Deadlock Affecting kernel-libbpf package, versions <0:6.1.140-154.222.amzn2023


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.03% (7th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-AMZN2023-KERNELLIBBPF-11477891
  • published5 Aug 2025
  • disclosed12 Mar 2025

Introduced: 12 Mar 2025

CVE-2025-21853  (opens in a new tab)
CWE-833  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 kernel-libbpf to version 0:6.1.140-154.222.amzn2023 or higher.
This issue was patched in ALAS2023-2025-1050.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-libbpf package and not the kernel-libbpf package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

bpf: avoid holding freeze_mutex during mmap operation

We use map->freeze_mutex to prevent races between map_freeze() and memory mapping BPF map contents with writable permissions. The way we naively do this means we'll hold freeze_mutex for entire duration of all the mm and VMA manipulations, which is completely unnecessary. This can potentially also lead to deadlocks, as reported by syzbot in [0].

So, instead, hold freeze_mutex only during writeability checks, bump (proactively) "write active" count for the map, unlock the mutex and proceed with mmap logic. And only if something went wrong during mmap logic, then undo that "write active" counter increment.

[0] https://lore.kernel.org/bpf/678dcbc9.050a0220.303755.0066.GAE@google.com/

CVSS Base Scores

version 3.1