7872559664
From: Andrey Vagin <avagin@openvz.org>
Each namespace has an owning user namespace and now there is not way
to discover these relationships.
Pid and user namepaces are hierarchical. There is no way to discover
parent-child relationships too.
Why we may want to know relationships between namespaces?
One use would be visualization, in order to understand the running
system. Another would be to answer the question: what capability does
process X have to perform operations on a resource governed by namespace
Y?
One more use-case (which usually called abnormal) is checkpoint/restart.
In CRIU we are going to dump and restore nested namespaces.
There [1] was a discussion about which interface to choose to determing
relationships between namespaces.
Eric suggested to add two ioctl-s [2]:
> Grumble, Grumble. I think this may actually a case for creating ioctls
> for these two cases. Now that random nsfs file descriptors are bind
> mountable the original reason for using proc files is not as pressing.
>
> One ioctl for the user namespace that owns a file descriptor.
> One ioctl for the parent namespace of a namespace file descriptor.
Here is an implementaions of these ioctl-s.
$ man man7/namespaces.7
...
Since Linux 4.X, the following ioctl(2) calls are supported for
namespace file descriptors. The correct syntax is:
fd = ioctl(ns_fd, ioctl_type);
where ioctl_type is one of the following:
NS_GET_USERNS
Returns a file descriptor that refers to an owning user names‐
pace.
NS_GET_PARENT
Returns a file descriptor that refers to a parent namespace.
This ioctl(2) can be used for pid and user namespaces. For
user namespaces, NS_GET_PARENT and NS_GET_USERNS have the same
meaning.
In addition to generic ioctl(2) errors, the following specific ones
can occur:
EINVAL NS_GET_PARENT was called for a nonhierarchical namespace.
EPERM The requested namespace is outside of the current namespace
scope.
[1] https://lkml.org/lkml/2016/7/6/158
[2] https://lkml.org/lkml/2016/7/9/101
Changes for v2:
* don't return ENOENT for init_user_ns and init_pid_ns. There is nothing
outside of the init namespace, so we can return EPERM in this case too.
> The fewer special cases the easier the code is to get
> correct, and the easier it is to read. // Eric
Changes for v3:
* rename ns->get_owner() to ns->owner(). get_* usually means that it
grabs a reference.
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: "W. Trevor King" <wking@tremily.us>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
152 lines
3.7 KiB
C
152 lines
3.7 KiB
C
#ifndef _LINUX_USER_NAMESPACE_H
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#define _LINUX_USER_NAMESPACE_H
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#include <linux/kref.h>
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#include <linux/nsproxy.h>
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#include <linux/ns_common.h>
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#include <linux/sched.h>
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#include <linux/err.h>
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#define UID_GID_MAP_MAX_EXTENTS 5
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struct uid_gid_map { /* 64 bytes -- 1 cache line */
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u32 nr_extents;
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struct uid_gid_extent {
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u32 first;
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u32 lower_first;
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u32 count;
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} extent[UID_GID_MAP_MAX_EXTENTS];
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};
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#define USERNS_SETGROUPS_ALLOWED 1UL
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#define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
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struct ucounts;
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enum ucount_type {
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UCOUNT_USER_NAMESPACES,
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UCOUNT_PID_NAMESPACES,
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UCOUNT_UTS_NAMESPACES,
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UCOUNT_IPC_NAMESPACES,
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UCOUNT_NET_NAMESPACES,
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UCOUNT_MNT_NAMESPACES,
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UCOUNT_CGROUP_NAMESPACES,
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UCOUNT_COUNTS,
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};
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struct user_namespace {
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struct uid_gid_map uid_map;
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struct uid_gid_map gid_map;
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struct uid_gid_map projid_map;
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atomic_t count;
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struct user_namespace *parent;
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int level;
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kuid_t owner;
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kgid_t group;
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struct ns_common ns;
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unsigned long flags;
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/* Register of per-UID persistent keyrings for this namespace */
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#ifdef CONFIG_PERSISTENT_KEYRINGS
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struct key *persistent_keyring_register;
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struct rw_semaphore persistent_keyring_register_sem;
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#endif
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struct work_struct work;
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#ifdef CONFIG_SYSCTL
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struct ctl_table_set set;
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struct ctl_table_header *sysctls;
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#endif
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struct ucounts *ucounts;
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int ucount_max[UCOUNT_COUNTS];
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};
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struct ucounts {
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struct hlist_node node;
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struct user_namespace *ns;
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kuid_t uid;
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atomic_t count;
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atomic_t ucount[UCOUNT_COUNTS];
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};
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extern struct user_namespace init_user_ns;
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bool setup_userns_sysctls(struct user_namespace *ns);
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void retire_userns_sysctls(struct user_namespace *ns);
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struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type);
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void dec_ucount(struct ucounts *ucounts, enum ucount_type type);
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#ifdef CONFIG_USER_NS
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static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
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{
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if (ns)
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atomic_inc(&ns->count);
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return ns;
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}
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extern int create_user_ns(struct cred *new);
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extern int unshare_userns(unsigned long unshare_flags, struct cred **new_cred);
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extern void __put_user_ns(struct user_namespace *ns);
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static inline void put_user_ns(struct user_namespace *ns)
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{
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if (ns && atomic_dec_and_test(&ns->count))
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__put_user_ns(ns);
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}
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struct seq_operations;
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extern const struct seq_operations proc_uid_seq_operations;
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extern const struct seq_operations proc_gid_seq_operations;
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extern const struct seq_operations proc_projid_seq_operations;
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extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *);
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extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *);
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extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *);
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extern ssize_t proc_setgroups_write(struct file *, const char __user *, size_t, loff_t *);
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extern int proc_setgroups_show(struct seq_file *m, void *v);
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extern bool userns_may_setgroups(const struct user_namespace *ns);
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extern bool current_in_userns(const struct user_namespace *target_ns);
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struct ns_common *ns_get_owner(struct ns_common *ns);
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#else
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static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
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{
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return &init_user_ns;
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}
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static inline int create_user_ns(struct cred *new)
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{
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return -EINVAL;
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}
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static inline int unshare_userns(unsigned long unshare_flags,
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struct cred **new_cred)
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{
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if (unshare_flags & CLONE_NEWUSER)
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return -EINVAL;
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return 0;
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}
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static inline void put_user_ns(struct user_namespace *ns)
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{
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}
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static inline bool userns_may_setgroups(const struct user_namespace *ns)
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{
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return true;
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}
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static inline bool current_in_userns(const struct user_namespace *target_ns)
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{
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return true;
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}
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static inline struct ns_common *ns_get_owner(struct ns_common *ns)
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{
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return ERR_PTR(-EPERM);
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}
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#endif
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#endif /* _LINUX_USER_H */
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