Rapid7 Vulnerability & Exploit Database

Ubuntu: USN-6739-1 (CVE-2021-46990): Linux kernel vulnerabilities

Free InsightVM Trial No Credit Card Necessary
2024 Attack Intel Report Latest research by Rapid7 Labs
Back to Search

Ubuntu: USN-6739-1 (CVE-2021-46990): Linux kernel vulnerabilities

Severity
4
CVSS
(AV:L/AC:M/Au:N/C:P/I:P/A:P)
Published
02/28/2024
Created
04/22/2024
Added
04/22/2024
Modified
10/23/2024

Description

In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Fix crashes when toggling entry flush barrier The entry flush mitigation can be enabled/disabled at runtime via a debugfs file (entry_flush), which causes the kernel to patch itself to enable/disable the relevant mitigations. However depending on which mitigation we're using, it may not be safe to do that patching while other CPUs are active. For example the following crash: sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20 Shows that we returned to userspace with a corrupted LR that points into the kernel, due to executing the partially patched call to the fallback entry flush (ie. we missed the LR restore). Fix it by doing the patching under stop machine. The CPUs that aren't doing the patching will be spinning in the core of the stop machine logic. That is currently sufficient for our purposes, because none of the patching we do is to that code or anywhere in the vicinity.

Solution(s)

  • ubuntu-upgrade-linux-image-4-4-0-1130-aws
  • ubuntu-upgrade-linux-image-4-4-0-1131-kvm
  • ubuntu-upgrade-linux-image-4-4-0-1168-aws
  • ubuntu-upgrade-linux-image-4-4-0-253-generic
  • ubuntu-upgrade-linux-image-4-4-0-253-lowlatency
  • ubuntu-upgrade-linux-image-aws
  • ubuntu-upgrade-linux-image-generic
  • ubuntu-upgrade-linux-image-generic-lts-xenial
  • ubuntu-upgrade-linux-image-kvm
  • ubuntu-upgrade-linux-image-lowlatency
  • ubuntu-upgrade-linux-image-lowlatency-lts-xenial
  • ubuntu-upgrade-linux-image-virtual
  • ubuntu-upgrade-linux-image-virtual-lts-xenial

With Rapid7 live dashboards, I have a clear view of all the assets on my network, which ones can be exploited, and what I need to do in order to reduce the risk in my environment in real-time. No other tool gives us that kind of value and insight.

– Scott Cheney, Manager of Information Security, Sierra View Medical Center

;