linux-kernel - [RFC 1/5] user namespaces: Add a user_namespace as creator/owner of uts

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Message-ID: <20101217152458.GA11162@mail.hallyn.com>
Date:	Fri, 17 Dec 2010 15:24:58 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	LSM <linux-security-module@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <michael.kerrisk@...il.com>
Subject: [RFC 1/5] user namespaces: Add a user_namespace as creator/owner
 of uts_namespace

copy_process() handles CLONE_NEWUSER before the rest of the
namespaces.  So in the case of clone(CLONE_NEWUSER|CLONE_NEWUTS)
the new uts namespace will have the new user namespace as its
owner.  That is what we want, since we want root in that new
userns to be able to have privilege over it.

Signed-off-by: Serge E. Hallyn <serge.hallyn@...onical.com>
---
 include/linux/utsname.h |    3 +++
 init/version.c          |    2 ++
 kernel/nsproxy.c        |    3 +++
 kernel/user.c           |    8 ++++++--
 kernel/utsname.c        |    4 ++++
 5 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 69f3997..85171be 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -37,9 +37,12 @@ struct new_utsname {
 #include <linux/nsproxy.h>
 #include <linux/err.h>
 
+struct user_namespace;
+
 struct uts_namespace {
 	struct kref kref;
 	struct new_utsname name;
+	struct user_namespace *user_ns;
 };
 extern struct uts_namespace init_uts_ns;
 
diff --git a/init/version.c b/init/version.c
index 79fb8c2..9eb19fb 100644
--- a/init/version.c
+++ b/init/version.c
@@ -21,6 +21,7 @@ extern int version_string(LINUX_VERSION_CODE);
 int version_string(LINUX_VERSION_CODE);
 #endif
 
+extern struct user_namespace init_user_ns;
 struct uts_namespace init_uts_ns = {
 	.kref = {
 		.refcount	= ATOMIC_INIT(2),
@@ -33,6 +34,7 @@ struct uts_namespace init_uts_ns = {
 		.machine	= UTS_MACHINE,
 		.domainname	= UTS_DOMAINNAME,
 	},
+	.user_ns = &init_user_ns,
 };
 EXPORT_SYMBOL_GPL(init_uts_ns);
 
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f74e6c0..5a22dcf 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -74,6 +74,9 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
 		err = PTR_ERR(new_nsp->uts_ns);
 		goto out_uts;
 	}
+	put_user_ns(new_nsp->uts_ns->user_ns);
+	new_nsp->uts_ns->user_ns = task_cred_xxx(tsk, user)->user_ns;
+	get_user_ns(new_nsp->uts_ns->user_ns);
 
 	new_nsp->ipc_ns = copy_ipcs(flags, tsk->nsproxy->ipc_ns);
 	if (IS_ERR(new_nsp->ipc_ns)) {
diff --git a/kernel/user.c b/kernel/user.c
index 2c7d8d5..5125681 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -17,9 +17,13 @@
 #include <linux/module.h>
 #include <linux/user_namespace.h>
 
+/*
+ * userns count is 1 for root user, 1 for init_uts_ns,
+ * and 1 for... ?
+ */
 struct user_namespace init_user_ns = {
 	.kref = {
-		.refcount	= ATOMIC_INIT(2),
+		.refcount	= ATOMIC_INIT(3),
 	},
 	.creator = &root_user,
 };
@@ -47,7 +51,7 @@ static struct kmem_cache *uid_cachep;
  */
 static DEFINE_SPINLOCK(uidhash_lock);
 
-/* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->creator */
+/* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->user_ns */
 struct user_struct root_user = {
 	.__count	= ATOMIC_INIT(2),
 	.processes	= ATOMIC_INIT(1),
diff --git a/kernel/utsname.c b/kernel/utsname.c
index 8a82b4b..a7b3a8d 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -14,6 +14,7 @@
 #include <linux/utsname.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/user_namespace.h>
 
 static struct uts_namespace *create_uts_ns(void)
 {
@@ -40,6 +41,8 @@ static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
 
 	down_read(&uts_sem);
 	memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
+	ns->user_ns = old_ns->user_ns;
+	get_user_ns(ns->user_ns);
 	up_read(&uts_sem);
 	return ns;
 }
@@ -71,5 +74,6 @@ void free_uts_ns(struct kref *kref)
 	struct uts_namespace *ns;
 
 	ns = container_of(kref, struct uts_namespace, kref);
+	put_user_ns(ns->user_ns);
 	kfree(ns);
 }
-- 
1.7.0.4

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