user namespaces: add ns to user_struct (v3)

From 1ba1ab187f2410bcee829c879fed0f2ca14a48fb Mon Sep 17 00:00:00 2001

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?

From 40176b1cc0c1a9c24e8a0b572dce9ab60a8a99df Mon Sep 17 00:00:00 2001

Quoted 4 lines · Serge E. Hallyn

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?

The patch I sent didn't zero out the kobject before doing kbobject_init_and_add(), so that a kfree(kobj->name) during the registration causes an occasional oops. The following patch fixes that. Dave, please give it a shot and let me know.

thanks,
-serge

From 40176b1cc0c1a9c24e8a0b572dce9ab60a8a99df Mon Sep 17 00:00:00 2001
From: [email protected] <[email protected]>
Date: Wed, 28 Nov 2007 14:50:54 -0800
Subject: [PATCH 1/1] user namespaces: add ns to user_struct (v4)

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 3: kzalloc user_ns to avoid kfree oops at kobject_init_and_add 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 <[email protected]>

---
 fs/dquot.c                     |    2 +-
 fs/ioprio.c                    |    2 +-
 include/linux/sched.h          |    3 +-
 include/linux/types.h          |   10 +++++++
 include/linux/user_namespace.h |    3 ++
 kernel/user.c                  |   56 +++++++++++++++++++++++++++++++++++++---
 kernel/user_namespace.c        |   13 ++++++++-
 security/keys/process_keys.c   |    8 +++---
 8 files changed, 84 insertions(+), 13 deletions(-)

fs/dquot.c +1 -1

index 41b9dbd..7414e5d 100644
@@ -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);

fs/ioprio.c +1 -1

index c4a1c3c..139da15 100644
@@ -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)

include/linux/sched.h +2 -1

index 6a1e7af..1a25884 100644
@@ -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>
 

include/linux/types.h +10 -0

index 9dc2346..987e58d 100644
@@ -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

include/linux/user_namespace.h +3 -0

index b5f41d4..f0636d7 100644
@@ -12,10 +12,13 @@
 struct user_namespace {
 	struct kref		kref;
 	struct hlist_head	uidhash_table[UIDHASH_SZ];
+	struct kobject		kobject;
 	struct user_struct	*root_user;
 };
 
 extern struct user_namespace init_user_ns;
+extern int register_user_ns_kobj(struct user_namespace *ns);
+extern void unregister_user_ns_kobj(struct user_namespace *ns);
 
 #ifdef CONFIG_USER_NS
 

kernel/user.c +52 -4

index 7132022..cd6bb89 100644
@@ -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 +79,23 @@ 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 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 +240,8 @@ 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;

@@ -244,10 +259,16 @@ 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 +326,30 @@ 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 +371,8 @@ 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 +426,8 @@ 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);

kernel/user_namespace.c +11 -2

index 4c90062..0ea3bf6 100644
@@ -19,12 +19,16 @@ 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);
+	ns = kzalloc(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 +51,10 @@ 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 +79,6 @@ 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);
 }

security/keys/process_keys.c +4 -4

index c886a2b..0343a52 100644
@@ -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);

Hi Serge,

Yep, this latest patch fixed the user namespace problem I was seeing. Thanks!