Arch Linux Security Advisory ASA-202011-10
=========================================
Severity: Medium
Date    : 2020-11-10
CVE-ID  : CVE-2020-8694 CVE-2020-25704
Package : linux-hardened
Type    : multiple issues
Remote  : No
Link    : https://security.archlinux.org/AVG-1269

Summary
======
The package linux-hardened before version 5.9.8.a-1 is vulnerable to
multiple issues including denial of service and information disclosure.

Resolution
=========
Upgrade to 5.9.8.a-1.

# pacman -Syu "linux-hardened>=5.9.8.a-1"

The problems have been fixed upstream in version 5.9.8.a.

Workaround
=========
- CVE-2020-8694

A temporary measure would be to remove the ability for non-root users
to read the current RAPL energy reporting metrics.
This can be done with the command:

# sudo chmod 400 /sys/class/powercap/intel_rapl/*/energy_uj

This mitigation will only work on the current boot and will need to be
reapplied at each system boot to remain in effect.

Description
==========
- CVE-2020-8694 (information disclosure)

An information disclosure flaw was found in the Linux kernel's Intel
Running Average Power Limit (RAPL) implementation. A local non-privileged attacker could infer secrets by measuring power usage and
also infer private data by observing the power usage of calculations
performed on the data.

- CVE-2020-25704 (denial of service)

A memory leak has been found in the perf_event_parse_addr_filter
function of Linux before 5.9.7, leading to a denial of service.

Impact
=====
A local attacker might be able to exhaust the memory available on the
system, causing a denial of service, or access sensitive information by
observing the power usage.

References
=========
https://www.openwall.com/lists/oss-security/2020/11/09/1
https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=7bdb157cdebbf95a1cd94ed2e01b338714075d00
https://www.openwall.com/lists/oss-security/2020/11/10/5
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=949dd0104c496fa7c14991a23c03c62e44637e71
https://platypusattack.com/
https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00389.html
https://github.com/anthraxx/linux-hardened/commit/b72aaa9506b38e68f3476a642d0e42b3071f82bb
https://security.archlinux.org/CVE-2020-8694
https://security.archlinux.org/CVE-2020-25704