CVE-2021-47461 userfaultfd: fix a race between writeprotect and exit_mmap()

2024-05-2206:23:22

Linux

github.com

linux kernel

vulnerability

userfaultfd

race

writeprotect

exit_mmap

kasan

mmget_not_zero

cve-2021-47461

AI Score

6.8

Confidence

Low

EPSS

Percentile

15.5%

SSVC

Exploitation

none

Automatable

Technical Impact

partial

JSON

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

userfaultfd: fix a race between writeprotect and exit_mmap()

A race is possible when a process exits, its VMAs are removed by
exit_mmap() and at the same time userfaultfd_writeprotect() is called.

The race was detected by KASAN on a development kernel, but it appears
to be possible on vanilla kernels as well.

Use mmget_not_zero() to prevent the race as done in other userfaultfd
operations.

CNA Affected

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "63b2d4174c4a",
        "lessThan": "3cda4bfffd4f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "63b2d4174c4a",
        "lessThan": "149958ecd062",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "63b2d4174c4a",
        "lessThan": "cb185d5f1ebf",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "fs/userfaultfd.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.7"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.7",
        "versionType": "custom"
      },
      {
        "status": "unaffected",
        "version": "5.10.76",
        "versionType": "custom",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.14.15",
        "versionType": "custom",
        "lessThanOrEqual": "5.14.*"
      },
      {
        "status": "unaffected",
        "version": "5.15",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/userfaultfd.c"
    ],
    "defaultStatus": "affected"
  }
]