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/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 95142ca..17651f0 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -39,6 +39,7 @@
}
extern int create_user_ns(struct cred *new);
+extern int unshare_userns(unsigned long unshare_flags, struct cred **new_cred);
extern void free_user_ns(struct kref *kref);
static inline void put_user_ns(struct user_namespace *ns)
@@ -66,6 +67,14 @@
return -EINVAL;
}
+static inline int unshare_userns(unsigned long unshare_flags,
+ struct cred **new_cred)
+{
+ if (unshare_flags & CLONE_NEWUSER)
+ return -EINVAL;
+ return 0;
+}
+
static inline void put_user_ns(struct user_namespace *ns)
{
}