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SubjectRe: [PATCH 1/1] user namespaces: add ns to user_struct (v3)
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);
--
1.5.3.6


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