CVE-2021-47461

userfaultfd: fix a race between writeprotect and exit_mmap()

MEDIUM
4.7
CVSS Score
Published: May 22, 2024 at 06:23 AM UTC
Updated: August 5, 2026 at 09:24 AM UTC
1 product affected across 1 vendorLinux Kernel

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Severity
MEDIUM4.7
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

5.11 ≤ v < 5.14.155.7 ≤ v < 5.10.765.7 ≤ v < 5.14.155.7 ≤ v < 5.155.15 rc15.15 rc25.15 rc35.15 rc45.15 rc55.15 rc663b2d4174c4ad1f40b48d7138e71bcb564c1fe03
Vendor states this is fixed in 149958ecd0627a9f1e9c678c25c665400054cd6a (fixed)
Vendor states this is fixed in 3cda4bfffd4f755645577aaa9e96a606657b4525 (fixed)
Vendor states this is fixed in cb185d5f1ebf900f4ae3bf84cee212e6dd035aca (fixed)
Vendor states this is fixed in 5.10.76 (unaffected)
Vendor states this is fixed in 5.14.15 (unaffected)
Vendor states this is fixed in 5.15 (unaffected)
Vendor states this is fixed in 5.7 (unaffected)

References (3)

Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/149958ecd0627a9f1e9c678c25c665400054cd6a
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/3cda4bfffd4f755645577aaa9e96a606657b4525
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/cb185d5f1ebf900f4ae3bf84cee212e6dd035aca

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
LOCAL
Complexity
HIGH
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-362

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