---
id: CVE-2026-64458
title: 'mm/damon/ops-common: handle extreme intervals in damon_hot_score()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mm/damon/ops-common: handle extreme intervals in damon_hot_score()

  Fix three issues in damon_hot_score() that comes from wrong handling of
  extreme (zero or too high) m…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f <
    58321b4e6e4f0f412069ab27ccdd56292757343a
  - >-
    Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f <
    74fef68d521150281e36cdaa20e9e1ee3e3aa146
  - >-
    Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f <
    ef2ae10a4582bc92b7e944181bbd2f87f3d30f3a
  - >-
    Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f <
    9c8f31eaae6140ecadec0c07320498a944556de2
  - >-
    Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f <
    76e415ea88d20f022ed5cfcf78c50e156a267e91
  - >-
    Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f <
    35d4a3cf70a855b50e53189ac2f8463e20a02046
  - Linux 5.16
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T16:38:57.314626Z'
published: '2026-07-25'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T16:44:52.652Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-64458'
references:
  - url: 'https://git.kernel.org/stable/c/58321b4e6e4f0f412069ab27ccdd56292757343a'
  - url: 'https://git.kernel.org/stable/c/74fef68d521150281e36cdaa20e9e1ee3e3aa146'
  - url: 'https://git.kernel.org/stable/c/ef2ae10a4582bc92b7e944181bbd2f87f3d30f3a'
  - url: 'https://git.kernel.org/stable/c/9c8f31eaae6140ecadec0c07320498a944556de2'
  - url: 'https://git.kernel.org/stable/c/76e415ea88d20f022ed5cfcf78c50e156a267e91'
  - url: 'https://git.kernel.org/stable/c/35d4a3cf70a855b50e53189ac2f8463e20a02046'
tags:
  - cve.org
epss: 0.0018
epssPercentile: 0.07644
ingestedAt: '2026-11-06T16:57:43.174Z'
---

## Overview

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

mm/damon/ops-common: handle extreme intervals in damon_hot_score()

Fix three issues in damon_hot_score() that comes from wrong handling of
extreme (zero or too high) monitoring intervals user setup.

When the user sets sampling interval zero, damon_max_nr_accesses(), which
is called from damon_hot_score(), causes a divide-by-zero.  Needless to
say, it is a problem.

When the user sets the aggregation interval zero, the function returns
zero.  It is wrong, since the real maximum nr_acceses in the setup should
be one.  Worse yet, it can cause another divide-by-zero from its caller,
damon_hot_score(), since it uses damon_max_nr_accesses() return value as a
denominator.

When the user sets the aggregation interval very high, damon_hot_score()
could return a value out of [0, DAMOS_MAX_SCORE] range.  Since the return
value is used as an index to the regions_score_histogram array, which is
DAMOS_MAX_SCORE+1 size, it causes out of bounds array access.

The issues can be relatively easily reproduced like below.  The sysfs
write permission is required, though.

    # ./damo start --damos_action lru_prio --damos_quota_space 100M \
            --damos_quota_interval 1s
    # cd /sys/kernel/mm/damon/admin/kdamonds/0
    # echo 0 > contexts/0/monitoring_attrs/intervals/sample_us
    # echo 0 > contexts/0/monitoring_attrs/intervals/aggr_us
    # echo commit > state
    # dmesg
    [...]
    [  131.329762] Oops: divide error: 0000 [#1] SMP NOPTI
    [...]
    [  131.336089] RIP: 0010:damon_hot_score+0x27/0xd0
    [...]

Fix the divide-by-zero intervals problems by explicitly handling the zero
intervals in damon_max_nr_accesses().  Fix the out-of-bound array access
by applying [0, DAMOS_MAX_SCORE] bounds before returning from
damon_hot_score().

The issue was discovered [1] by Sashiko.

## Affected

- `Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f < 58321b4e6e4f0f412069ab27ccdd56292757343a`
- `Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f < 74fef68d521150281e36cdaa20e9e1ee3e3aa146`
- `Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f < ef2ae10a4582bc92b7e944181bbd2f87f3d30f3a`
- `Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f < 9c8f31eaae6140ecadec0c07320498a944556de2`
- `Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f < 76e415ea88d20f022ed5cfcf78c50e156a267e91`
- `Linux >= 198f0f4c58b9f481e4e51c8c70a6ab9852bbab7f < 35d4a3cf70a855b50e53189ac2f8463e20a02046`
- `Linux 5.16`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.