mm: mglru: fix stale batch updates after memcg reparenting

{
  "id": "d62b2871c4c4707ea420ee8ddaf56760a080990140bc788abfc942dba91a49f1",
  "url": "https://osv.dev/vulnerability/CVE-2026-80719",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mm: mglru: fix stale batch updates after memcg reparenting",
    "summary": "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.",
    "evidence": "osv:CVE-2026-80719",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.1.8",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-80719",
      "aliases": [
        "CVE-2026-80719"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "f304652609eae3814b0e9d11c75c0e0cb62da31f"
                },
                {
                  "fixed": "fceb6b7f3ddec6ea9fc11577f4cf1b2da73a3101"
                },
                {
                  "fixed": "de4660898b7aa7e03d3b120a6bfa6b26211e4e77"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80719.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.1.0"
                },
                {
                  "fixed": "7.1.8"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80719.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:27.969053359Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/de4660898b7aa7e03d3b120a6bfa6b26211e4e77",
        "https://git.kernel.org/stable/c/fceb6b7f3ddec6ea9fc11577f4cf1b2da73a3101",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80719.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-80719",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80719.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-80719",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 494831,
  "published_at": "2026-08-28T06:53:16.087+00:00"
}