mm: mglru: fix stale batch updates after memcg reparenting

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80719
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-28 08:16:57 UTC
Updated2026-08-28 08:16:57 UTC
DescriptionIn 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.

Risk And Classification

EPSS: 0.001450000 probability, percentile 0.040620000 (date 2026-08-30)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected f304652609eae3814b0e9d11c75c0e0cb62da31f fceb6b7f3ddec6ea9fc11577f4cf1b2da73a3101 git Not specified
CNA Linux Linux affected f304652609eae3814b0e9d11c75c0e0cb62da31f de4660898b7aa7e03d3b120a6bfa6b26211e4e77 git Not specified
CNA Linux Linux affected 7.1 Not specified
CNA Linux Linux unaffected 7.1 semver Not specified
CNA Linux Linux unaffected 7.1.8 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/de4660898b7aa7e03d3b120a6bfa6b26211e4e77 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fceb6b7f3ddec6ea9fc11577f4cf1b2da73a3101 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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