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NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with list_for_each_entry_safe(ni, tmp, ...). For each expired entry it sets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the source vfsmount, then reacquires the lock to list_del + kfree the entry and continue iterating via the macro's saved tmp pointer. The nsui_busy flag protects the current ni from concurrent nfsd4_ssc_setup_dul() finders during the lock-drop window, but it does not pin tmp. Another nfsd RPC thread that fails its source- server mount and reaches nfsd4_ssc_cancel_dul() will, during that same window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount item, and release the lock. If that item is the saved tmp of the expire walk, the next iteration dereferences a freed nfsd4_ssc_umount_item. Restart the walk from the head after the mntput() unlock window so no saved next pointer survives the lock-drop. The list is bounded by the number of active inter-server source mounts (typically small) and the expire delayed-work runs periodically rather than per-IO, so the restart is cheap.

Announced Group revision 1
Original source ↗

CVE-2026-89712

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-89712

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "a4bc287943f5695209ff36bdc89f17b48d68fae7",
        "lessThan": "2b59029b8f24a99b5d844af2da3950d39d36eeea",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
        "lessThan": "d9e151fea5ed706c1284adacabd869b0be745db2",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
        "lessThan": "659ee3da073164e1e6e40dfcbc26eeed85845f93",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
        "lessThan": "60680ae7243b22de3d09be990d8e23bcfc4af837",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
        "lessThan": "77de363d9a1c8cd35f20482782c612cda085791a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
        "lessThan": "4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
        "lessThan": "7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "f4e44b393389c77958f7c58bf4415032b4cda15b",
        "lessThan": "036c1b182f4da65363e79ec0ac276edc6b7296e5",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "5.10.220",
        "lessThan": "5.10.270",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "fs/nfsd/nfs4state.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.14"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.14",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.270",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.221",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.188",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.157",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.109",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.50",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.4",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/nfsd/nfs4state.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-89712

Source reference: /cveMetadata/cveId

Publisher severity

critical

Source reference: /containers/cna/metrics

Event
#35193 · Revision 1
Added to Heist Feed
Publisher date
Read the original announcement

Revision history

  1. CVE-2026-89712 · Revision 1Source updated