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LinuxCVE-2022-48892

HistoryAug 21, 2024 - 7:15 a.m.

CVE-2022-48892

2024-08-2107:15:05

CWE-415

CWE-416

Linux

web.nvd.nist.gov

linux kernel

use-after-free bug

dup_user_cpus_ptr

arm64 architecture

sched_setaffinity

commit

task

cpumask

patch

CVSS3

7.8

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

AI Score

6.5

Confidence

High

EPSS

Percentile

5.1%

JSON

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.

Affected configurations

Nvd

Vulners

Node

linuxlinux_kernelRange5.15–5.15.89

linuxlinux_kernelRange5.16–6.1.7

VendorProductVersionCPE
linuxlinux_kernel*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

Vendor	Product	Version	CPE
linux	linux_kernel	*	cpe:2.3:o:linux:linux_kernel::::::::

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/sched/core.c"
    ],
    "versions": [
      {
        "version": "07ec77a1d4e8",
        "lessThan": "b22faa21b623",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "07ec77a1d4e8",
        "lessThan": "7b5cc7fd1789",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "07ec77a1d4e8",
        "lessThan": "87ca4f9efbd7",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/sched/core.c"
    ],
    "versions": [
      {
        "version": "5.15",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "5.15",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.89",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.7",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.2",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]