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userns: Free user namespaces in process context

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Add the necessary boiler plate to move freeing of user namespaces into
work queue and thus into process context where things can sleep.

This is a necessary precursor to per user namespace sysctls.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-07-30 13:53:37 -05:00
parent 13bcc6a285
commit b032132c3c
2 changed files with 14 additions and 5 deletions
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5
include/linux/user_namespace.h
View file

@ -39,6 +39,7 @@ struct user_namespace {
struct key *persistent_keyring_register;
struct rw_semaphore persistent_keyring_register_sem;
#endif
struct work_struct work;
};
extern struct user_namespace init_user_ns;
@ -54,12 +55,12 @@ static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
extern int create_user_ns(struct cred *new);
extern int unshare_userns(unsigned long unshare_flags, struct cred **new_cred);
extern void free_user_ns(struct user_namespace *ns);
extern void __put_user_ns(struct user_namespace *ns);
static inline void put_user_ns(struct user_namespace *ns)
{
if (ns && atomic_dec_and_test(&ns->count))
free_user_ns(ns);
__put_user_ns(ns);
}
struct seq_operations;

14
kernel/user_namespace.c
View file

@ -29,6 +29,7 @@ static DEFINE_MUTEX(userns_state_mutex);
static bool new_idmap_permitted(const struct file *file,
struct user_namespace *ns, int cap_setid,
struct uid_gid_map *map);
static void free_user_ns(struct work_struct *work);
static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
{
@ -101,6 +102,7 @@ int create_user_ns(struct cred *new)
ns->level = parent_ns->level + 1;
ns->owner = owner;
ns->group = group;
INIT_WORK(&ns->work, free_user_ns);
/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
mutex_lock(&userns_state_mutex);
@ -135,9 +137,10 @@ int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
return err;
}
void free_user_ns(struct user_namespace *ns)
static void free_user_ns(struct work_struct *work)
{
struct user_namespace *parent;
struct user_namespace *parent, *ns =
container_of(work, struct user_namespace, work);
do {
parent = ns->parent;
@ -149,7 +152,12 @@ void free_user_ns(struct user_namespace *ns)
ns = parent;
} while (atomic_dec_and_test(&parent->count));
}
EXPORT_SYMBOL(free_user_ns);
void __put_user_ns(struct user_namespace *ns)
{
schedule_work(&ns->work);
}
EXPORT_SYMBOL(__put_user_ns);
static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
{