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nsfs: add ioctl to get a parent namespace

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Pid and user namepaces are hierarchical. There is no way to discover
parent-child relationships.

In a future we will use this interface to dump and restore nested
namespaces.

Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Andrey Vagin 2016-09-06 00:47:15 -07:00 committed by Eric W. Biederman
parent 6786741dbf
commit a7306ed8d9
5 changed files with 27 additions and 0 deletions
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4
fs/nsfs.c
View File

@ -171,6 +171,10 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
switch (ioctl) {
case NS_GET_USERNS:
return open_related_ns(ns, ns_get_owner);
case NS_GET_PARENT:
if (!ns->ops->get_parent)
return -EINVAL;
return open_related_ns(ns, ns->ops->get_parent);
default:
return -ENOTTY;
}

1
include/linux/proc_ns.h
View File

@ -19,6 +19,7 @@ struct proc_ns_operations {
void (*put)(struct ns_common *ns);
int (*install)(struct nsproxy *nsproxy, struct ns_common *ns);
struct user_namespace *(*owner)(struct ns_common *ns);
struct ns_common *(*get_parent)(struct ns_common *ns);
};
extern const struct proc_ns_operations netns_operations;

2
include/uapi/linux/nsfs.h
View File

@ -7,5 +7,7 @@
/* Returns a file descriptor that refers to an owning user namespace */
#define NS_GET_USERNS _IO(NSIO, 0x1)
/* Returns a file descriptor that refers to a parent namespace */
#define NS_GET_PARENT _IO(NSIO, 0x2)
#endif /* __LINUX_NSFS_H */

19
kernel/pid_namespace.c
View File

@ -388,6 +388,24 @@ static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
return 0;
}
static struct ns_common *pidns_get_parent(struct ns_common *ns)
{
struct pid_namespace *active = task_active_pid_ns(current);
struct pid_namespace *pid_ns, *p;
/* See if the parent is in the current namespace */
pid_ns = p = to_pid_ns(ns)->parent;
for (;;) {
if (!p)
return ERR_PTR(-EPERM);
if (p == active)
break;
p = p->parent;
}
return &get_pid_ns(pid_ns)->ns;
}
static struct user_namespace *pidns_owner(struct ns_common *ns)
{
return to_pid_ns(ns)->user_ns;
@ -400,6 +418,7 @@ const struct proc_ns_operations pidns_operations = {
.put = pidns_put,
.install = pidns_install,
.owner = pidns_owner,
.get_parent = pidns_get_parent,
};
static __init int pid_namespaces_init(void)

1
kernel/user_namespace.c
View File

@ -1034,6 +1034,7 @@ const struct proc_ns_operations userns_operations = {
.put = userns_put,
.install = userns_install,
.owner = userns_owner,
.get_parent = ns_get_owner,
};
static __init int user_namespaces_init(void)