CVE-2021-47342

ext4: fix possible UAF when remounting r/o a mmp-protected file system

HIGH
7.8
CVSS Score
Published: May 21, 2024 at 02:35 PM UTC
Updated: June 17, 2026 at 04:17 AM UTC
1 product affected across 1 vendorLinux Kernel

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Severity
HIGH7.8
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix possible UAF when remounting r/o a mmp-protected file system After commit 618f003199c6 ("ext4: fix memory leak in ext4_fill_super"), after the file system is remounted read-only, there is a race where the kmmpd thread can exit, causing sbi->s_mmp_tsk to point at freed memory, which the call to ext4_stop_mmpd() can trip over. Fix this by only allowing kmmpd() to exit when it is stopped via ext4_stop_mmpd(). Bug-Report-Link: <[email protected]>

Affected

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

v ≥ 5.12.18v < 5.10.775.10.51 ≤ v < 5.10.775.11 ≤ v < 5.13.35.12.18 ≤ v < 5.135.10.515.12.185e4f5138bd8522ebe231a137682d3857209a2c07618f003199c6188e01472b03cdbba227f1dc5f24cecfdb9cf9a700d1037066173abac0617f6788dfeb7b40d9d3785f7a131fb0b1f89bb6efa46c1833
Vendor states this is fixed in 61bb4a1c417e5b95d9edb4f887f131de32e419cb (fixed)
Vendor states this is fixed in 7ed572cdf11081f8f9e07abd4bea56a3f2c4edbd (fixed)
Vendor states this is fixed in b663890d854403e566169f7e90aed5cd6ff64f6b (fixed)
Affected range stops below 5.10.77, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.13, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.13.3, so it looks safe — our inference, not a vendor statement

References (3)

Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/61bb4a1c417e5b95d9edb4f887f131de32e419cb
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/7ed572cdf11081f8f9e07abd4bea56a3f2c4edbd
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/b663890d854403e566169f7e90aed5cd6ff64f6b

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

Quick Info

StatusANALYZED
CWE
CWE-416

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