linux, linux-hwe-5.4, linux-hwe-5.8 regression

USN-4576-1 fixed a vulnerability in the overlay file system
implementation in the Linux kernel. Unfortunately, that fix introduced
a regression that could incorrectly deny access to overlay files in
some situations. This update fixes the problem.

We apologize for the inconvenience.

Original vulnerability details:

Giuseppe Scrivano discovered that the overlay file system in the Linux
kernel did not properly perform permission checks in some situations. A
local attacker could possibly use this to bypass intended restrictions and
gain read access to restricted files.