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MEDIUM

mm: memcg: stop reclaim when a limit update is superseded

Published Sep 11, 2026

Description

kernfs serializes file operations only per open file, so separate open files can update the same memory.high or memory.max file concurrently. Both handlers store the new limit before synchronous reclaim, but continue to use the writer's local target in the reclaim loop. If another writer raises or removes the limit, the first writer can continue reclaiming toward a stale target.

For memory.max, this can leave the writer looping indefinitely once reclaim retries are exhausted. The OOM path sees sufficient margin under the current limit and returns true without killing, while the writer still compares usage against its stale target and records another OOM event.

Check the current limit at the start of each reclaim iteration and stop if it no longer matches the writer's target.

Reproducer:

Populate a cgroup with anonymous memory and disable swapping. Lower memory.max from one open file, then restore it to "max" through another open file after the new limit becomes visible.

Without the patch, the first writer remains blocked and repeatedly increments the OOM event counter. With the patch, it returns normally.

This was not motivated by a reported production workload. We found it through automated randomized testing for our cgroup observability work and reduced it to the reproducer above.

Affected products

Remediation

No remediation recorded yet.

Weaknesses (1)

CWE-367

References (13)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner Linux
Published Sep 11, 2026
Updated Sep 14, 2026
Reserved Sep 11, 2026
Link CVE-2026-89752
CISA Vulnrichment
Updated n/a
NVD
Status Received
Modified Sep 14, 2026
Link CVE-2026-89752
Red Hat
Severity Low
Public date Sep 11, 2026
Links CVE-2026-89752 - Bugzilla