Arch Linux: 202004-3 High: linux-lts Privilege Escalation

Arch Linux Security Advisory ASA-202004-3
========================================
Severity: High
Date    : 2020-04-01
CVE-ID  : CVE-2020-8835
Package : linux-lts
Type    : privilege escalation
Remote  : No
Link    : https://security.archlinux.org/AVG-1121

Summary
======
The package linux-lts before version 5.4.28-2 is vulnerable to
privilege escalation.

Resolution
=========
Upgrade to 5.4.28-2.

# pacman -Syu "linux-lts>=5.4.28-2"

The problem has been fixed upstream but no release is available yet.

Workaround
=========
BPF access can be restricted to privileged users by setting
kernel.unprivileged_bpf_disabled to 1:

# sysctl -w kernel.unprivileged_bpf_disabled=1

Description
==========
An out-of-bounds access flaw was found in the Linux kernel’s
implementation of the eBPF code verifier, where an incorrect register
bounds calculation while checking 32-bit instructions in an eBPF
program occurs. This flaw allows an unprivileged user or process to
execute eBPF programs to crash the kernel, resulting in a denial of
service or potentially gaining root privileges on the system.

Impact
=====
An unprivileged local user or process can crash the kernel, resulting
in a denial of service, or potentially gain root privileges on the
system.

References
=========
https://www.thezdi.com/blog/2020/3/19/pwn2own-2020-day-one-results
https://lore.kernel.org/bpf/This email address is being protected from spambots. You need JavaScript enabled to view it./T/
https://www.openwall.com/lists/oss-security/2020/03/30/3
https://security.archlinux.org/CVE-2020-8835