{"id":"CVE-2026-31466","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: fix folio isn't locked in softleaf_to_folio()\n\nOn arm64 server, we found folio that get from migration entry isn't locked\nin softleaf_to_folio()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: fix folio isn't locked in softleaf_to_folio()\n\nOn arm64 server, we found folio that get from migration entry isn't locked\nin softleaf_to_folio().  This …","severity":"medium","cvss":4.7,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-362"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 4.5, < 5.10.253","linux_kernel >= 5.11, < 5.15.203","linux_kernel >= 5.16, < 6.1.168","linux_kernel >= 6.2, < 6.6.134","linux_kernel >= 6.7, < 6.12.81","linux_kernel >= 6.13, < 6.18.21","linux_kernel >= 6.19, < 6.19.11","linux_kernel = 7.0"],"patched":["linux_kernel 6.19.11"],"published":"2026-04-22","updated":"2026-10-15","sourceUpdated":"2026-10-15T02:19:07.180","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-31466","references":[{"url":"https://git.kernel.org/stable/c/426ee10711586617da869c8bb798214965337617","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4c5e7f0fcd592801c9cc18f29f80fbee84eb8669","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/722cfaf6b31d31123439e67b5deac6b1261a3dea","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/7ad1997b9bc8032603df8f091761114479285769","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/7ddcf4a245c1c5a91fdd9698757e3d95179ffe41","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8bfb8414e9f2ce6f5f2f0e3d0da52f2d132128e7","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b8c49ad888892ad7b77062b9c102b799a3e9b4f8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f1acf5887c2bbaf998dc3fe32c72b7a8b84a3ddd","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00094,"epssPercentile":0.00569,"ingestedAt":"2026-09-08T15:33:26.990Z","slug":"CVE-2026-31466","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: fix folio isn't locked in softleaf_to_folio()\n\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:\n\n\tCPU0                                             CPU1\n\ndeferred_split_scan()                              zap_nonpresent_ptes()\n  lock folio\n  split_folio()\n    unmap_folio()\n      change ptes to migration entries\n    __split_folio_to_order()                         softleaf_to_folio()\n      set flags(including PG_locked) for tail pages    folio = pfn_folio(softleaf_to_pfn(entry))\n      smp_wmb()                                        VM_WARN_ON_ONCE(!folio_test_locked(folio))\n      prep_compound_page() for tail pages\n\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.\n\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.\n\nThis is a BUG_ON() before commit 93976a20345b (\"mm: eliminate further\nswapops predicates\"), which in merged in v6.19-rc1.\n\nTo fix it, add missing smp_rmb() if the softleaf entry is migration entry\nin softleaf_to_folio() and softleaf_to_page().\n\n[tujinjiang@huawei.com: update function name and comments]\n\n## Affected\n\n- `linux_kernel >= 4.5, < 5.10.253`\n- `linux_kernel >= 5.11, < 5.15.203`\n- `linux_kernel >= 5.16, < 6.1.168`\n- `linux_kernel >= 6.2, < 6.6.134`\n- `linux_kernel >= 6.7, < 6.12.81`\n- `linux_kernel >= 6.13, < 6.18.21`\n- `linux_kernel >= 6.19, < 6.19.11`\n- `linux_kernel = 7.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.19.11`","depth":"sunlit","depthScore":26,"depthScoreParts":{"impact":25.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":221713,"id":"CVE-2026-31466","ts":1792035333825,"field":"cvss","old":null,"new":"4.7"},{"seq":221712,"id":"CVE-2026-31466","ts":1792035333825,"field":"severity","old":"none","new":"medium"}]}