[PATCH 1/1] user namespaces: add ns to user_struct (v3)

["Serge E. Hallyn" <serue@us.ibm.com>]

Hi Dave,

does the following patch against 2.6.25-rc8 fix the problem
with clone(CLONE_NEWUSER) failing when CONFIG_FAIR_USER_SCHED=y?

thanks,
-serge

>From 1ba1ab187f2410bcee829c879fed0f2ca14a48fb Mon Sep 17 00:00:00 2001
From: sergeh@us.ibm.com <sergeh@us.ibm.com>
Date: Wed, 28 Nov 2007 14:50:54 -0800
Subject: [PATCH 1/1] user namespaces: add ns to user_struct (v3)

Add the user_namespace to user_struct.

Move /sys/kernel/uids/<uid> under
/sys/kernel/uids/<user_ns_address/<uid>

Without this patch, FAIR_USER_SCHED breaks user namespaces.
The -EEXIST for /sys/kernel/uids/<uid> causes the user
namespace creation to fail.

Changelog:
	apr 2: update to 2.6.25-rc8
	feb 4: user hash tables are separate by namespace,
		so remove ns checks from uid_hash_find().

Signed-off-by: Serge Hallyn <serue@us.ibm.com>
---
 fs/dquot.c                     |    2 +-
 fs/ioprio.c                    |    2 +-
 include/linux/sched.h          |    3 +-
 include/linux/types.h          |   10 ++++++
 include/linux/user_namespace.h |    1 +
 kernel/user.c                  |   66 +++++++++++++++++++++++++++++++++++++--
 kernel/user_namespace.c        |   14 ++++++++-
 security/keys/process_keys.c   |    8 ++--
 8 files changed, 94 insertions(+), 12 deletions(-)

diff --git a/fs/dquot.c b/fs/dquot.c
index 41b9dbd..7414e5d 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -960,7 +960,7 @@ static void send_warning(const struct dquot *dquot, const char warntype)
 		MINOR(dquot->dq_sb->s_dev));
 	if (ret)
 		goto attr_err_out;
-	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current->user->uid);
+	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current->user->uid.uid);
 	if (ret)
 		goto attr_err_out;
 	genlmsg_end(skb, msg_head);
diff --git a/fs/ioprio.c b/fs/ioprio.c
index c4a1c3c..139da15 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -224,7 +224,7 @@ asmlinkage long sys_ioprio_get(int which, int who)
 				break;
 
 			do_each_thread(g, p) {
-				if (p->uid != user->uid)
+				if (!task_user_equiv(p, user))
 					continue;
 				tmpio = get_task_ioprio(p);
 				if (tmpio < 0)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6a1e7af..1a25884 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -589,7 +589,7 @@ struct user_struct {
 
 	/* Hash table maintenance information */
 	struct hlist_node uidhash_node;
-	uid_t uid;
+	struct k_uid_t uid;
 
 #ifdef CONFIG_USER_SCHED
 	struct task_group *tg;
@@ -1654,6 +1654,7 @@ 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 release_uids(struct user_namespace *ns);
+extern int task_user_equiv(struct task_struct *tsk, struct user_struct *u);
 
 #include <asm/current.h>
 
diff --git a/include/linux/types.h b/include/linux/types.h
index 9dc2346..987e58d 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -37,6 +37,16 @@ typedef __kernel_gid32_t	gid_t;
 typedef __kernel_uid16_t        uid16_t;
 typedef __kernel_gid16_t        gid16_t;
 
+struct k_uid_t {
+	uid_t uid;
+	struct user_namespace *ns;
+};
+
+struct k_gid_t {
+	gid_t gid;
+	struct user_namespace *ns;
+};
+
 typedef unsigned long		uintptr_t;
 
 #ifdef CONFIG_UID16
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index b5f41d4..207cd20 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -12,6 +12,7 @@
 struct user_namespace {
 	struct kref		kref;
 	struct hlist_head	uidhash_table[UIDHASH_SZ];
+	struct kobject		kobject;
 	struct user_struct	*root_user;
 };
 
diff --git a/kernel/user.c b/kernel/user.c
index 7132022..3142b08 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -53,6 +53,10 @@ struct user_struct root_user = {
 	.files		= ATOMIC_INIT(0),
 	.sigpending	= ATOMIC_INIT(0),
 	.locked_shm     = 0,
+	.uid		= {
+		.uid = 0,
+		.ns = &init_user_ns,
+	},
 #ifdef CONFIG_KEYS
 	.uid_keyring	= &root_user_keyring,
 	.session_keyring = &root_session_keyring,
@@ -75,13 +79,30 @@ static void uid_hash_remove(struct user_struct *up)
 	hlist_del_init(&up->uidhash_node);
 }
 
-static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
+int k_uid_equiv(struct k_uid_t a, struct k_uid_t b)
+{
+	if (a.uid == b.uid && a.ns == b.ns)
+		return 1;
+	return 0;
+}
+
+int task_user_equiv(struct task_struct *tsk, struct user_struct *u)
+{
+	if (tsk->uid != u->uid.uid)
+		return 0;
+	if (tsk->nsproxy->user_ns != u->uid.ns)
+		return 0;
+	return 1;
+}
+
+static struct user_struct *uid_hash_find(uid_t uid,
+				struct hlist_head *hashent)
 {
 	struct user_struct *user;
 	struct hlist_node *h;
 
 	hlist_for_each_entry(user, h, hashent, uidhash_node) {
-		if (user->uid == uid) {
+		if (user->uid.uid == uid) {
 			atomic_inc(&user->__count);
 			return user;
 		}
@@ -226,7 +247,8 @@ static int uids_user_create(struct user_struct *up)
 
 	memset(kobj, 0, sizeof(struct kobject));
 	kobj->kset = uids_kset;
-	error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
+	error = kobject_init_and_add(kobj, &uids_ktype, &up->uid.ns->kobject,
+				     "%d", up->uid.uid);
 	if (error) {
 		kobject_put(kobj);
 		goto done;
@@ -237,6 +259,9 @@ done:
 	return error;
 }
 
+int register_user_ns_kobj(struct user_namespace *ns);
+void unregister_user_ns_kobj(struct user_namespace *ns);
+
 /* create these entries in sysfs:
  * 	"/sys/kernel/uids" directory
  * 	"/sys/kernel/uids/0" directory (for root user)
@@ -244,10 +269,16 @@ done:
  */
 int __init uids_sysfs_init(void)
 {
+	int error;
+
 	uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
 	if (!uids_kset)
 		return -ENOMEM;
 
+	error = register_user_ns_kobj(&init_user_ns);
+	if (error)
+		return error;
+
 	return uids_user_create(&root_user);
 }
 
@@ -305,6 +336,30 @@ static inline void free_user(struct user_struct *up, unsigned long flags)
 	schedule_work(&up->work);
 }
 
+int register_user_ns_kobj(struct user_namespace *ns)
+{
+	struct kobject *obj = &ns->kobject;
+	int error;
+
+	obj->kset = uids_kset;
+
+	error = kobject_init_and_add(obj, &uids_ktype, &uids_kset->kobj,
+				     "%lx", (unsigned long)ns);
+	if (error)
+		return error;
+
+	kobject_uevent(obj, KOBJ_ADD);
+
+	return 0;
+}
+
+void unregister_user_ns_kobj(struct user_namespace *ns)
+{
+	struct kobject *obj = &ns->kobject;
+	kobject_uevent(obj, KOBJ_REMOVE);
+	kobject_del(obj);
+}
+
 #else	/* CONFIG_USER_SCHED && CONFIG_SYSFS */
 
 int uids_sysfs_init(void) { return 0; }
@@ -326,6 +381,8 @@ static inline void free_user(struct user_struct *up, unsigned long flags)
 	kmem_cache_free(uid_cachep, up);
 }
 
+int register_user_ns_kobj(struct user_namespace *ns) { return 0; }
+void unregister_user_ns_kobj(struct user_namespace *ns) {}
 #endif
 
 /*
@@ -379,7 +436,8 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
 		if (!new)
 			goto out_unlock;
 
-		new->uid = uid;
+		new->uid.uid = uid;
+		new->uid.ns = ns;
 		atomic_set(&new->__count, 1);
 		atomic_set(&new->processes, 0);
 		atomic_set(&new->files, 0);
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 4c90062..7dc6cc7 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -10,6 +10,9 @@
 #include <linux/nsproxy.h>
 #include <linux/user_namespace.h>
 
+int register_user_ns_kobj(struct user_namespace *ns);
+void unregister_user_ns_kobj(struct user_namespace *ns);
+
 /*
  * Clone a new ns copying an original user ns, setting refcount to 1
  * @old_ns: namespace to clone
@@ -19,12 +22,16 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 {
 	struct user_namespace *ns;
 	struct user_struct *new_user;
-	int n;
+	int n, err;
 
 	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
 	if (!ns)
 		return ERR_PTR(-ENOMEM);
 
+	err = register_user_ns_kobj(ns);
+	if (err)
+		goto out_free_ns;
+
 	kref_init(&ns->kref);
 
 	for (n = 0; n < UIDHASH_SZ; ++n)
@@ -47,6 +54,10 @@ static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
 
 	switch_uid(new_user);
 	return ns;
+
+out_free_ns:
+	kfree(ns);
+	return ERR_PTR(err);
 }
 
 struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
@@ -71,5 +82,6 @@ void free_user_ns(struct kref *kref)
 
 	ns = container_of(kref, struct user_namespace, kref);
 	release_uids(ns);
+	unregister_user_ns_kobj(ns);
 	kfree(ns);
 }
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index c886a2b..0343a52 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -75,9 +75,9 @@ int alloc_uid_keyring(struct user_struct *user,
 	int ret;
 
 	/* concoct a default session keyring */
-	sprintf(buf, "_uid_ses.%u", user->uid);
+	sprintf(buf, "_uid_ses.%u", user->uid.uid);
 
-	session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
+	session_keyring = keyring_alloc(buf, user->uid.uid, (gid_t) -1, ctx,
 					KEY_ALLOC_IN_QUOTA, NULL);
 	if (IS_ERR(session_keyring)) {
 		ret = PTR_ERR(session_keyring);
@@ -86,9 +86,9 @@ int alloc_uid_keyring(struct user_struct *user,
 
 	/* and a UID specific keyring, pointed to by the default session
 	 * keyring */
-	sprintf(buf, "_uid.%u", user->uid);
+	sprintf(buf, "_uid.%u", user->uid.uid);
 
-	uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
+	uid_keyring = keyring_alloc(buf, user->uid.uid, (gid_t) -1, ctx,
 				    KEY_ALLOC_IN_QUOTA, session_keyring);
 	if (IS_ERR(uid_keyring)) {
 		key_put(session_keyring);
-- 
1.5.3.6