path: root/kernel/pid_namespace.c
diff options
authorEric W. Biederman <ebiederm@xmission.com>2016-09-22 20:00:36 -0500
committerEric W. Biederman <ebiederm@xmission.com>2016-09-22 20:00:36 -0500
commit78725596644be0181c46f55c52aadfb8c70bcdb7 (patch)
treebaaea28de07a45f932f7674cfcd6c83522940770 /kernel/pid_namespace.c
parent93f0a88bd4ad99a515f500a09f4a489ff03073eb (diff)
parent6ad92bf63e45f97e306da48cd1cbce6e4fef1e5d (diff)
Merge branch 'nsfs-ioctls' into HEAD
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 namesā€ 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>
Diffstat (limited to 'kernel/pid_namespace.c')
1 files changed, 25 insertions, 0 deletions
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 7542b28cc929..df9e8e9e0be7 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -405,12 +405,37 @@ 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;
const struct proc_ns_operations pidns_operations = {
.name = "pid",
.get = pidns_get,
.put = pidns_put,
.install = pidns_install,
+ .owner = pidns_owner,
+ .get_parent = pidns_get_parent,
static __init int pid_namespaces_init(void)

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