CVE-2025-39877

/// Technical 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_sh

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References