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selinux: preserve user SID across nested backing files

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: selinux: preserve user SID across nested backing files SELinux saves the user file SID in a backing-file security blob so it remains available after mmap() replaces vma->vm_file with a backing file. For nested backing files (overlayfs over overlayfs, or FUSE passthrough backed by overlayfs), user_file may itself be a backing file. Its fsec->sid is the SID of the mounter that opened it, rather than the user that opened the top-level file. mprotect() then checks fd { use } against the mounter SID. This can incorrectly deny access without a domain transition, or check the wrong target SID after one. Copy the saved user SID when user_file is a backing file. Keep using the regular file SID for the first backing layer. With two nested overlayfs mounts and SELinux enforcing, mprotect(PROT_READ) returns EACCES with an fd { use } denial against the mounter SID. With this change, mprotect() succeeds. Tested on arm64 QEMU with a small BusyBox initramfs and a purpose-built SELinux policy. The original test was also repeated with Fedora Cloud Base 44 userspace and gave the same result.

Announced Source revision 1
Original source ↗

CVE-2026-98215

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-2026-98215

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": "bc6c380c1159de52a252ed11f19a42c47f60a735",
        "lessThan": "caa1b913d90d5dc07073733326d2af0f0288f089",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8bacd09f12c27710228562e4d13163e58c5f4a45",
        "lessThan": "6aaeec59aadcd1eafc18b049f1b759fb6b9d9569",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "d844702198395d3f80222777030f69db6be6b709",
        "lessThan": "9d99b770e7b67b00bdef9005b928aad13e1d679b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "82544d36b1729153c8aeb179e84750f0c085d3b1",
        "lessThan": "ff20d16b2e8230c034e21540043df47222dcc09b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "82544d36b1729153c8aeb179e84750f0c085d3b1",
        "lessThan": "8c0c602202b9a4909b00bc3354e3c0355bc69e65",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "cd0e707a927a70cdfd8bc5a512a9719a87f5ed51",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "6.6.144",
        "lessThan": "6.6.158",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.12.95",
        "lessThan": "6.12.112",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.18.38",
        "lessThan": "6.18.54",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "7.0.4",
        "lessThan": "7.1",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "security/selinux/hooks.c",
      "security/selinux/include/objsec.h"
    ],
    "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": "6.6.158",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.112",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.54",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.8",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "security/selinux/hooks.c",
      "security/selinux/include/objsec.h"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-98215

Source reference: /cveMetadata/cveId

Publisher severity

No explicit severity was provided.

Event
#38297 · Revision 1
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