CVE-2025-39877
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-23

Last updated on: 2025-11-03

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: mm/damon/sysfs: fix use-after-free in state_show() state_show() reads kdamond->damon_ctx without holding damon_sysfs_lock. This allows a use-after-free race: CPU 0 CPU 1 ----- ----- state_show() damon_sysfs_turn_damon_on() ctx = kdamond->damon_ctx; mutex_lock(&damon_sysfs_lock); damon_destroy_ctx(kdamond->damon_ctx); kdamond->damon_ctx = NULL; mutex_unlock(&damon_sysfs_lock); damon_is_running(ctx); /* ctx is freed */ mutex_lock(&ctx->kdamond_lock); /* UAF */ (The race can also occur with damon_sysfs_kdamonds_rm_dirs() and damon_sysfs_kdamond_release(), which free or replace the context under damon_sysfs_lock.) Fix by taking damon_sysfs_lock before dereferencing the context, mirroring the locking used in pid_show(). The bug has existed since state_show() first accessed kdamond->damon_ctx.
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Meta Information
Published
2025-09-23
Last Modified
2025-11-03
Generated
2026-06-16
AI Q&A
2025-09-23
EPSS Evaluated
2026-06-15
NVD
CVE-2025-39877
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 6.1.153-1
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Exploitability
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability is a use-after-free race condition in the Linux kernel's mm/damon/sysfs component. Specifically, the function state_show() reads a pointer (kdamond->damon_ctx) without holding the necessary damon_sysfs_lock, which can lead to the context being freed by another thread simultaneously. This causes state_show() to access freed memory, resulting in undefined behavior or potential crashes. The issue arises because state_show() does not lock damon_sysfs_lock before dereferencing the context, unlike other functions that properly lock it.

Impact Analysis

This vulnerability can lead to use-after-free conditions in the Linux kernel, which may cause system instability, crashes, or potentially allow an attacker to execute arbitrary code or escalate privileges by exploiting the race condition. The exact impact depends on the environment and how the vulnerable code is used, but it generally undermines system reliability and security.

Mitigation Strategies

Apply the patch that fixes the use-after-free race condition by ensuring damon_sysfs_lock is held before dereferencing kdamond->damon_ctx in state_show(). This fix mirrors the locking used in pid_show() and prevents the race condition. Until patched, avoid using or exposing the affected sysfs interfaces related to damon to reduce risk.

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