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fs: fix user path of nested backing files

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: fs: fix user path of nested backing files backing_file_open() derives the path to be stored in the new backing file from user_file->f_path. This is incorrect when user_file itself is a backing file, which is the case for nested stacking filesystems, e.g. overlayfs mounts where the lowerdir of one overlayfs is the merged directory of another. Since commit def3ae83da02 ("fs: store real path instead of fake path in backing file f_path") the f_path of a backing file holds the real path of the intermediate layer, not the path that the user opened. Commit 924577e4f6ca ("ovl: Fix nested backing file paths") fixed this for such configurations by passing file_user_path() from ovl_open_realfile(). However, commit 6af36aeb147a ("lsm: add backing_file LSM hooks") changed the first argument of backing_file_open() from the user path back to the user file and derived the path from user_file->f_path again, silently re-introducing the problem. As a result, files mapped through a nested overlayfs show the wrong path in /proc//maps and in perf/ftrace mmap records. For example, with two nested overlayfs mounts: mkdir -p /ovl/{lower,upper,work,merged} /ovl/nested echo hello > /ovl/lower/foo mount -t overlay overlay \ -o lowerdir=/ovl/lower,upperdir=/ovl/upper,workdir=/ovl/work \ /ovl/merged # at least two lowerdirs are needed when upperdir is nonexistent mount -t overlay overlay \ -o lowerdir=/ovl/merged:/ovl/lower /ovl/nested ma

Announced Source revision 1
Original source ↗

CVE-2026-89768

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-2026-89768

Linux

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

Affected versions
Not stated in this record
Fixed versions
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Prerequisites
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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": "5b6aa9a843205da92d860e5011a7b29062a76b8f",
        "lessThan": "88c927a63dc717b6d46b20fe13ea713916e49089",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "5dfcb15974e7d0f96aca278dd9f1b85df91523ef",
        "lessThan": "c03114634d342648bd34910aa8fb88007e92cc3c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "6af36aeb147a06dea47c49859cd6ca5659aeb987",
        "lessThan": "a35cc21355734e1acb89973d9be90ca8e4c3ed2f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "6af36aeb147a06dea47c49859cd6ca5659aeb987",
        "lessThan": "f2381b546e7e6a35c9fcee0d0ccb6c042a9aeb5d",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "41c5b269af8b1f0bffcab7766a793f294ae6764e",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "27e795afba0018b0ea9460dbad4bd706d1ba5ee0",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "6.12.95",
        "lessThan": "6.12.109",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.18.38",
        "lessThan": "6.18.50",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.6.144",
        "lessThan": "6.7",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "7.0.4",
        "lessThan": "7.1",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "fs/backing-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": "7.1"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "7.1",
        "versionType": "semver"
      },
      {
        "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/backing-file.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-89768

Source reference: /cveMetadata/cveId

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Event
#35236 · Revision 1
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