userns: Implement unshare of the user namespace
- Add CLONE_THREAD to the unshare flags if CLONE_NEWUSER is selected
As changing user namespaces is only valid if all there is only
a single thread.
- Restore the code to add CLONE_VM if CLONE_THREAD is selected and
the code to addCLONE_SIGHAND if CLONE_VM is selected.
Making the constraints in the code clear.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index a946077..ce92f7e 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -82,6 +82,21 @@
return 0;
}
+int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
+{
+ struct cred *cred;
+
+ if (!(unshare_flags & CLONE_NEWUSER))
+ return 0;
+
+ cred = prepare_creds();
+ if (!cred)
+ return -ENOMEM;
+
+ *new_cred = cred;
+ return create_user_ns(cred);
+}
+
void free_user_ns(struct kref *kref)
{
struct user_namespace *parent, *ns =