Merge tag 'selinux-pr-20181022' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux

Pull SELinux updates from Paul Moore:
 "Three SELinux patches for v4.20, all fall under the bug-fix or
  behave-better category, which is good. All three have pretty good
  descriptions too, which is even better"

* tag 'selinux-pr-20181022' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: Add __GFP_NOWARN to allocation at str_read()
  selinux: refactor mls_context_to_sid() and make it stricter
  selinux: fix mounting of cgroup2 under older policies

security/selinux/hooks.c

@@ -1508,6 +1508,11 @@ static int selinux_genfs_get_sid(struct dentry *dentry,
 		}
 		rc = security_genfs_sid(&selinux_state, sb->s_type->name,
 					path, tclass, sid);
+		if (rc == -ENOENT) {
+			/* No match in policy, mark as unlabeled. */
+			*sid = SECINITSID_UNLABELED;
+			rc = 0;
+		}
 	}
 	free_page((unsigned long)buffer);
 	return rc;