user namespace: fix copy_user_ns return value
When a CONFIG_USER_NS=n and a user tries to unshare some namespace other
than the user namespace, the dummy copy_user_ns returns NULL rather than
the old_ns.
This value then gets assigned to task->nsproxy->user_ns, so that a
subsequent setuid, which uses task->nsproxy->user_ns, causes a NULL
pointer deref.
Fix this by returning old_ns.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index bb32057..1101b0c 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -49,7 +49,7 @@
if (flags & CLONE_NEWUSER)
return ERR_PTR(-EINVAL);
- return NULL;
+ return old_ns;
}
static inline void put_user_ns(struct user_namespace *ns)