CVE-2026-23161 (GCVE-0-2026-23161)

Vulnerability from cvelistv5 – Published: 2026-02-14 16:01 – Updated: 2026-02-14 16:01
VLAI?
Title
mm/shmem, swap: fix race of truncate and swap entry split
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/shmem, swap: fix race of truncate and swap entry split The helper for shmem swap freeing is not handling the order of swap entries correctly. It uses xa_cmpxchg_irq to erase the swap entry, but it gets the entry order before that using xa_get_order without lock protection, and it may get an outdated order value if the entry is split or changed in other ways after the xa_get_order and before the xa_cmpxchg_irq. And besides, the order could grow and be larger than expected, and cause truncation to erase data beyond the end border. For example, if the target entry and following entries are swapped in or freed, then a large folio was added in place and swapped out, using the same entry, the xa_cmpxchg_irq will still succeed, it's very unlikely to happen though. To fix that, open code the Xarray cmpxchg and put the order retrieval and value checking in the same critical section. Also, ensure the order won't exceed the end border, skip it if the entry goes across the border. Skipping large swap entries crosses the end border is safe here. Shmem truncate iterates the range twice, in the first iteration, find_lock_entries already filtered such entries, and shmem will swapin the entries that cross the end border and partially truncate the folio (split the folio or at least zero part of it). So in the second loop here, if we see a swap entry that crosses the end order, it must at least have its content erased already. I observed random swapoff hangs and kernel panics when stress testing ZSWAP with shmem. After applying this patch, all problems are gone.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 809bc86517cc408b5b8cb8e08e69096639432bc8 , < a99f9a4669a04662c8f9efe0e62cafc598153139 (git)
Affected: 809bc86517cc408b5b8cb8e08e69096639432bc8 , < b23bee8cdb7aabce5701a7f57414db5a354ae8ed (git)
Affected: 809bc86517cc408b5b8cb8e08e69096639432bc8 , < 8a1968bd997f45a9b11aefeabdd1232e1b6c7184 (git)
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    Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.69 , ≤ 6.12.* (semver)
Unaffected: 6.18.9 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/shmem.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "versionType": "git"
            },
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          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "6.12"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
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              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.9",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.69",
                  "versionStartIncluding": "6.12",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.18.9",
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                },
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                  "versionEndExcluding": "6.19",
                  "versionStartIncluding": "6.12",
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/shmem, swap: fix race of truncate and swap entry split\n\nThe helper for shmem swap freeing is not handling the order of swap\nentries correctly.  It uses xa_cmpxchg_irq to erase the swap entry, but it\ngets the entry order before that using xa_get_order without lock\nprotection, and it may get an outdated order value if the entry is split\nor changed in other ways after the xa_get_order and before the\nxa_cmpxchg_irq.\n\nAnd besides, the order could grow and be larger than expected, and cause\ntruncation to erase data beyond the end border.  For example, if the\ntarget entry and following entries are swapped in or freed, then a large\nfolio was added in place and swapped out, using the same entry, the\nxa_cmpxchg_irq will still succeed, it\u0027s very unlikely to happen though.\n\nTo fix that, open code the Xarray cmpxchg and put the order retrieval and\nvalue checking in the same critical section.  Also, ensure the order won\u0027t\nexceed the end border, skip it if the entry goes across the border.\n\nSkipping large swap entries crosses the end border is safe here.  Shmem\ntruncate iterates the range twice, in the first iteration,\nfind_lock_entries already filtered such entries, and shmem will swapin the\nentries that cross the end border and partially truncate the folio (split\nthe folio or at least zero part of it).  So in the second loop here, if we\nsee a swap entry that crosses the end order, it must at least have its\ncontent erased already.\n\nI observed random swapoff hangs and kernel panics when stress testing\nZSWAP with shmem.  After applying this patch, all problems are gone."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-14T16:01:26.569Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a99f9a4669a04662c8f9efe0e62cafc598153139"
        },
        {
          "url": "https://git.kernel.org/stable/c/b23bee8cdb7aabce5701a7f57414db5a354ae8ed"
        },
        {
          "url": "https://git.kernel.org/stable/c/8a1968bd997f45a9b11aefeabdd1232e1b6c7184"
        }
      ],
      "title": "mm/shmem, swap: fix race of truncate and swap entry split",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-23161",
    "datePublished": "2026-02-14T16:01:26.569Z",
    "dateReserved": "2026-01-13T15:37:45.979Z",
    "dateUpdated": "2026-02-14T16:01:26.569Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23161\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-02-14T16:15:56.277\",\"lastModified\":\"2026-02-14T16:15:56.277\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nmm/shmem, swap: fix race of truncate and swap entry split\\n\\nThe helper for shmem swap freeing is not handling the order of swap\\nentries correctly.  It uses xa_cmpxchg_irq to erase the swap entry, but it\\ngets the entry order before that using xa_get_order without lock\\nprotection, and it may get an outdated order value if the entry is split\\nor changed in other ways after the xa_get_order and before the\\nxa_cmpxchg_irq.\\n\\nAnd besides, the order could grow and be larger than expected, and cause\\ntruncation to erase data beyond the end border.  For example, if the\\ntarget entry and following entries are swapped in or freed, then a large\\nfolio was added in place and swapped out, using the same entry, the\\nxa_cmpxchg_irq will still succeed, it\u0027s very unlikely to happen though.\\n\\nTo fix that, open code the Xarray cmpxchg and put the order retrieval and\\nvalue checking in the same critical section.  Also, ensure the order won\u0027t\\nexceed the end border, skip it if the entry goes across the border.\\n\\nSkipping large swap entries crosses the end border is safe here.  Shmem\\ntruncate iterates the range twice, in the first iteration,\\nfind_lock_entries already filtered such entries, and shmem will swapin the\\nentries that cross the end border and partially truncate the folio (split\\nthe folio or at least zero part of it).  So in the second loop here, if we\\nsee a swap entry that crosses the end order, it must at least have its\\ncontent erased already.\\n\\nI observed random swapoff hangs and kernel panics when stress testing\\nZSWAP with shmem.  After applying this patch, all problems are gone.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/8a1968bd997f45a9b11aefeabdd1232e1b6c7184\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a99f9a4669a04662c8f9efe0e62cafc598153139\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b23bee8cdb7aabce5701a7f57414db5a354ae8ed\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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