GHSA-2PCW-FG2M-836W

Vulnerability from github – Published: 2025-04-08 09:31 – Updated: 2025-11-03 21:33
VLAI?
Details

In the Linux kernel, the following vulnerability has been resolved:

mm/migrate: fix shmem xarray update during migration

A shmem folio can be either in page cache or in swap cache, but not at the same time. Namely, once it is in swap cache, folio->mapping should be NULL, and the folio is no longer in a shmem mapping.

In __folio_migrate_mapping(), to determine the number of xarray entries to update, folio_test_swapbacked() is used, but that conflates shmem in page cache case and shmem in swap cache case. It leads to xarray multi-index entry corruption, since it turns a sibling entry to a normal entry during xas_store() (see [1] for a userspace reproduction). Fix it by only using folio_test_swapcache() to determine whether xarray is storing swap cache entries or not to choose the right number of xarray entries to update.

[1] https://lore.kernel.org/linux-mm/Z8idPCkaJW1IChjT@casper.infradead.org/

Note: In __split_huge_page(), folio_test_anon() && folio_test_swapcache() is used to get swap_cache address space, but that ignores the shmem folio in swap cache case. It could lead to NULL pointer dereferencing when a in-swap-cache shmem folio is split at __xa_store(), since !folio_test_anon() is true and folio->mapping is NULL. But fortunately, its caller split_huge_page_to_list_to_order() bails out early with EBUSY when folio->mapping is NULL. So no need to take care of it here.

Severity ?
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2025-22015"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-04-08T09:15:26Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/migrate: fix shmem xarray update during migration\n\nA shmem folio can be either in page cache or in swap cache, but not at the\nsame time.  Namely, once it is in swap cache, folio-\u003emapping should be\nNULL, and the folio is no longer in a shmem mapping.\n\nIn __folio_migrate_mapping(), to determine the number of xarray entries to\nupdate, folio_test_swapbacked() is used, but that conflates shmem in page\ncache case and shmem in swap cache case.  It leads to xarray multi-index\nentry corruption, since it turns a sibling entry to a normal entry during\nxas_store() (see [1] for a userspace reproduction).  Fix it by only using\nfolio_test_swapcache() to determine whether xarray is storing swap cache\nentries or not to choose the right number of xarray entries to update.\n\n[1] https://lore.kernel.org/linux-mm/Z8idPCkaJW1IChjT@casper.infradead.org/\n\nNote:\nIn __split_huge_page(), folio_test_anon() \u0026\u0026 folio_test_swapcache() is\nused to get swap_cache address space, but that ignores the shmem folio in\nswap cache case.  It could lead to NULL pointer dereferencing when a\nin-swap-cache shmem folio is split at __xa_store(), since\n!folio_test_anon() is true and folio-\u003emapping is NULL.  But fortunately,\nits caller split_huge_page_to_list_to_order() bails out early with EBUSY\nwhen folio-\u003emapping is NULL.  So no need to take care of it here.",
  "id": "GHSA-2pcw-fg2m-836w",
  "modified": "2025-11-03T21:33:30Z",
  "published": "2025-04-08T09:31:12Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-22015"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/29124ae980e2860f0eec7355949d3d3292ee81da"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/49100c0b070e900f87c8fac3be9b9ef8a30fa673"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/60cf233b585cdf1f3c5e52d1225606b86acd08b0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/75cfb92eb63298d717b6b0118f91ba12c4fcfeb5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c057ee03f751d6cecf7ee64f52f6545d94082aaa"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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