smb: client: fix data corruption with concurrent writes and O_TRUNC

{
  "id": "b9ad4d4bebf2bff3a840a385a05eb8c619503dc84b559cab436ddee34d3df12d",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-99111",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "smb: client: fix data corruption with concurrent writes and O_TRUNC",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: smb: client: fix data corruption with concurrent writes and O_TRUNC cifs_do_truncate() flushes dirty pages with filemap_write_and_wait() and truncates the file on the server, but in the old code both operations ran without holding i_rwsem or invalidate_lock. A concurrent buffered write via netfs_perform_write() -- which only needs i_rwsem shared -- could dirty new pages after the flush but before the local truncation, and those pages would be silently discarded by cifs_setsize() -> truncate_pagecache(). Fix by acquiring inode_lock (exclusive i_rwsem) and filemap_invalidate_lock at the top of cifs_do_truncate(), so the entire flush-truncate-resize sequence is atomic with respect to: - buffered writes (blocked by exclusive i_rwsem, since netfs_start_io_write takes i_rwsem shared), - read page faults (blocked by exclusive invalidate_lock, since filemap_fault takes it shared), - writeback collection (blocked by netfs_wb_begin/netfs_wb_end around the server truncate and local resize, since netfs_writepages also acquires the wb lock).",
    "evidence": "cve:CVE-2026-99111",
    "products": [
      {
        "name": {
          "value": "Linux",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      },
      {
        "name": {
          "value": "Linux",
          "evidence": "/containers/cna/affected/1/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-99111",
      "aliases": [
        "CVE-2026-99111"
      ],
      "metrics": [],
      "affected": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "4d143608a0445443a85c9b29f4c9f8e63d5dbfc9",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "ffa66fdc7d35b890606767c4d2c7ac26b4d90a99",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "a8603b52b39f520ea8a34def74c23fba87396d3e",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/smb/client/file.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.18",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.18.59",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.2.13",
              "versionType": "semver",
              "lessThanOrEqual": "7.2.*"
            },
            {
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "fs/smb/client/file.c"
          ],
          "defaultStatus": "affected"
        }
      ],
      "modified": "2026-10-28T10:34:29.053Z",
      "provider": "cve",
      "references": [
        "https://git.kernel.org/stable/c/4d143608a0445443a85c9b29f4c9f8e63d5dbfc9",
        "https://git.kernel.org/stable/c/ffa66fdc7d35b890606767c4d2c7ac26b4d90a99",
        "https://git.kernel.org/stable/c/a8603b52b39f520ea8a34def74c23fba87396d3e"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
          "shortName": "Linux",
          "dateUpdated": "2026-10-28T10:34:29.053Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-99111",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-cve",
  "document_id": 425348,
  "published_at": "2026-10-28T10:34:29.053+00:00"
}