Arch Linux alert ASA-202004-3 (linux-lts)

From:
             
 
Levente Polyak <anthraxx@archlinux.org> 
To:
             
 
arch-security@archlinux.org 
Subject:
             
 
[ASA-202004-3] linux-lts: privilege escalation 
Date:
             
 
Wed, 1 Apr 2020 22:28:16 +0200
Message-ID:
             
 
<509ebe1e-d8bc-eaae-208f-c1a57b182c8f@archlinux.org>
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-on...
https://lore.kernel.org/bpf/20200330160324.15259-1-daniel...
https://www.openwall.com/lists/oss-security/2020/03/30/3
https://security.archlinux.org/CVE-2020-8835