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

[Dave Leskovec <dlesko@linux.vnet.ibm.com>]

Hi Serge,

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

Serge E. Hallyn wrote:
> Quoting 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?
> 
> 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: 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 (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 <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 |    3 ++
>  kernel/user.c                  |   56 +++++++++++++++++++++++++++++++++++++---
>  kernel/user_namespace.c        |   13 ++++++++-
>  security/keys/process_keys.c   |    8 +++---
>  8 files changed, 84 insertions(+), 13 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..f0636d7 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -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
> 
> diff --git a/kernel/user.c b/kernel/user.c
> index 7132022..cd6bb89 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 +79,23 @@ 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);
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index 4c90062..0ea3bf6 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -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);
>  }
> 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);

-- 
Best Regards,
Dave Leskovec
IBM Linux Technology Center
Open Virtualization