{
  "threat_severity" : "Low",
  "public_date" : "2026-04-22T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: mm/huge_memory: fix folio isn't locked in softleaf_to_folio()",
    "id" : "2460685",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2460685"
  },
  "cvss3" : {
    "cvss3_base_score" : "5.5",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
    "status" : "draft"
  },
  "cwe" : "CWE-366",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nmm/huge_memory: fix folio isn't locked in softleaf_to_folio()\nOn arm64 server, we found folio that get from migration entry isn't locked\nin softleaf_to_folio().  This issue triggers when mTHP splitting and\nzap_nonpresent_ptes() races, and the root cause is lack of memory barrier\nin softleaf_to_folio().  The race is as follows:\nCPU0                                             CPU1\ndeferred_split_scan()                              zap_nonpresent_ptes()\nlock folio\nsplit_folio()\nunmap_folio()\nchange ptes to migration entries\n__split_folio_to_order()                         softleaf_to_folio()\nset flags(including PG_locked) for tail pages    folio = pfn_folio(softleaf_to_pfn(entry))\nsmp_wmb()                                        VM_WARN_ON_ONCE(!folio_test_locked(folio))\nprep_compound_page() for tail pages\nIn __split_folio_to_order(), smp_wmb() guarantees page flags of tail pages\nare visible before the tail page becomes non-compound.  smp_wmb() should\nbe paired with smp_rmb() in softleaf_to_folio(), which is missed.  As a\nresult, if zap_nonpresent_ptes() accesses migration entry that stores tail\npfn, softleaf_to_folio() may see the updated compound_head of tail page\nbefore page->flags.\nThis issue will trigger VM_WARN_ON_ONCE() in pfn_swap_entry_folio()\nbecause of the race between folio split and zap_nonpresent_ptes()\nleading to a folio incorrectly undergoing modification without a folio\nlock being held.\nThis is a BUG_ON() before commit 93976a20345b (\"mm: eliminate further\nswapops predicates\"), which in merged in v6.19-rc1.\nTo fix it, add missing smp_rmb() if the softleaf entry is migration entry\nin softleaf_to_folio() and softleaf_to_page().\n[tujinjiang@huawei.com: update function name and comments]", "A flaw was found in the Linux kernel. A race condition exists in the memory management subsystem, specifically during transparent huge page (THP) splitting and page table entry invalidation. This can occur when a memory folio (a unit of memory) is accessed and modified without proper locking due to a missing memory barrier. This can lead to a kernel warning and potentially a system crash, resulting in a Denial of Service." ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-31466\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31466\nhttps://lore.kernel.org/linux-cve-announce/2026042253-CVE-2026-31466-4fba@gregkh/T" ],
  "name" : "CVE-2026-31466",
  "csaw" : false
}