mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-27 11:19:37 +00:00
![Andrei Vagin](/assets/img/avatar_default.png)
Time Namespace isolates clock values. The kernel provides access to several clocks CLOCK_REALTIME, CLOCK_MONOTONIC, CLOCK_BOOTTIME, etc. CLOCK_REALTIME System-wide clock that measures real (i.e., wall-clock) time. CLOCK_MONOTONIC Clock that cannot be set and represents monotonic time since some unspecified starting point. CLOCK_BOOTTIME Identical to CLOCK_MONOTONIC, except it also includes any time that the system is suspended. For many users, the time namespace means the ability to changes date and time in a container (CLOCK_REALTIME). Providing per namespace notions of CLOCK_REALTIME would be complex with a massive overhead, but has a dubious value. But in the context of checkpoint/restore functionality, monotonic and boottime clocks become interesting. Both clocks are monotonic with unspecified starting points. These clocks are widely used to measure time slices and set timers. After restoring or migrating processes, it has to be guaranteed that they never go backward. In an ideal case, the behavior of these clocks should be the same as for a case when a whole system is suspended. All this means that it is required to set CLOCK_MONOTONIC and CLOCK_BOOTTIME clocks, which can be achieved by adding per-namespace offsets for clocks. A time namespace is similar to a pid namespace in the way how it is created: unshare(CLONE_NEWTIME) system call creates a new time namespace, but doesn't set it to the current process. Then all children of the process will be born in the new time namespace, or a process can use the setns() system call to join a namespace. This scheme allows setting clock offsets for a namespace, before any processes appear in it. All available clone flags have been used, so CLONE_NEWTIME uses the highest bit of CSIGNAL. It means that it can be used only with the unshare() and the clone3() system calls. [ tglx: Adjusted paragraph about clone3() to reality and massaged the changelog a bit. ] Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://criu.org/Time_namespace Link: https://lists.openvz.org/pipermail/criu/2018-June/041504.html Link: https://lore.kernel.org/r/20191112012724.250792-4-dima@arista.com
186 lines
4.7 KiB
C
186 lines
4.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _LINUX_USER_NAMESPACE_H
|
|
#define _LINUX_USER_NAMESPACE_H
|
|
|
|
#include <linux/kref.h>
|
|
#include <linux/nsproxy.h>
|
|
#include <linux/ns_common.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/workqueue.h>
|
|
#include <linux/rwsem.h>
|
|
#include <linux/sysctl.h>
|
|
#include <linux/err.h>
|
|
|
|
#define UID_GID_MAP_MAX_BASE_EXTENTS 5
|
|
#define UID_GID_MAP_MAX_EXTENTS 340
|
|
|
|
struct uid_gid_extent {
|
|
u32 first;
|
|
u32 lower_first;
|
|
u32 count;
|
|
};
|
|
|
|
struct uid_gid_map { /* 64 bytes -- 1 cache line */
|
|
u32 nr_extents;
|
|
union {
|
|
struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS];
|
|
struct {
|
|
struct uid_gid_extent *forward;
|
|
struct uid_gid_extent *reverse;
|
|
};
|
|
};
|
|
};
|
|
|
|
#define USERNS_SETGROUPS_ALLOWED 1UL
|
|
|
|
#define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
|
|
|
|
struct ucounts;
|
|
|
|
enum ucount_type {
|
|
UCOUNT_USER_NAMESPACES,
|
|
UCOUNT_PID_NAMESPACES,
|
|
UCOUNT_UTS_NAMESPACES,
|
|
UCOUNT_IPC_NAMESPACES,
|
|
UCOUNT_NET_NAMESPACES,
|
|
UCOUNT_MNT_NAMESPACES,
|
|
UCOUNT_CGROUP_NAMESPACES,
|
|
UCOUNT_TIME_NAMESPACES,
|
|
#ifdef CONFIG_INOTIFY_USER
|
|
UCOUNT_INOTIFY_INSTANCES,
|
|
UCOUNT_INOTIFY_WATCHES,
|
|
#endif
|
|
UCOUNT_COUNTS,
|
|
};
|
|
|
|
struct user_namespace {
|
|
struct uid_gid_map uid_map;
|
|
struct uid_gid_map gid_map;
|
|
struct uid_gid_map projid_map;
|
|
atomic_t count;
|
|
struct user_namespace *parent;
|
|
int level;
|
|
kuid_t owner;
|
|
kgid_t group;
|
|
struct ns_common ns;
|
|
unsigned long flags;
|
|
|
|
#ifdef CONFIG_KEYS
|
|
/* List of joinable keyrings in this namespace. Modification access of
|
|
* these pointers is controlled by keyring_sem. Once
|
|
* user_keyring_register is set, it won't be changed, so it can be
|
|
* accessed directly with READ_ONCE().
|
|
*/
|
|
struct list_head keyring_name_list;
|
|
struct key *user_keyring_register;
|
|
struct rw_semaphore keyring_sem;
|
|
#endif
|
|
|
|
/* Register of per-UID persistent keyrings for this namespace */
|
|
#ifdef CONFIG_PERSISTENT_KEYRINGS
|
|
struct key *persistent_keyring_register;
|
|
#endif
|
|
struct work_struct work;
|
|
#ifdef CONFIG_SYSCTL
|
|
struct ctl_table_set set;
|
|
struct ctl_table_header *sysctls;
|
|
#endif
|
|
struct ucounts *ucounts;
|
|
int ucount_max[UCOUNT_COUNTS];
|
|
} __randomize_layout;
|
|
|
|
struct ucounts {
|
|
struct hlist_node node;
|
|
struct user_namespace *ns;
|
|
kuid_t uid;
|
|
int count;
|
|
atomic_t ucount[UCOUNT_COUNTS];
|
|
};
|
|
|
|
extern struct user_namespace init_user_ns;
|
|
|
|
bool setup_userns_sysctls(struct user_namespace *ns);
|
|
void retire_userns_sysctls(struct user_namespace *ns);
|
|
struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type);
|
|
void dec_ucount(struct ucounts *ucounts, enum ucount_type type);
|
|
|
|
#ifdef CONFIG_USER_NS
|
|
|
|
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
|
|
{
|
|
if (ns)
|
|
atomic_inc(&ns->count);
|
|
return ns;
|
|
}
|
|
|
|
extern int create_user_ns(struct cred *new);
|
|
extern int unshare_userns(unsigned long unshare_flags, struct cred **new_cred);
|
|
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))
|
|
__put_user_ns(ns);
|
|
}
|
|
|
|
struct seq_operations;
|
|
extern const struct seq_operations proc_uid_seq_operations;
|
|
extern const struct seq_operations proc_gid_seq_operations;
|
|
extern const struct seq_operations proc_projid_seq_operations;
|
|
extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *);
|
|
extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *);
|
|
extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *);
|
|
extern ssize_t proc_setgroups_write(struct file *, const char __user *, size_t, loff_t *);
|
|
extern int proc_setgroups_show(struct seq_file *m, void *v);
|
|
extern bool userns_may_setgroups(const struct user_namespace *ns);
|
|
extern bool in_userns(const struct user_namespace *ancestor,
|
|
const struct user_namespace *child);
|
|
extern bool current_in_userns(const struct user_namespace *target_ns);
|
|
struct ns_common *ns_get_owner(struct ns_common *ns);
|
|
#else
|
|
|
|
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
|
|
{
|
|
return &init_user_ns;
|
|
}
|
|
|
|
static inline int create_user_ns(struct cred *new)
|
|
{
|
|
return -EINVAL;
|
|
}
|
|
|
|
static inline int unshare_userns(unsigned long unshare_flags,
|
|
struct cred **new_cred)
|
|
{
|
|
if (unshare_flags & CLONE_NEWUSER)
|
|
return -EINVAL;
|
|
return 0;
|
|
}
|
|
|
|
static inline void put_user_ns(struct user_namespace *ns)
|
|
{
|
|
}
|
|
|
|
static inline bool userns_may_setgroups(const struct user_namespace *ns)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
static inline bool in_userns(const struct user_namespace *ancestor,
|
|
const struct user_namespace *child)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
static inline bool current_in_userns(const struct user_namespace *target_ns)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
static inline struct ns_common *ns_get_owner(struct ns_common *ns)
|
|
{
|
|
return ERR_PTR(-EPERM);
|
|
}
|
|
#endif
|
|
|
|
#endif /* _LINUX_USER_H */
|