[Devel] [PATCH RHEL7 COMMIT] nsfs: add ioctl to get a parent namespace
Konstantin Khorenko
khorenko at virtuozzo.com
Thu Dec 7 13:40:14 MSK 2017
The commit is pushed to "branch-rh7-3.10.0-693.11.1.vz7.39.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.11.1.vz7.39.1
------>
commit 78a9e66ec6f01307da155953cef3b9fd8024099a
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date: Thu Dec 7 13:40:14 2017 +0300
nsfs: add ioctl to get a parent namespace
Patchset description:
ioctl: port NS_GET_USERNS and NS_GET_PARENT
Need these to be able to enter owner's userns of mountnamespace to have
privileges to unmount everything, to uncover dumpable overmounted
mounts. NS_GET_PARENT is not a must here but it is nice to have it too
for criu.
https://jira.sw.ru/browse/PSBM-57362
Rework mainstream patches as we don't have nsfs and ns_common.
Other option can be porting 10 more patches:
5d826c847b34 ("new helper: readlink_copy()")
435d5f4bb2cc ("common object embedded into various struct ....ns")
58be28256d98 ("make mntns ->get()/->put()/->install()/->inum() work with
&mnt_ns->ns")
ff24870f46d5 ("netns: switch ->get()/->put()/->install()/->inum() to
working with &net->ns")
3c0411846118 ("switch the rest of proc_ns_operations to working with
&...->ns")
64964528b24e ("make proc_ns_operations work with struct ns_common *
instead of void *")
6344c433a452 ("new helpers: ns_alloc_inum/ns_free_inum")
33c429405a2c ("copy address of proc_ns_ops into ns_common")
f77c80142e1a ("bury struct proc_ns in fs/proc")
e149ed2b805f ("take the targets of /proc/*/ns/* symlinks to separate fs")
And re-applying on top of them:
25b14e92af1a ("ns: allow ns_entries to have custom symlink content")
And porting fix as new version uses rcu:
073c516ff735 ("nsfs: mark dentry with DCACHE_RCUACCESS")
But still ioctls won't apply to clean after it, so I think complete
rework here is a better option.
Pavel Tikhomirov (3):
kernel: add a helper to get an owning user namespace for a namespace
nsfs: add ioctl to get an owning user namespace for ns file descriptor
nsfs: add ioctl to get a parent namespace
============================
This patch description:
Changes:
Replace ns_common in args to ns pointer and ns_ops, as we don't
have the former.
https://jira.sw.ru/browse/PSBM-57362
ms commit a7306ed8d94a ("nsfs: add ioctl to get a parent namespace")
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 at hallyn.com>
Signed-off-by: Andrei Vagin <avagin at openvz.org>
Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
fs/proc/namespaces.c | 6 ++++++
include/linux/proc_ns.h | 1 +
kernel/pid_namespace.c | 20 ++++++++++++++++++++
kernel/user_namespace.c | 1 +
4 files changed, 28 insertions(+)
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 121b76d3fcd0..626d943b23f8 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -19,6 +19,8 @@
/* 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)
static const struct proc_ns_operations *ns_entries[] = {
#ifdef CONFIG_NET_NS
@@ -175,6 +177,10 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
switch (ioctl) {
case NS_GET_USERNS:
return open_related_ns(mnt, ns, &userns_operations, ns_get_owner);
+ case NS_GET_PARENT:
+ if (!ns->ns_ops->get_parent)
+ return -EINVAL;
+ return open_related_ns(mnt, ns, ns->ns_ops, ns->ns_ops->get_parent);
default:
return -ENOTTY;
}
diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index 3f71f8e1aa18..af898ed6fbad 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -17,6 +17,7 @@ struct proc_ns_operations {
int (*install)(struct nsproxy *nsproxy, void *ns);
unsigned int (*inum)(void *ns);
struct user_namespace *(*owner)(void *ns);
+ void *(*get_parent)(void *ns, const struct proc_ns_operations *ns_ops);
};
struct proc_ns {
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 1bab842a8e1e..38e2c2da1417 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -426,6 +426,24 @@ static struct user_namespace *pidns_owner(void *ns)
return pid_ns->user_ns;
}
+static void *pidns_get_parent(void *ns, const struct proc_ns_operations *ns_ops)
+{
+ 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 = ((struct pid_namespace *)ns)->parent;
+ for (;;) {
+ if (!p)
+ return ERR_PTR(-EPERM);
+ if (p == active)
+ break;
+ p = p->parent;
+ }
+
+ return get_pid_ns(pid_ns);
+}
+
const struct proc_ns_operations pidns_operations = {
.name = "pid",
.type = CLONE_NEWPID,
@@ -434,6 +452,7 @@ const struct proc_ns_operations pidns_operations = {
.install = pidns_install,
.inum = pidns_inum,
.owner = pidns_owner,
+ .get_parent = pidns_get_parent,
};
const struct proc_ns_operations pidns_for_children_operations = {
@@ -445,6 +464,7 @@ const struct proc_ns_operations pidns_for_children_operations = {
.install = pidns_install,
.inum = pidns_inum,
.owner = pidns_owner,
+ .get_parent = pidns_get_parent,
};
static __init int pid_namespaces_init(void)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 9b145831e07c..87719ed7dc19 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -1096,6 +1096,7 @@ const struct proc_ns_operations userns_operations = {
.install = userns_install,
.inum = userns_inum,
.owner = userns_owner,
+ .get_parent = ns_get_owner,
};
static __init int user_namespaces_init(void)
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