CVE-2021-46971 perf/core: Fix unconditional security_locked_down() call

2024-02-2718:47:06

Linux

github.com

linux kernel

vulnerability

perf/core

security_locked_down

selinux

lockdown hook

access control

audit record

AI Score

6.7

Confidence

Low

EPSS

Percentile

15.5%

SSVC

Exploitation

none

Automatable

Technical Impact

partial

JSON

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

perf/core: Fix unconditional security_locked_down() call

Currently, the lockdown state is queried unconditionally, even though
its result is used only if the PERF_SAMPLE_REGS_INTR bit is set in
attr.sample_type. While that doesn’t matter in case of the Lockdown LSM,
it causes trouble with the SELinux’s lockdown hook implementation.

SELinux implements the locked_down hook with a check whether the current
task’s type has the corresponding “lockdown” class permission
(“integrity” or “confidentiality”) allowed in the policy. This means
that calling the hook when the access control decision would be ignored
generates a bogus permission check and audit record.

Fix this by checking sample_type first and only calling the hook when
its result would be honored.

CNA Affected

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "b0c8fdc7fdb7",
        "lessThan": "b246759284d6",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "b0c8fdc7fdb7",
        "lessThan": "4348d3b5027b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "b0c8fdc7fdb7",
        "lessThan": "f5809ca4c311",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "b0c8fdc7fdb7",
        "lessThan": "c7b0208ee370",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "b0c8fdc7fdb7",
        "lessThan": "08ef1af4de5f",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "kernel/events/core.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.4"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.4",
        "versionType": "custom"
      },
      {
        "status": "unaffected",
        "version": "5.4.117",
        "versionType": "custom",
        "lessThanOrEqual": "5.4.*"
      },
      {
        "status": "unaffected",
        "version": "5.10.35",
        "versionType": "custom",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.11.19",
        "versionType": "custom",
        "lessThanOrEqual": "5.11.*"
      },
      {
        "status": "unaffected",
        "version": "5.12.2",
        "versionType": "custom",
        "lessThanOrEqual": "5.12.*"
      },
      {
        "status": "unaffected",
        "version": "5.13",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "kernel/events/core.c"
    ],
    "defaultStatus": "affected"
  }
]