mm/damon/sysfs-schemes: delete tried region in regions_rmdirs()

Description

In the Linux kernel, the following vulnerability has been resolved: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() DAMON sysfs maintains the DAMOS tried region directory objects via a linked list. When the user requests refresh of the directories, DAMON sysfs removes all the region directories first, and then generate updated regions directory on the empty space. The removal function (damon_sysfs_scheme_regions_rm_dirs()) only puts the kobj objects. Deletion of the container region object from the linked list is done inside the kobj release callback function. If somehow the callback invocation is delayed, the list will contain regions list that gonna be freed. If the updated region directories creation is started in this situation, the list can be corrupted and use-after-free can happen. Because the kobj objects are managed by only DAMON sysfs, the issue cannot happen in normal situation. But, such delays can be made on kernels that built with CONFIG_DEBUG_KOBJECT_RELEASE. On the kernel, the issue can indeed be reproduced like below. # damo start --damos_action stat # cd /sys/kernel/mm/damon/admin/kdamonds/0/ # for i in {1..10}; do echo update_schemes_tried_regions > state; done # dmesg | grep underflow [ 89.296152] refcount_t: underflow; use-after-free. Fix the issue by removing the region object from the list when decrementing the reference count. Also update damos_sysfs_populate_region_dir() to add the region object to the list only after the kobject_init_and_add() is success, so that fail of kobject_init_and_add() is not leaving the deallocated object on the list. The issue was discovered [1] by Sashiko.

Timeline

Scores

EPSS (exploitation in 30 days)

0.12% · top 98% of all CVEs (11 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Affected products

• Linux · Linux

  • affected 9277d0367ba18ef4bb98bafb1209e715844cdf7e – < c0e37017a452addec873865c94cf7a665663a9b2
  • affected 9277d0367ba18ef4bb98bafb1209e715844cdf7e – < a5fa42214de55e43d165144727ce9facb9fc6b08
  • affected 9277d0367ba18ef4bb98bafb1209e715844cdf7e – < 0ba6c05156d9ff9fc6ca22b7690e2eec9eca66f7
  • affected 9277d0367ba18ef4bb98bafb1209e715844cdf7e – < 2c33177023c92e76806c535ddbffaa3d3fc37777
  • affected 9277d0367ba18ef4bb98bafb1209e715844cdf7e – < 441f92f7d386b85bad16de49db95a307cba048a2

• Linux · Linux

  • affected 6.2
  • unaffected < 6.2
  • unaffected 6.6.143 – ≤ 6.6.*
  • unaffected 6.12.93 – ≤ 6.12.*
  • unaffected 6.18.35 – ≤ 6.18.*
  • unaffected 7.0.12 – ≤ 7.0.*
  • unaffected 7.1 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-48648 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-64239](https://cveledger.app/badge/CVE-2026-64239.svg)](https://cveledger.app/cve/CVE-2026-64239)

Record last updated 6 Nov 2026, 16:34 UTC.