Use After Free Affecting kernel-rt-trace package, versions *


Severity

Recommended
medium

Based on CentOS security rating.

Threat Intelligence

EPSS
0.04% (6th percentile)

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  • Snyk IDSNYK-CENTOS7-KERNELRTTRACE-7807458
  • published22 Aug 2024
  • disclosed21 Aug 2024

Introduced: 21 Aug 2024

CVE-2022-48892  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

There is no fixed version for Centos:7 kernel-rt-trace.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-trace package and not the kernel-rt-trace package as distributed by Centos. See How to fix? for Centos:7 relevant fixed versions and status.

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

sched/core: Fix use-after-free bug in dup_user_cpus_ptr()

Since commit 07ec77a1d4e8 ("sched: Allow task CPU affinity to be restricted on asymmetric systems"), the setting and clearing of user_cpus_ptr are done under pi_lock for arm64 architecture. However, dup_user_cpus_ptr() accesses user_cpus_ptr without any lock protection. Since sched_setaffinity() can be invoked from another process, the process being modified may be undergoing fork() at the same time. When racing with the clearing of user_cpus_ptr in __set_cpus_allowed_ptr_locked(), it can lead to user-after-free and possibly double-free in arm64 kernel.

Commit 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask") fixes this problem as user_cpus_ptr, once set, will never be cleared in a task's lifetime. However, this bug was re-introduced in commit 851a723e45d1 ("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") which allows the clearing of user_cpus_ptr in do_set_cpus_allowed(). This time, it will affect all arches.

Fix this bug by always clearing the user_cpus_ptr of the newly cloned/forked task before the copying process starts and check the user_cpus_ptr state of the source task under pi_lock.

Note to stable, this patch won't be applicable to stable releases. Just copy the new dup_user_cpus_ptr() function over.

CVSS Scores

version 3.1