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

mm: mglru: fix stale batch updates after memcg reparenting

The mglru page table walker batches per-generation size deltas in
walk->nr_pages while walking page tables without holding the lruvec lock.
The reset_batch_size() later folds those deltas into walk->lruvec under
the lruvec lock.

The page table walker can run concurrently with the memcg reparenting path
as follows:

CPU0 CPU1
==== ====

walk_mm
--> walk_page_range
--> update_batch_size
--> walk->nr_pages += delta

mem_cgroup_css_offline
--> memcg_reparent_objcgs
--> lock lruvec
lru_gen_reparent_memcg
--> reparent child folios to parent
unlock lruvec

lock lruvec
reset_batch_size
--> child lrugen->nr_pages += delta

This will trigger the following warning in lru_gen_exit_memcg():

VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
sizeof(lruvec->lrugen.nr_pages)));

And the user-visible impact of underestimated nr_pages in MGLRU was
premature OOMs because MGLRU does not try to reclaim memory when nr_pages
reaches zero, but there are still more pages.

To fix it, make reset_batch_size() check CSS_DYING under RCU before
flushing the pending batch. A non-dying memcg keeps the original lruvec
stable against RCU-delayed offlining; a dying memcg redirects the deltas
to the first non-dying ancestor.
Published: 2026-08-28
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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History

Fri, 28 Aug 2026 11:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-400

Fri, 28 Aug 2026 07:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: mm: mglru: fix stale batch updates after memcg reparenting The mglru page table walker batches per-generation size deltas in walk->nr_pages while walking page tables without holding the lruvec lock. The reset_batch_size() later folds those deltas into walk->lruvec under the lruvec lock. The page table walker can run concurrently with the memcg reparenting path as follows: CPU0 CPU1 ==== ==== walk_mm --> walk_page_range --> update_batch_size --> walk->nr_pages += delta mem_cgroup_css_offline --> memcg_reparent_objcgs --> lock lruvec lru_gen_reparent_memcg --> reparent child folios to parent unlock lruvec lock lruvec reset_batch_size --> child lrugen->nr_pages += delta This will trigger the following warning in lru_gen_exit_memcg(): VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0, sizeof(lruvec->lrugen.nr_pages))); And the user-visible impact of underestimated nr_pages in MGLRU was premature OOMs because MGLRU does not try to reclaim memory when nr_pages reaches zero, but there are still more pages. To fix it, make reset_batch_size() check CSS_DYING under RCU before flushing the pending batch. A non-dying memcg keeps the original lruvec stable against RCU-delayed offlining; a dying memcg redirects the deltas to the first non-dying ancestor.
Title mm: mglru: fix stale batch updates after memcg reparenting
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-28T06:53:16.087Z

Reserved: 2026-08-26T14:34:25.788Z

Link: CVE-2026-80719

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-28T08:16:57.720

Modified: 2026-08-28T08:16:57.720

Link: CVE-2026-80719

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-28T11:00:11Z

Weaknesses
  • CWE-400

    Uncontrolled Resource Consumption