{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  memcg: move LRU size accounting on reparenting instead of copying it  When a memory cgroup is offlined its LRU folios are reparented to the parent.  lruvec_reparent_lru() splices the child's lists into the parent's and credits the parent with the child's per-zone lru_zone_size[], but never clears the child's copy, so the size is copied rather than moved.  lru_gen_reparent_memcg() does the same for MGLRU.  The parent is left correct, credited with exactly the folios it took over.  The stale value sits on the child and nothing will correct it: folio-\u003ememcg_data now resolves to the parent, so every later update_lru_size() for those folios goes there.  Dying cgroups are not freed immediately and mem_cgroup_iter() still walks them, so shrink_lruvec() keeps being called on them. get_scan_count() reads the phantom counter through lruvec_lru_size() and the scan loop then grinds through nr[] in SWAP_CLUSTER_MAX steps against an empty list, for as long as the dead cgroup lives.  Under MGLRU the MGLRU scanner runs instead, but count_shadow_nodes() sums all of NR_LRU_LISTS through lruvec_lru_size() and over-budgets the shadow node limit just the same.  On one 251 GiB host a sweep of every mz-\u003elru_zone_size[] found 380 counters describing folios on no list at all: 124777314 pages, 476 GiB, 1.89x the machine's RAM, across 57 cgroups.  All were on memcgs with CSS_DYING set and CSS_ONLINE clear, and parent/child pairs reported byte-identical sizes.  LRU_UNEVICTABLE needs its size moved too.  Its list is deliberately not spliced because lruvec_init() poisons the head - the unevictable LRU is imaginary and folios are never threaded on it - but the size is kept by lruvec_add_folio()/lruvec_del_folio() and those folios account to the parent from here on.  This depends on commit bf4ade7dbd76 (\"memcg: keep folio's objcg same as its node\") and must not be backported ahead of it.  Without that invariant a folio's objcg can belong to another node, so a folio already spliced onto the parent's list can still resolve to the child's lruvec until the objcg's node is reparented in a later iteration of memcg_reparent_objcgs(); clearing the child's counter early then lets lruvec_del_folio() underflow it and trip the WARN_ONCE()/VM_BUG_ON() in mem_cgroup_update_lru_size().",
  "id": "DEBIAN-CVE-2026-93197",
  "modified": "2026-09-18T04:47:39.094073813Z",
  "published": "2026-09-17T17:18:15.990Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-93197"
    }
  ],
  "upstream": [
    "CVE-2026-93197"
  ]
}