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Date: Tue, 6 May 2008 14:03:33 -0500
From: "Serge E. Hallyn" <serue@...ibm.com>
To: Benjamin Thery <benjamin.thery@...l.net>
Cc: linux-kernel@...r.kernel.org,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Tejun Heo <htejun@...il.com>,
Greg Kroah-Hartman <gregkh@...e.de>,
Al Viro <viro@....linux.org.uk>,
Daniel Lezcano <dlezcano@...ibm.com>,
"Serge E. Hallyn" <serue@...ibm.com>,
Pavel Emelyanov <xemul@...nvz.org>, netdev@...r.kernel.org
Subject: Re: [PATCH 11/11] sysfs: user namespaces: add ns to user_struct
Quoting Benjamin Thery (benjamin.thery@...l.net):
> Add the user_namespace to user_struct.
>
> Add a user_namespace to the sysfs_tag struct.
>
> Mark the /sys/kernel/uids directory to be tagged so that processes in
> different user namespaces can remount /sys and see their own uid
> listings.
>
> Without this patch, having CONFIG_FAIR_SCHED=y makes user namespaces
> unusable, because when you
> clone(CLONE_NEWUSER)
> it will auto-create the root userid and try to create
> /sys/kernel/uids/0. Since that already exists from the parent user
> namespace, the create fails, and the clone misleadingly ends up
> returning -ENOMEM.
>
> This patch fixes the issue by allowing each user namespace to remount
> /sys, and having /sys filter the /sys/kernel/uid/ entries by user
> namespace.
>
> Signed-off-by: Serge Hallyn <serue@...ibm.com>
Benjamin,
thanks for reposting. Please do drop this patch from the set, though.
A slimmer version of it really is needed asap, but this version as
Eric had pointed out has some holdouts from my previous approach, which
I need to drop.
thanks,
-serge
> ---
> fs/dquot.c | 2 -
> fs/ioprio.c | 2 -
> fs/sysfs/mount.c | 25 +++++++++++++++++++++
> include/linux/sched.h | 3 +-
> include/linux/sysfs.h | 9 +++++++
> include/linux/types.h | 5 ++++
> include/linux/user_namespace.h | 5 ++++
> kernel/user.c | 48 ++++++++++++++++++++++++++++++++++-------
> kernel/user_namespace.c | 3 +-
> security/keys/process_keys.c | 14 +++++------
> 10 files changed, 97 insertions(+), 19 deletions(-)
>
> Index: linux-vanilla/fs/dquot.c
> ===================================================================
> --- linux-vanilla.orig/fs/dquot.c
> +++ linux-vanilla/fs/dquot.c
> @@ -968,7 +968,7 @@ static void send_warning(const struct dq
> 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);
> Index: linux-vanilla/fs/ioprio.c
> ===================================================================
> --- linux-vanilla.orig/fs/ioprio.c
> +++ linux-vanilla/fs/ioprio.c
> @@ -224,7 +224,7 @@ asmlinkage long sys_ioprio_get(int which
> 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)
> Index: linux-vanilla/fs/sysfs/mount.c
> ===================================================================
> --- linux-vanilla.orig/fs/sysfs/mount.c
> +++ linux-vanilla/fs/sysfs/mount.c
> @@ -17,6 +17,7 @@
> #include <linux/pagemap.h>
> #include <linux/init.h>
> #include <linux/nsproxy.h>
> +#include <linux/user_namespace.h>
> #include <net/net_namespace.h>
>
> #include "sysfs.h"
> @@ -81,6 +82,7 @@ static int sysfs_fill_super(struct super
> sb->s_root = root;
> sb->s_fs_info = info;
> info->tag.net_ns = hold_net(current->nsproxy->net_ns);
> + info->tag.user_ns = current->nsproxy->user_ns;
> return 0;
>
> out_err:
> @@ -100,6 +102,8 @@ static int sysfs_test_super(struct super
>
> if (task->nsproxy->net_ns != info->tag.net_ns)
> found = 0;
> + if (task->nsproxy->user_ns != info->tag.user_ns)
> + found = 0;
>
> return found;
> }
> @@ -214,6 +218,27 @@ static struct pernet_operations sysfs_ne
> };
> #endif
>
> +#ifdef CONFIG_USER_NS
> +void sysfs_userns_exit(struct user_namespace *user_ns)
> +{
> + /* Allow the net namespace to go away while sysfs is still mounted. */
> + struct super_block *sb;
> + printk(KERN_NOTICE "sysfs: user namespace exiting\n");
> + mutex_lock(&sysfs_rename_mutex);
> + sysfs_grab_supers();
> + mutex_lock(&sysfs_mutex);
> + list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
> + struct sysfs_super_info *info = sysfs_info(sb);
> + if (info->tag.user_ns != user_ns)
> + continue;
> + info->tag.user_ns = NULL;
> + }
> + mutex_unlock(&sysfs_mutex);
> + sysfs_release_supers();
> + mutex_unlock(&sysfs_rename_mutex);
> +}
> +#endif
> +
> int __init sysfs_init(void)
> {
> int err = -ENOMEM;
> Index: linux-vanilla/include/linux/sched.h
> ===================================================================
> --- linux-vanilla.orig/include/linux/sched.h
> +++ linux-vanilla/include/linux/sched.h
> @@ -595,7 +595,7 @@ 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;
> @@ -1697,6 +1697,7 @@ static inline struct user_struct *get_ui
> 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>
>
> Index: linux-vanilla/include/linux/sysfs.h
> ===================================================================
> --- linux-vanilla.orig/include/linux/sysfs.h
> +++ linux-vanilla/include/linux/sysfs.h
> @@ -20,6 +20,7 @@
> struct kobject;
> struct module;
> struct net;
> +struct user_namespace;
>
> /* FIXME
> * The *owner field is no longer used, but leave around
> @@ -81,6 +82,7 @@ struct sysfs_ops {
>
> struct sysfs_tag_info {
> struct net *net_ns;
> + struct user_namespace *user_ns;
> };
>
> struct sysfs_tagged_dir_operations {
> @@ -139,6 +141,9 @@ int sysfs_enable_tagging(struct kobject
>
> extern int __must_check sysfs_init(void);
>
> +struct user_namespace;
> +void sysfs_userns_exit(struct user_namespace *user_ns);
> +
> #else /* CONFIG_SYSFS */
>
> static inline int sysfs_schedule_callback(struct kobject *kobj,
> @@ -264,6 +269,10 @@ static inline int __must_check sysfs_ini
> return 0;
> }
>
> +static inline void sysfs_userns_exit(struct user_namespace *user_ns)
> +{
> +}
> +
> #endif /* CONFIG_SYSFS */
>
> #endif /* _SYSFS_H_ */
> Index: linux-vanilla/include/linux/types.h
> ===================================================================
> --- linux-vanilla.orig/include/linux/types.h
> +++ linux-vanilla/include/linux/types.h
> @@ -37,6 +37,11 @@ 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;
> +};
> +
> typedef unsigned long uintptr_t;
>
> #ifdef CONFIG_UID16
> Index: linux-vanilla/include/linux/user_namespace.h
> ===================================================================
> --- linux-vanilla.orig/include/linux/user_namespace.h
> +++ linux-vanilla/include/linux/user_namespace.h
> @@ -12,10 +12,15 @@
> struct user_namespace {
> struct kref kref;
> struct hlist_head uidhash_table[UIDHASH_SZ];
> + struct kset *kset;
> 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);
> +extern int register_user_ns_kobj(struct user_namespace *ns);
> +extern void unregister_user_ns_kobj(struct user_namespace *ns);
>
> #ifdef CONFIG_USER_NS
>
> Index: linux-vanilla/kernel/user.c
> ===================================================================
> --- linux-vanilla.orig/kernel/user.c
> +++ linux-vanilla/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_USER_SCHED
> .tg = &init_task_group,
> #endif
> @@ -71,13 +75,23 @@ static void uid_hash_remove(struct user_
> 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;
> }
> @@ -236,6 +250,23 @@ static void uids_release(struct kobject
> return;
> }
>
> +static const void *userns_sb_tag(struct sysfs_tag_info *info)
> +{
> + return info->user_ns;
> +}
> +
> +static const void *userns_kobject_tag(struct kobject *kobj)
> +{
> + struct user_struct *up;
> + up = container_of(kobj, struct user_struct, kobj);
> + return up->uid.ns;
> +}
> +
> +static struct sysfs_tagged_dir_operations userns_tagged_dir_operations = {
> + .sb_tag = userns_sb_tag,
> + .kobject_tag = userns_kobject_tag,
> +};
> +
> static struct kobj_type uids_ktype = {
> .sysfs_ops = &kobj_sysfs_ops,
> .default_attrs = uids_attributes,
> @@ -246,19 +277,19 @@ static struct kobj_type uids_ktype = {
> static int uids_user_create(struct user_struct *up)
> {
> struct kobject *kobj = &up->kobj;
> - int error;
> + int err;
>
> memset(kobj, 0, sizeof(struct kobject));
> kobj->kset = uids_kset;
> - error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
> - if (error) {
> + err = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid.uid);
> + if (err) {
> kobject_put(kobj);
> goto done;
> }
>
> kobject_uevent(kobj, KOBJ_ADD);
> done:
> - return error;
> + return err;
> }
>
> /* create these entries in sysfs:
> @@ -271,7 +302,7 @@ int __init uids_sysfs_init(void)
> uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
> if (!uids_kset)
> return -ENOMEM;
> -
> + sysfs_enable_tagging(&uids_kset->kobj, &userns_tagged_dir_operations);
> return uids_user_create(&root_user);
> }
>
> @@ -403,7 +434,8 @@ struct user_struct *alloc_uid(struct use
> if (!new)
> goto out_unlock;
>
> - new->uid = uid;
> + new->uid.uid = uid;
> + new->uid.ns = ns;
> atomic_set(&new->__count, 1);
>
> if (sched_create_user(new) < 0)
> Index: linux-vanilla/kernel/user_namespace.c
> ===================================================================
> --- linux-vanilla.orig/kernel/user_namespace.c
> +++ linux-vanilla/kernel/user_namespace.c
> @@ -22,7 +22,7 @@ static struct user_namespace *clone_user
> struct user_struct *new_user;
> int n;
>
> - ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
> + ns = kzalloc(sizeof(struct user_namespace), GFP_KERNEL);
> if (!ns)
> return ERR_PTR(-ENOMEM);
>
> @@ -71,6 +71,7 @@ void free_user_ns(struct kref *kref)
> struct user_namespace *ns;
>
> ns = container_of(kref, struct user_namespace, kref);
> + sysfs_userns_exit(ns);
> release_uids(ns);
> kfree(ns);
> }
> Index: linux-vanilla/security/keys/process_keys.c
> ===================================================================
> --- linux-vanilla.orig/security/keys/process_keys.c
> +++ linux-vanilla/security/keys/process_keys.c
> @@ -47,7 +47,7 @@ static int install_user_keyrings(struct
> char buf[20];
> int ret;
>
> - kenter("%p{%u}", user, user->uid);
> + kenter("%p{%u}", user, user->uid.uid);
>
> if (user->uid_keyring) {
> kleave(" = 0 [exist]");
> @@ -62,13 +62,13 @@ static int install_user_keyrings(struct
> * - there may be one in existence already as it may have been
> * pinned by a session, but the user_struct pointing to it
> * may have been destroyed by setuid */
> - sprintf(buf, "_uid.%u", user->uid);
> + sprintf(buf, "_uid.%u", user->uid.uid);
>
> uid_keyring = find_keyring_by_name(buf, true);
> if (IS_ERR(uid_keyring)) {
> - uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1,
> - tsk, KEY_ALLOC_IN_QUOTA,
> - NULL);
> + uid_keyring = keyring_alloc(buf, user->uid.uid,
> + (gid_t) -1, tsk,
> + KEY_ALLOC_IN_QUOTA, NULL);
> if (IS_ERR(uid_keyring)) {
> ret = PTR_ERR(uid_keyring);
> goto error;
> @@ -77,12 +77,12 @@ static int install_user_keyrings(struct
>
> /* get a default session keyring (which might also exist
> * already) */
> - sprintf(buf, "_uid_ses.%u", user->uid);
> + sprintf(buf, "_uid_ses.%u", user->uid.uid);
>
> session_keyring = find_keyring_by_name(buf, true);
> if (IS_ERR(session_keyring)) {
> session_keyring =
> - keyring_alloc(buf, user->uid, (gid_t) -1,
> + keyring_alloc(buf, user->uid.uid, (gid_t) -1,
> tsk, KEY_ALLOC_IN_QUOTA, NULL);
> if (IS_ERR(session_keyring)) {
> ret = PTR_ERR(session_keyring);
>
> --
--
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