline int s_convert_gid(struct super_block *sb,
+		struct user_namespace *user_ns, gid_t gid, gid_t *retgid)
+{
+	if (sb->user_ns == user_ns) {
+		*retgid = gid;
+		return 1;
+	}
+	if (sb->s_op->convert_gid)
+		return sb->s_op->convert_gid(user_ns, gid, retgid);
+	return 0;
+}
+
+/*
+ * s_is_capable: check whether current is capable with respect
+ * to the filesystem represented by sb.
+ *
+ * return 0 if false, 1 if true
+ */
+static inline int s_is_capable(struct super_block *sb,
+		struct user_namespace *user_ns, int cap)
+{
+	if (sb->user_ns == user_ns)
+		return capable(cap);
+	if (sb->s_op->is_capable)
+		return sb->s_op->is_capable(user_ns, cap);
+	return 0;
+}
+
+/*
  * Inode state bits.  Protected by inode_lock.
  *
  * Three bits determine the dirty state of the inode, I_DIRTY_SYNC,
-- 
1.5.4.3

[PATCH 2/3] user namespaces: move user_ns from nsproxy into user struct

[Serge E. Hallyn]

When we get the sysfs support needed to support fair user scheduling
along with user namespaces, then we will need to be able to get the
user namespace from the user struct.

So we need the user_ns to be a part of struct user.  Once we can
access it from tsk->user, we no longer have a use for
tsk->nsproxy->user_ns.

When a user_namespace is created, the user which created it is
marked as its 'creator'.  The user_namespace pins the creator.
Each userid in a user_ns pins the user_ns.  This keeps refcounting
nice and simple.

At the same time, this patch simplifies the refcounting.  The current
user and userns locking works as follows:

	The task pins the user struct.

	The task pins the nsproxy, the nsproxy pins the user_ns.

	When a new user_ns is created, it creates a root user for
	it, and pins it.  When the nsproxy releases the user_ns,
	the userns tries to release all its user structs.

	So you see that the refcounting "works" for now, but only
	because the nsproxy (and therefore usr_ns) and user structs
	will be freed at the same time - when the last task using
	them is released.

	Now we need to put the user_ns in the struct user.  You can
	see that will mess up the refcounting.

	Fortunately, once the user_ns is available from tsk->user,
	we don't need it in nsproxy.

	So here is how the refcounting *should* be done:

	The task pins the user struct.

	The user struct pins its user namespace.

	The user namespace pins the struct user which created it.

	A user namespace now doesn't need to release its userids,
	because it is only released when its last user disappears.

This patch makes those changes.

Signed-off-by: Serge Hallyn <serue@us.ibm.com>
---
 include/linux/init_task.h      |    1 -
 include/linux/key.h            |    3 ++
 include/linux/nsproxy.h        |    1 -
 include/linux/sched.h          |    1 +
 include/linux/user_namespace.h |   10 +++-----
 kernel/fork.c                  |    3 +-
 kernel/nsproxy.c               |   10 +-------
 kernel/sys.c                   |    4 +-
 kernel/user.c                  |   42 +++++++++------------------------------
 kernel/user_namespace.c        |   36 +++++++++------------------------
 security/keys/process_keys.c   |    7 +++++-
 11 files changed, 39 insertions(+), 79 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 021d8e7..550058b 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -57,7 +57,6 @@ extern struct nsproxy init_nsproxy;
 	.mnt_ns		= NULL,						\
 	INIT_NET_NS(net_ns)                                             \
 	INIT_IPC_NS(ipc_ns)						\
-	.user_ns	= &init_user_ns,				\
 }
 
 #define INIT_SIGHAND(sighand) {						\
diff --git a/include/linux/key.h b/include/linux/key.h
index c45c962..ba53aef 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -277,6 +277,8 @@ extern ctl_table key_sysctls[];
  * the userspace interface
  */
 extern void switch_uid_keyring(struct user_struct *new_user);
+extern void switch_uid_keyring_task(struct task_struct *tsk,
+				struct user_struct *new_user);
 extern int copy_keys(unsigned long clone_flags, struct task_struct *tsk);
 extern int copy_thread_group_keys(struct task_struct *tsk);
 extern void exit_keys(struct task_struct *tsk);
@@ -305,6 +307,7 @@ extern void key_init(void);
 #define key_ref_to_ptr(k)		({ NULL; })
 #define is_key_possessed(k)		0
 #define switch_uid_keyring(u)		do { } while(0)
+#define switch_uid_keyring_task(t,u)	do { } while(0)
 #define __install_session_keyring(t, k)	({ NULL; })
 #define copy_keys(f,t)			0
 #define copy_thread_group_keys(t)	0
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index c8a768e..afad7de 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -27,7 +27,6 @@ struct nsproxy {
 	struct ipc_namespace *ipc_ns;
 	struct mnt_namespace *mnt_ns;
 	struct pid_namespace *pid_ns;
-	struct user_namespace *user_ns;
 	struct net 	     *net_ns;
 };
 extern struct nsproxy init_nsproxy;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9bebf95..47147fb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1716,6 +1716,7 @@ static inline struct user_struct *get_uid(struct user_struct *u)
 }
 extern void free_uid(struct user_struct *);
 extern void switch_uid(struct user_struct *);
+extern void task_switch_uid(struct task_struct *tsk, struct user_struct *);
 extern void release_uids(struct user_namespace *ns);
 
 #include <asm/current.h>
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index f9477c3..1b4959d 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -27,8 +27,7 @@ static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
 	return ns;
 }
 
-extern struct user_namespace *copy_user_ns(int flags,
-					   struct user_namespace *old_ns);
+extern int create_new_userns(int flags, struct task_struct *tsk);
 extern void free_user_ns(struct kref *kref);
 
 static inline void put_user_ns(struct user_namespace *ns)
@@ -44,13 +43,12 @@ static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
 	return &init_user_ns;
 }
 
-static inline struct user_namespace *copy_user_ns(int flags,
-						  struct user_namespace *old_ns)
+static inline int create_new_userns(int flags, struct task_struct *tsk)
 {
 	if (flags & CLONE_NEWUSER)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
-	return old_ns;
+	return 0;
 }
 
 static inline void put_user_ns(struct user_namespace *ns)
diff --git a/kernel/fork.c b/kernel/fork.c
index 7ce2ebe..b5d4dc5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -941,8 +941,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	retval = -EAGAIN;
 	if (atomic_read(&p->user->processes) >=
 			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
-		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
-		    p->user != current->nsproxy->user_ns->root_user)
+		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE))
 			goto bad_fork_free;
 	}
 
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 1d3ef29..766c672 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -80,11 +80,9 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
 		goto out_pid;
 	}
 
-	new_nsp->user_ns = copy_user_ns(flags, tsk->nsproxy->user_ns);
-	if (IS_ERR(new_nsp->user_ns)) {
-		err = PTR_ERR(new_nsp->user_ns);
+	err = create_new_userns(flags, tsk);
+	if (err)
 		goto out_user;
-	}
 
 	new_nsp->net_ns = copy_net_ns(flags, tsk->nsproxy->net_ns);
 	if (IS_ERR(new_nsp->net_ns)) {
@@ -95,8 +93,6 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
 	return new_nsp;
 
 out_net:
-	if (new_nsp->user_ns)
-		put_user_ns(new_nsp->user_ns);
 out_user:
 	if (new_nsp->pid_ns)
 		put_pid_ns(new_nsp->pid_ns);
@@ -173,8 +169,6 @@ void free_nsproxy(struct nsproxy *ns)
 		put_ipc_ns(ns->ipc_ns);
 	if (ns->pid_ns)
 		put_pid_ns(ns->pid_ns);
-	if (ns->user_ns)
-		put_user_ns(ns->user_ns);
 	put_net(ns->net_ns);
 	kmem_cache_free(nsproxy_cachep, ns);
 }
diff --git a/kernel/sys.c b/kernel/sys.c
index 038a7bc..d89ddd9 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -553,13 +553,13 @@ static int set_user(uid_t new_ruid, int dumpclear)
 {
 	struct user_struct *new_user;
 
-	new_user = alloc_uid(current->nsproxy->user_ns, new_ruid);
+	new_user = alloc_uid(current->user->user_ns, new_ruid);
 	if (!new_user)
 		return -EAGAIN;
 
 	if (atomic_read(&new_user->processes) >=
 				current->signal->rlim[RLIMIT_NPROC].rlim_cur &&
-			new_user != current->nsproxy->user_ns->root_user) {
+			!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
 		free_uid(new_user);
 		return -EAGAIN;
 	}
diff --git a/kernel/user.c b/kernel/user.c
index ee841c7..d74a7a6 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -366,7 +366,7 @@ struct user_struct *find_user(uid_t uid)
 {
 	struct user_struct *ret;
 	unsigned long flags;
-	struct user_namespace *ns = current->nsproxy->user_ns;
+	struct user_namespace *ns = current->user->user_ns;
 
 	spin_lock_irqsave(&uidhash_lock, flags);
 	ret = uid_hash_find(uid, uidhashentry(ns, uid));
@@ -455,7 +455,7 @@ out_unlock:
 	return NULL;
 }
 
-void switch_uid(struct user_struct *new_user)
+void task_switch_uid(struct task_struct *tsk, struct user_struct *new_user)
 {
 	struct user_struct *old_user;
 
@@ -464,12 +464,12 @@ void switch_uid(struct user_struct *new_user)
 	 * cheaply with the new uid cache, so if it matters
 	 * we should be checking for it.  -DaveM
 	 */
-	old_user = current->user;
+	old_user = tsk->user;
 	atomic_inc(&new_user->processes);
 	atomic_dec(&old_user->processes);
-	switch_uid_keyring(new_user);
-	current->user = new_user;
-	sched_switch_user(current);
+	switch_uid_keyring_task(tsk, new_user);
+	tsk->user = new_user;
+	sched_switch_user(tsk);
 
 	/*
 	 * We need to synchronize with __sigqueue_alloc()
@@ -479,38 +479,16 @@ void switch_uid(struct user_struct *new_user)
 	 * structure.
 	 */
 	smp_mb();
-	spin_unlock_wait(&current->sighand->siglock);
+	spin_unlock_wait(&tsk->sighand->siglock);
 
 	free_uid(old_user);
-	suid_keys(current);
+	suid_keys(tsk);
 }
 
-#ifdef CONFIG_USER_NS
-void release_uids(struct user_namespace *ns)
+void switch_uid(struct user_struct *new_user)
 {
-	int i;
-	unsigned long flags;
-	struct hlist_head *head;
-	struct hlist_node *nd;
-
-	spin_lock_irqsave(&uidhash_lock, flags);
-	/*
-	 * collapse the chains so that the user_struct-s will
-	 * be still alive, but not in hashes. subsequent free_uid()
-	 * will free them.
-	 */
-	for (i = 0; i < UIDHASH_SZ; i++) {
-		head = ns->uidhash_table + i;
-		while (!hlist_empty(head)) {
-			nd = head->first;
-			hlist_del_init(nd);
-		}
-	}
-	spin_unlock_irqrestore(&uidhash_lock, flags);
-
-	free_uid(ns->root_user);
+	task_switch_uid(current, new_user);
 }
-#endif
 
 static int __init uid_cache_init(void)
 {
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index f9f7ad7..d59f193 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -15,14 +15,17 @@
  * @old_ns: namespace to clone
  * Return NULL on error (failure to kmalloc), new ns otherwise
  */
-static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
+int create_new_userns(int flags, struct task_struct *tsk)
 {
 	struct user_namespace *ns;
 	int n;
 
+	if (!(flags & CLONE_NEWUSER))
+		return 0;
+
 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
 	if (!ns)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
 	kref_init(&ns->kref);
 
@@ -33,37 +36,19 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 	ns->root_user = alloc_uid(ns, 0);
 	if (!ns->root_user) {
 		kfree(ns);
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	}
 
 	/* pin the creating user */
-	ns->creator = current->user;
+	ns->creator = tsk->user;
 	atomic_inc(&ns->creator->__count);
 
-	/*
-	 * The alloc_uid() incremented the userns refcount,
-	 * so drop it again
-	 */
+	/* alloc_uid() incremented the userns refcount.  drop it again */
 	put_user_ns(ns);
 
-	switch_uid(ns->root_user);
-	return ns;
-}
-
-struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
-{
-	struct user_namespace *new_ns;
-
-	BUG_ON(!old_ns);
-	get_user_ns(old_ns);
-
-	if (!(flags & CLONE_NEWUSER))
-		return old_ns;
-
-	new_ns = clone_user_ns(old_ns);
+	task_switch_uid(tsk, ns->root_user);
 
-	put_user_ns(old_ns);
-	return new_ns;
+	return 0;
 }
 
 void free_user_ns(struct kref *kref)
@@ -71,7 +56,6 @@ void free_user_ns(struct kref *kref)
 	struct user_namespace *ns;
 
 	ns = container_of(kref, struct user_namespace, kref);
-	release_uids(ns);
 	free_uid(ns->creator);
 	kfree(ns);
 }
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 5be6d01..8d1cfb2 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -119,7 +119,8 @@ error:
 /*
  * deal with the UID changing
  */
-void switch_uid_keyring(struct user_struct *new_user)
+void switch_uid_keyring_task(struct task_struct *task,
+				struct user_struct *new_user)
 {
 #if 0 /* do nothing for now */
 	struct key *old;
@@ -142,6 +143,10 @@ void switch_uid_keyring(struct user_struct *new_user)
 
 } /* end switch_uid_keyring() */
 
+void switch_uid_keyring(struct user_struct *new_user)
+{
+	switch_uid_keyring_task(current, new_user);
+}
 /*****************************************************************************/
 /*
  * install a fresh thread keyring, discarding the old one
-- 
1.5.4.3

[PATCH 2/3] user namespaces: move user_ns from nsproxy into user struct

[Serge E. Hallyn]

When we get the sysfs support needed to support fair user scheduling
along with user namespaces, then we will need to be able to get the
user namespace from the user struct.

So we need the user_ns to be a part of struct user.  Once we can
access it from tsk->user, we no longer have a use for
tsk->nsproxy->user_ns.

When a user_namespace is created, the user which created it is
marked as its 'creator'.  The user_namespace pins the creator.
Each userid in a user_ns pins the user_ns.  This keeps refcounting
nice and simple.

At the same time, this patch simplifies the refcounting.  The current
user and userns locking works as follows:

	The task pins the user struct.

	The task pins the nsproxy, the nsproxy pins the user_ns.

	When a new user_ns is created, it creates a root user for
	it, and pins it.  When the nsproxy releases the user_ns,
	the userns tries to release all its user structs.

	So you see that the refcounting "works" for now, but only
	because the nsproxy (and therefore usr_ns) and user structs
	will be freed at the same time - when the last task using
	them is released.

	Now we need to put the user_ns in the struct user.  You can
	see that will mess up the refcounting.

	Fortunately, once the user_ns is available from tsk->user,
	we don't need it in nsproxy.

	So here is how the refcounting *should* be done:

	The task pins the user struct.

	The user struct pins its user namespace.

	The user namespace pins the struct user which created it.

	A user namespace now doesn't need to release its userids,
	because it is only released when its last user disappears.

This patch makes those changes.

Signed-off-by: Serge Hallyn <serue@us.ibm.com>

---

 include/linux/init_task.h      |    1 -
 include/linux/key.h            |    3 +++
 include/linux/nsproxy.h        |    1 -
 include/linux/sched.h          |    1 +
 include/linux/user_namespace.h |   10 ++++------
 kernel/fork.c                  |    3 +--
 kernel/nsproxy.c               |   10 ++--------
 kernel/sys.c                   |    4 ++--
 kernel/user.c                  |   42 ++++++++++------------------------------
 kernel/user_namespace.c        |   36 ++++++++++------------------------
 security/keys/process_keys.c   |    7 ++++++-
 11 files changed, 39 insertions(+), 79 deletions(-)

678772929a58271cb5daf44b973b2e69d7ac7d5d
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 021d8e7..550058b 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -57,7 +57,6 @@ extern struct nsproxy init_nsproxy;
 	.mnt_ns		= NULL,						\
 	INIT_NET_NS(net_ns)                                             \
 	INIT_IPC_NS(ipc_ns)						\
-	.user_ns	= &init_user_ns,				\
 }
 
 #define INIT_SIGHAND(sighand) {						\
diff --git a/include/linux/key.h b/include/linux/key.h
index c45c962..861a383 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -277,6 +277,8 @@ extern ctl_table key_sysctls[];
  * the userspace interface
  */
 extern void switch_uid_keyring(struct user_struct *new_user);
+extern void switch_uid_keyring_task(struct task_struct *tsk,
+				struct user_struct *new_user);
 extern int copy_keys(unsigned long clone_flags, struct task_struct *tsk);
 extern int copy_thread_group_keys(struct task_struct *tsk);
 extern void exit_keys(struct task_struct *tsk);
@@ -305,6 +307,7 @@ extern void key_init(void);
 #define key_ref_to_ptr(k)		({ NULL; })
 #define is_key_possessed(k)		0
 #define switch_uid_keyring(u)		do { } while(0)
+#define switch_uid_keyring_task(t, u)	do { } while(0)
 #define __install_session_keyring(t, k)	({ NULL; })
 #define copy_keys(f,t)			0
 #define copy_thread_group_keys(t)	0
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index c8a768e..afad7de 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -27,7 +27,6 @@ struct nsproxy {
 	struct ipc_namespace *ipc_ns;
 	struct mnt_namespace *mnt_ns;
 	struct pid_namespace *pid_ns;
-	struct user_namespace *user_ns;
 	struct net 	     *net_ns;
 };
 extern struct nsproxy init_nsproxy;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1cf17d9..edf086f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1720,6 +1720,7 @@ static inline struct user_struct *get_ui
 }
 extern void free_uid(struct user_struct *);
 extern void switch_uid(struct user_struct *);
+extern void task_switch_uid(struct task_struct *tsk, struct user_struct *);
 extern void release_uids(struct user_namespace *ns);
 
 #include <asm/current.h>
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index f9477c3..1b4959d 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -27,8 +27,7 @@ static inline struct user_namespace *get
 	return ns;
 }
 
-extern struct user_namespace *copy_user_ns(int flags,
-					   struct user_namespace *old_ns);
+extern int create_new_userns(int flags, struct task_struct *tsk);
 extern void free_user_ns(struct kref *kref);
 
 static inline void put_user_ns(struct user_namespace *ns)
@@ -44,13 +43,12 @@ static inline struct user_namespace *get
 	return &init_user_ns;
 }
 
-static inline struct user_namespace *copy_user_ns(int flags,
-						  struct user_namespace *old_ns)
+static inline int create_new_userns(int flags, struct task_struct *tsk)
 {
 	if (flags & CLONE_NEWUSER)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
-	return old_ns;
+	return 0;
 }
 
 static inline void put_user_ns(struct user_namespace *ns)
diff --git a/kernel/fork.c b/kernel/fork.c
index 7ce2ebe..b5d4dc5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -941,8 +941,7 @@ static struct task_struct *copy_process(
 	retval = -EAGAIN;
 	if (atomic_read(&p->user->processes) >=
 			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
-		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
-		    p->user != current->nsproxy->user_ns->root_user)
+		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE))
 			goto bad_fork_free;
 	}
 
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 1d3ef29..766c672 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -80,11 +80,9 @@ static struct nsproxy *create_new_namesp
 		goto out_pid;
 	}
 
-	new_nsp->user_ns = copy_user_ns(flags, tsk->nsproxy->user_ns);
-	if (IS_ERR(new_nsp->user_ns)) {
-		err = PTR_ERR(new_nsp->user_ns);
+	err = create_new_userns(flags, tsk);
+	if (err)
 		goto out_user;
-	}
 
 	new_nsp->net_ns = copy_net_ns(flags, tsk->nsproxy->net_ns);
 	if (IS_ERR(new_nsp->net_ns)) {
@@ -95,8 +93,6 @@ static struct nsproxy *create_new_namesp
 	return new_nsp;
 
 out_net:
-	if (new_nsp->user_ns)
-		put_user_ns(new_nsp->user_ns);
 out_user:
 	if (new_nsp->pid_ns)
 		put_pid_ns(new_nsp->pid_ns);
@@ -173,8 +169,6 @@ void free_nsproxy(struct nsproxy *ns)
 		put_ipc_ns(ns->ipc_ns);
 	if (ns->pid_ns)
 		put_pid_ns(ns->pid_ns);
-	if (ns->user_ns)
-		put_user_ns(ns->user_ns);
 	put_net(ns->net_ns);
 	kmem_cache_free(nsproxy_cachep, ns);
 }
diff --git a/kernel/sys.c b/kernel/sys.c
index 038a7bc..d89ddd9 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -553,13 +553,13 @@ static int set_user(uid_t new_ruid, int 
 {
 	struct user_struct *new_user;
 
-	new_user = alloc_uid(current->nsproxy->user_ns, new_ruid);
+	new_user = alloc_uid(current->user->user_ns, new_ruid);
 	if (!new_user)
 		return -EAGAIN;
 
 	if (atomic_read(&new_user->processes) >=
 				current->signal->rlim[RLIMIT_NPROC].rlim_cur &&
-			new_user != current->nsproxy->user_ns->root_user) {
+			!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
 		free_uid(new_user);
 		return -EAGAIN;
 	}
diff --git a/kernel/user.c b/kernel/user.c
index ee841c7..d74a7a6 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -366,7 +366,7 @@ struct user_struct *find_user(uid_t uid)
 {
 	struct user_struct *ret;
 	unsigned long flags;
-	struct user_namespace *ns = current->nsproxy->user_ns;
+	struct user_namespace *ns = current->user->user_ns;
 
 	spin_lock_irqsave(&uidhash_lock, flags);
 	ret = uid_hash_find(uid, uidhashentry(ns, uid));
@@ -455,7 +455,7 @@ out_unlock:
 	return NULL;
 }
 
-void switch_uid(struct user_struct *new_user)
+void task_switch_uid(struct task_struct *tsk, struct user_struct *new_user)
 {
 	struct user_struct *old_user;
 
@@ -464,12 +464,12 @@ void switch_uid(struct user_struct *new_
 	 * cheaply with the new uid cache, so if it matters
 	 * we should be checking for it.  -DaveM
 	 */
-	old_user = current->user;
+	old_user = tsk->user;
 	atomic_inc(&new_user->processes);
 	atomic_dec(&old_user->processes);
-	switch_uid_keyring(new_user);
-	current->user = new_user;
-	sched_switch_user(current);
+	switch_uid_keyring_task(tsk, new_user);
+	tsk->user = new_user;
+	sched_switch_user(tsk);
 
 	/*
 	 * We need to synchronize with __sigqueue_alloc()
@@ -479,38 +479,16 @@ void switch_uid(struct user_struct *new_
 	 * structure.
 	 */
 	smp_mb();
-	spin_unlock_wait(&current->sighand->siglock);
+	spin_unlock_wait(&tsk->sighand->siglock);
 
 	free_uid(old_user);
-	suid_keys(current);
+	suid_keys(tsk);
 }
 
-#ifdef CONFIG_USER_NS
-void release_uids(struct user_namespace *ns)
+void switch_uid(struct user_struct *new_user)
 {
-	int i;
-	unsigned long flags;
-	struct hlist_head *head;
-	struct hlist_node *nd;
-
-	spin_lock_irqsave(&uidhash_lock, flags);
-	/*
-	 * collapse the chains so that the user_struct-s will
-	 * be still alive, but not in hashes. subsequent free_uid()
-	 * will free them.
-	 */
-	for (i = 0; i < UIDHASH_SZ; i++) {
-		head = ns->uidhash_table + i;
-		while (!hlist_empty(head)) {
-			nd = head->first;
-			hlist_del_init(nd);
-		}
-	}
-	spin_unlock_irqrestore(&uidhash_lock, flags);
-
-	free_uid(ns->root_user);
+	task_switch_uid(current, new_user);
 }
-#endif
 
 static int __init uid_cache_init(void)
 {
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index f9f7ad7..d59f193 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -15,14 +15,17 @@
  * @old_ns: namespace to clone
  * Return NULL on error (failure to kmalloc), new ns otherwise
  */
-static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
+int create_new_userns(int flags, struct task_struct *tsk)
 {
 	struct user_namespace *ns;
 	int n;
 
+	if (!(flags & CLONE_NEWUSER))
+		return 0;
+
 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
 	if (!ns)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
 	kref_init(&ns->kref);
 
@@ -33,37 +36,19 @@ static struct user_namespace *clone_user
 	ns->root_user = alloc_uid(ns, 0);
 	if (!ns->root_user) {
 		kfree(ns);
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	}
 
 	/* pin the creating user */
-	ns->creator = current->user;
+	ns->creator = tsk->user;
 	atomic_inc(&ns->creator->__count);
 
-	/*
-	 * The alloc_uid() incremented the userns refcount,
-	 * so drop it again
-	 */
+	/* alloc_uid() incremented the userns refcount.  drop it again */
 	put_user_ns(ns);
 
-	switch_uid(ns->root_user);
-	return ns;
-}
-
-struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
-{
-	struct user_namespace *new_ns;
-
-	BUG_ON(!old_ns);
-	get_user_ns(old_ns);
-
-	if (!(flags & CLONE_NEWUSER))
-		return old_ns;
-
-	new_ns = clone_user_ns(old_ns);
+	task_switch_uid(tsk, ns->root_user);
 
-	put_user_ns(old_ns);
-	return new_ns;
+	return 0;
 }
 
 void free_user_ns(struct kref *kref)
@@ -71,7 +56,6 @@ void free_user_ns(struct kref *kref)
 	struct user_namespace *ns;
 
 	ns = container_of(kref, struct user_namespace, kref);
-	release_uids(ns);
 	free_uid(ns->creator);
 	kfree(ns);
 }
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 5be6d01..8d1cfb2 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -119,7 +119,8 @@ error:
 /*
  * deal with the UID changing
  */
-void switch_uid_keyring(struct user_struct *new_user)
+void switch_uid_keyring_task(struct task_struct *task,
+				struct user_struct *new_user)
 {
 #if 0 /* do nothing for now */
 	struct key *old;
@@ -142,6 +143,10 @@ void switch_uid_keyring(struct user_stru
 
 } /* end switch_uid_keyring() */
 
+void switch_uid_keyring(struct user_struct *new_user)
+{
+	switch_uid_keyring_task(current, new_user);
+}
 /*****************************************************************************/
 /*
  * install a fresh thread keyring, discarding the old one
-- 
1.1.6