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Fencer Vulns
medium 4.7

CVE-2026-46025 json

mm/damon/core: fix damon_call() vs kdamond_fn() exit race

published 2026-05-27 5 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-32406

cvss
4.7
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 0%
public exploits
0
none known

Summary

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

mm/damon/core: fix damon_call() vs kdamond_fn() exit race

Patch series "mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit race".

damon_call() and damos_walk() can leak memory and/or deadlock when they race with kdamond terminations. Fix those.

This patch (of 2);

When kdamond_fn() main loop is finished, the function cancels all remaining damon_call() requests and unset the damon_ctx->kdamond so that API callers and API functions themselves can know the context is terminated. damon_call() adds the caller's request to the queue first. After that, it shows if the kdamond of the damon_ctx is still running (damon_ctx->kdamond is set). Only if the kdamond is running, damon_call() starts waiting for the kdamond's handling of the newly added request.

The damon_call() requests registration and damon_ctx->kdamond unset are protected by different mutexes, though. Hence, damon_call() could race with damon_ctx->kdamond unset, and result in deadlocks.

For example, let's suppose kdamond successfully finished the damon_call() requests cancelling. Right after that, damon_call() is called for the context. It registers the new request, and shows the context is still running, because damon_ctx->kdamond unset is not yet done. Hence the damon_call() caller starts waiting for the handling of the request. However, the kdamond is already on the termination steps, so it never handles the new request. As a result, the damon_call() caller threads infinitely waits.

Fix this by introducing another damon_ctx field, namely call_controls_obsolete. It is protected by the damon_ctx->call_controls_lock, which protects damon_call() requests registration. Initialize (unset) it in kdamond_fn() before letting damon_start() returns and set it just before the cancelling of remaining damon_call() requests is executed. damon_call() reads the obsolete field under the lock and avoids adding a new request.

After this change, only requests that are guaranteed to be handled or cancelled are registered. Hence the after-registration DAMON context termination check is no longer needed. Remove it together.

Note that the deadlock will not happen when damon_call() is called for repeat mode request. In tis case, damon_call() returns instead of waiting for the handling when the request registration succeeds and it shows the kdamond is running. However, if the request also has dealloc_on_cancel, the request memory would be leaked.

The issue is found by sashiko [1].

Patch / fix

  • Linux Linux 6.18.27, 7.0.4, 7.1
  • linux Debian 14 7.0.4-1

debian advisories DEBIAN-CVE-2026-46025

  • linux Ubuntu 26.04 LTS 7.0.0-27.27
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1007.7
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1010.10
  • linux-raspi Ubuntu 26.04 LTS 7.0.0-1014.14
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-27.27.1
  • linux-nvidia Ubuntu 26.04 LTS 7.0.0-1013.13

ubuntu advisories UBUNTU-CVE-2026-46025

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source openSUSE Tumbleweed 7.0.11-1.1

opensuse advisories openSUSE-SU-2026:10954-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-46025 updated

kernel: mm/damon/core: fix damon_call() vs kdamond_fn() exit race

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.09% chance of exploitation in the next 30 days, higher than 0% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 4.7 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
Technology feeds

References

Sources

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