From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)
To: Linux Containers
<containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
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mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
Kirill Tkhai <ktkhai-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>,
agruenba-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Subject: [PATCH] userns,pidns: Verify the userns for new pid namespaces
Date: Sat, 29 Apr 2017 14:25:24 -0500 [thread overview]
Message-ID: <87vapnrp7f.fsf_-_@xmission.com> (raw)
In-Reply-To: <8737crt4dz.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> (Eric W. Biederman's message of "Sat, 29 Apr 2017 14:12:08 -0500")
It is pointless and confusing to allow a pid namespace hierarchy and
the user namespace hierarchy to get out of sync. The owner of a child
pid namespace should be the owner of the parent pid namespace or
a descendant of the owner of the parent pid namespace.
Otherwise it is possible to construct scenarios where it is legal to
do something in a parent pid namespace but in a child pid namespace.
It requires use of setns into a pid namespace (but not into a user
namespace) to create such a scenario.
Add the function in_userns to help in making this determination.
Signed-off-by: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
---
While review a patch from Kiril Tkhai I realized we were missing this
sanity check....
include/linux/user_namespace.h | 8 +++++++-
kernel/pid_namespace.c | 4 ++++
kernel/user_namespace.c | 18 ++++++++++++------
3 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 32354b4b4b2b..497ed50004db 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -112,8 +112,9 @@ extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_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
@@ -144,6 +145,11 @@ static inline bool userns_may_setgroups(const struct user_namespace *ns)
return true;
}
+static inline bool in_userns(const struct user_namespace *target_ns)
+{
+ return true;
+}
+
static inline bool current_in_userns(const struct user_namespace *target_ns)
{
return true;
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index de461aa0bf9a..749147f5a613 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -101,6 +101,10 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
int i;
int err;
+ err = -EINVAL;
+ if (!in_userns(parent_pid_ns->user_ns, user_ns))
+ goto out;
+
err = -ENOSPC;
if (level > MAX_PID_NS_LEVEL)
goto out;
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 2f735cbe05e8..7d8658fbabc8 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -986,19 +986,25 @@ bool userns_may_setgroups(const struct user_namespace *ns)
}
/*
- * Returns true if @ns is the same namespace as or a descendant of
- * @target_ns.
+ * Returns true if @child is the same namespace or a descendant of
+ * @ancestor.
*/
-bool current_in_userns(const struct user_namespace *target_ns)
+bool in_userns(const struct user_namespace *ancestor,
+ const struct user_namespace *child)
{
- struct user_namespace *ns;
- for (ns = current_user_ns(); ns; ns = ns->parent) {
- if (ns == target_ns)
+ const struct user_namespace *ns;
+ for (ns = child; ns; ns = ns->parent) {
+ if (ns == ancestor)
return true;
}
return false;
}
+bool current_in_userns(const struct user_namespace *target_ns)
+{
+ return in_userns(target_ns, current_user_ns());
+}
+
static inline struct user_namespace *to_user_ns(struct ns_common *ns)
{
return container_of(ns, struct user_namespace, ns);
--
2.10.1
next prev parent reply other threads:[~2017-04-29 19:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-27 12:32 [PATCH v3] pid_ns: Introduce ioctl to set vector of ns_last_pid's on ns hierarhy Kirill Tkhai
[not found] ` <149329634856.21195.14196911999722279118.stgit-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2017-04-27 15:15 ` Eric W. Biederman
[not found] ` <87mvb16fv7.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-04-27 15:52 ` Kirill Tkhai
[not found] ` <12a73543-79ea-4bac-7e96-6ab237534af2-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-04-27 16:07 ` Eric W. Biederman
[not found] ` <877f254yx0.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-04-28 9:13 ` Kirill Tkhai
[not found] ` <a9941daf-861b-453c-37b8-e95389a9959b-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-04-29 19:12 ` Eric W. Biederman
[not found] ` <8737crt4dz.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-04-29 19:25 ` Eric W. Biederman [this message]
2017-04-29 20:53 ` [PATCH] userns,pidns: Verify the userns for new pid namespaces Serge E. Hallyn
[not found] ` <20170429205325.GB1119-7LNsyQBKDXoIagZqoN9o3w@public.gmane.org>
2017-04-30 4:33 ` Eric W. Biederman
[not found] ` <87a86yseej.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-04-30 4:42 ` Eric W. Biederman
[not found] ` <87vapnrp7f.fsf_-_-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-05-02 10:03 ` Kirill Tkhai
2017-05-02 10:04 ` Kirill Tkhai
[not found] ` <fab323b8-a909-bbce-77d2-afbcd3b0452e-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-05-02 20:39 ` Eric W. Biederman
2017-05-02 9:53 ` [PATCH v3] pid_ns: Introduce ioctl to set vector of ns_last_pid's on ns hierarhy Kirill Tkhai
[not found] ` <d2b88252-d579-8deb-2c32-4118b8464b6b-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-05-02 21:26 ` Eric W. Biederman
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