FKIE_CVE-2026-64142

Vulnerability from fkie_nvd - Published: 2026-07-19 16:17 - Updated: 2026-07-20 15:17
Severity
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: close durable scavenger races against m_fp_list lookups ksmbd_durable_scavenger() has two related races against any walker that iterates f_ci->m_fp_list, including ksmbd_lookup_fd_inode() (used by ksmbd_vfs_rename) and the share-mode checks in fs/smb/server/smb_common.c. (1) fp->node list-head reuse. Durable-preserved handles can remain linked on f_ci->m_fp_list after session teardown so share-mode checks still see them while the handle is reconnectable. The scavenger collected expired handles by adding fp->node to a local scavenger_list after removing them from the global durable idr. Because fp->node is the same list_head used by m_fp_list, list_add(&fp->node, &scavenger_list) overwrites the m_fp_list links and corrupts both lists. CONFIG_DEBUG_LIST can report this on the share-mode walk path. (2) Refcount race against m_fp_list walkers. The scavenger qualifies an expired durable handle with atomic_read(&fp->refcount) > 1 and fp->conn under global_ft.lock, removes fp from global_ft, then drops global_ft.lock before unlinking fp from m_fp_list and freeing it. During that gap fp is still linked on m_fp_list with f_state == FP_INITED. ksmbd_lookup_fd_inode() under m_lock read calls ksmbd_fp_get() (atomic_inc_not_zero on refcount that is still 1) and takes a live reference; the scavenger then unlinks and frees fp while the holder owns a reference, leading to UAF on the holder's subsequent ksmbd_fd_put() and on any field reads performed by a concurrent share-mode walker that iterates m_fp_list without taking ksmbd_fp_get() (smb_check_perm_dleases-like paths). Fix both: * Stop reusing fp->node as a scavenger-private list node. Remove one expired handle from global_ft under global_ft.lock, take an explicit transient reference, drop the lock, unlink fp->node from m_fp_list under f_ci->m_lock, then drop both the durable lifetime and transient references with atomic_sub_and_test(2, &fp->refcount). If the scavenger is the last putter the close runs there; otherwise an in-flight holder that already raced through the m_fp_list lookup owns the final close via its ksmbd_fd_put() path. The one-at-a-time disposal can rescan the durable idr when multiple handles expire in the same pass, but durable scavenging is a background expiration path and the final full scan recomputes min_timeout before the next wait. * Clear fp->persistent_id inside __ksmbd_remove_durable_fd() right after idr_remove(), so a delayed final close from a holder that snatched fp does not re-issue idr_remove() on a persistent id that idr_alloc_cyclic() in ksmbd_open_durable_fd() may have already handed out to a brand-new durable handle. * Bypass the per-conn open_files_count decrement in __put_fd_final() when fp is detached from any session table (fp->conn cleared by session_fd_check() at durable preserve -- paired with the volatile_id clear at unpublish, so checking fp->conn alone is sufficient). The walker that owns the final close runs from an unrelated work->conn whose stats.open_files_count never tracked this durable fp; without this guard the holder would underflow that unrelated counter. The two races are folded into one patch because patch (1) alone cleans up the corrupted list but leaves a deterministic UAF window for m_fp_list walkers that the transient-reference and persistent_id discipline in (2) close; bisecting onto an intermediate state would land on a UAF that pre-patch chaos merely made less reproducible. Validation: * CONFIG_DEBUG_LIST coverage for the list_head reuse path. * KASAN-enabled direct SMB2 durable-handle coverage that exercised ksmbd_durable_scavenger() and non-NULL ksmbd_lookup_fd_inode() returns while durable handles expired under concurrent rename lookups, with no KASAN, UAF, list-corruption, ODEBUG, or WARNING reports. ---truncated---
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1f8f3246d55f89350a1a67bdf3744b7241048e4e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3a436932eb397e909d0607d76a8325abd9d85a35
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5da69a65b282d2276de22e5194ba0f88c836170c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/95f072ef934ca00711d510676b8792cbf59a5aae
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/bf736184d063da1a552ffeff0481813599a182cc
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/vfs_cache.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3a436932eb397e909d0607d76a8325abd9d85a35",
              "status": "affected",
              "version": "7f0cb478703cbeaddfe5c9101c5c73cd975d1073",
              "versionType": "git"
            },
            {
              "lessThan": "95f072ef934ca00711d510676b8792cbf59a5aae",
              "status": "affected",
              "version": "d484d621d40f4a8b8959008802d79bef3609641b",
              "versionType": "git"
            },
            {
              "lessThan": "5da69a65b282d2276de22e5194ba0f88c836170c",
              "status": "affected",
              "version": "d484d621d40f4a8b8959008802d79bef3609641b",
              "versionType": "git"
            },
            {
              "lessThan": "1f8f3246d55f89350a1a67bdf3744b7241048e4e",
              "status": "affected",
              "version": "d484d621d40f4a8b8959008802d79bef3609641b",
              "versionType": "git"
            },
            {
              "lessThan": "bf736184d063da1a552ffeff0481813599a182cc",
              "status": "affected",
              "version": "d484d621d40f4a8b8959008802d79bef3609641b",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/vfs_cache.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.11"
            },
            {
              "lessThan": "6.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.92",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.34",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: close durable scavenger races against m_fp_list lookups\n\nksmbd_durable_scavenger() has two related races against any walker\nthat iterates f_ci-\u003em_fp_list, including ksmbd_lookup_fd_inode()\n(used by ksmbd_vfs_rename) and the share-mode checks in\nfs/smb/server/smb_common.c.\n\n(1) fp-\u003enode list-head reuse.  Durable-preserved handles can remain\nlinked on f_ci-\u003em_fp_list after session teardown so share-mode checks\nstill see them while the handle is reconnectable.  The scavenger\ncollected expired handles by adding fp-\u003enode to a local\nscavenger_list after removing them from the global durable idr.\nBecause fp-\u003enode is the same list_head used by m_fp_list,\nlist_add(\u0026fp-\u003enode, \u0026scavenger_list) overwrites the m_fp_list links\nand corrupts both lists.  CONFIG_DEBUG_LIST can report this on the\nshare-mode walk path.\n\n(2) Refcount race against m_fp_list walkers.  The scavenger qualifies\nan expired durable handle with atomic_read(\u0026fp-\u003erefcount) \u003e 1 and\nfp-\u003econn under global_ft.lock, removes fp from global_ft, then drops\nglobal_ft.lock before unlinking fp from m_fp_list and freeing it.\nDuring that gap fp is still linked on m_fp_list with f_state ==\nFP_INITED.  ksmbd_lookup_fd_inode() under m_lock read calls\nksmbd_fp_get() (atomic_inc_not_zero on refcount that is still 1) and\ntakes a live reference; the scavenger then unlinks and frees fp\nwhile the holder owns a reference, leading to UAF on the holder\u0027s\nsubsequent ksmbd_fd_put() and on any field reads performed by a\nconcurrent share-mode walker that iterates m_fp_list without taking\nksmbd_fp_get() (smb_check_perm_dleases-like paths).\n\nFix both:\n\n  * Stop reusing fp-\u003enode as a scavenger-private list node.  Remove\n    one expired handle from global_ft under global_ft.lock, take an\n    explicit transient reference, drop the lock, unlink fp-\u003enode\n    from m_fp_list under f_ci-\u003em_lock, then drop both the durable\n    lifetime and transient references with atomic_sub_and_test(2,\n    \u0026fp-\u003erefcount).  If the scavenger is the last putter the close\n    runs there; otherwise an in-flight holder that already raced\n    through the m_fp_list lookup owns the final close via its\n    ksmbd_fd_put() path.  The one-at-a-time disposal can rescan the\n    durable idr when multiple handles expire in the same pass, but\n    durable scavenging is a background expiration path and the final\n    full scan recomputes min_timeout before the next wait.\n\n  * Clear fp-\u003epersistent_id inside __ksmbd_remove_durable_fd() right\n    after idr_remove(), so a delayed final close from a holder that\n    snatched fp does not re-issue idr_remove() on a persistent id\n    that idr_alloc_cyclic() in ksmbd_open_durable_fd() may have\n    already handed out to a brand-new durable handle.\n\n  * Bypass the per-conn open_files_count decrement in\n    __put_fd_final() when fp is detached from any session table\n    (fp-\u003econn cleared by session_fd_check() at durable preserve --\n    paired with the volatile_id clear at unpublish, so checking\n    fp-\u003econn alone is sufficient).  The walker that owns the final\n    close runs from an unrelated work-\u003econn whose\n    stats.open_files_count never tracked this durable fp; without\n    this guard the holder would underflow that unrelated counter.\n\nThe two races are folded into one patch because patch (1) alone\ncleans up the corrupted list but leaves a deterministic UAF window\nfor m_fp_list walkers that the transient-reference and\npersistent_id discipline in (2) close; bisecting onto an\nintermediate state would land on a UAF that pre-patch chaos merely\nmade less reproducible.\n\nValidation:\n  * CONFIG_DEBUG_LIST coverage for the list_head reuse path.\n  * KASAN-enabled direct SMB2 durable-handle coverage that exercised\n    ksmbd_durable_scavenger() and non-NULL ksmbd_lookup_fd_inode()\n    returns while durable handles expired under concurrent rename\n    lookups, with no KASAN, UAF, list-corruption, ODEBUG, or WARNING\n    reports.\n---truncated---"
    }
  ],
  "id": "CVE-2026-64142",
  "lastModified": "2026-07-20T15:17:12.280",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T16:17:56.103",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1f8f3246d55f89350a1a67bdf3744b7241048e4e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3a436932eb397e909d0607d76a8325abd9d85a35"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5da69a65b282d2276de22e5194ba0f88c836170c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/95f072ef934ca00711d510676b8792cbf59a5aae"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/bf736184d063da1a552ffeff0481813599a182cc"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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