apply commit 61cc4534b655 ("locking/lockdep: Avoid potential access of invalid memory in lock_class") to linux-5.4-stable

[Cheng Jui Wang]

Hi Reviewers,

This patch fixes a use-after-free error when /proc/lockdep is read by
user after a lockdep splat.

I checked and I think this patch can be applied to stable-5.4 and
later. 

commit: 61cc4534b6550997c97a03759ab46b29d44c0017
Subject: locking/lockdep: Avoid potential access of invalid memory in
lock_class

Thanks.
Cheng-Jui Wang