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Subject[PATCH 10/10] sysfs: user namespaces: add ns to user_struct
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@us.ibm.com>
---
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-mm/fs/dquot.c
===================================================================
--- linux-mm.orig/fs/dquot.c
+++ linux-mm/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-mm/fs/ioprio.c
===================================================================
--- linux-mm.orig/fs/ioprio.c
+++ linux-mm/fs/ioprio.c
@@ -226,7 +226,7 @@ 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-mm/fs/sysfs/mount.c
===================================================================
--- linux-mm.orig/fs/sysfs/mount.c
+++ linux-mm/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-mm/include/linux/sched.h
===================================================================
--- linux-mm.orig/include/linux/sched.h
+++ linux-mm/include/linux/sched.h
@@ -598,7 +598,7 @@ 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;
@@ -1675,6 +1675,7 @@ 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-mm/include/linux/sysfs.h
===================================================================
--- linux-mm.orig/include/linux/sysfs.h
+++ linux-mm/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 {
@@ -135,6 +137,9 @@ 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,
@@ -253,6 +258,10 @@ static inline void sysfs_printk_last_fil
{
}

+static inline void sysfs_userns_exit(struct user_namespace *user_ns)
+{
+}
+
#endif /* CONFIG_SYSFS */

#endif /* _SYSFS_H_ */
Index: linux-mm/include/linux/types.h
===================================================================
--- linux-mm.orig/include/linux/types.h
+++ linux-mm/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-mm/include/linux/user_namespace.h
===================================================================
--- linux-mm.orig/include/linux/user_namespace.h
+++ linux-mm/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-mm/kernel/user.c
===================================================================
--- linux-mm.orig/kernel/user.c
+++ linux-mm/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-mm/kernel/user_namespace.c
===================================================================
--- linux-mm.orig/kernel/user_namespace.c
+++ linux-mm/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-mm/security/keys/process_keys.c
===================================================================
--- linux-mm.orig/security/keys/process_keys.c
+++ linux-mm/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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