CVE-2026-98214 (GCVE-0-2026-98214)
Vulnerability from cvelistv5
Published
2026-10-06 08:44
Modified
2026-10-19 09:15
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: selinux: recheck intermediate backing files on mprotect() mprotect() can be used to bypass the SELinux checks that mmap() performs against the intermediate layers of a stacked filesystem. mmap() checks every backing layer as the request descends through the stack. mprotect() only has the lowest backing file in vma->vm_file, so it rechecks the top-level user and the lowest mounter, but skips the mounters of every layer in between. With two nested overlayfs mounts and a policy denying mounter_t -> middle_file_t:file { execute }, a direct mmap(PROT_EXEC) is denied: avc: denied { execute } for pid=71 comm="nested_exec" path="/payload" dev="overlay" ino=9 scontext=user_u:base_r:mounter_t tcontext=user_u:object_r:middle_file_t tclass=file permissive=0 while mmap(PROT_NONE) followed by mprotect(PROT_EXEC) succeeds. Preserve each intermediate path, mounter SID and file-description SID in the backing-file security blob, copying the saved entries when another backing layer is opened. Allocate the array only for nested backing files, and release it and the path references in the backing_file_free hook. During mprotect(), recheck fd { use } and the requested inode permissions for every saved mounter, and include the intermediate layers in the execmod checks. Policy for nested stacking may then need to grant intermediate mounters what a direct mmap() already requires, and execmod on intermediate labels for binaries using text relocations. Tested on arm64 QEMU with a small BusyBox initramfs and a purpose-built SELinux policy, on a mainline tree containing commit f2381b546e7e ("fs: fix user path of nested backing files"). [PM: subject tweak]
References
Impacted products
Vendor Product Version
Linux Linux Version: bc6c380c1159de52a252ed11f19a42c47f60a735
Version: 8bacd09f12c27710228562e4d13163e58c5f4a45
Version: d844702198395d3f80222777030f69db6be6b709
Version: 82544d36b1729153c8aeb179e84750f0c085d3b1
Version: 82544d36b1729153c8aeb179e84750f0c085d3b1
Version: cd0e707a927a70cdfd8bc5a512a9719a87f5ed51
Version: 6.6.144   ≤
Version: 6.12.95   ≤
Version: 6.18.38   ≤
Version: 7.0.4   ≤
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{
  "containers": {
    "cna": {
      "affected": [
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          "defaultStatus": "unaffected",
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          "programFiles": [
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nselinux: recheck intermediate backing files on mprotect()\n\nmprotect() can be used to bypass the SELinux checks that mmap() performs\nagainst the intermediate layers of a stacked filesystem.\n\nmmap() checks every backing layer as the request descends through the\nstack.  mprotect() only has the lowest backing file in vma-\u003evm_file, so it\nrechecks the top-level user and the lowest mounter, but skips the mounters\nof every layer in between.  With two nested overlayfs mounts and a policy\ndenying mounter_t -\u003e middle_file_t:file { execute }, a direct\nmmap(PROT_EXEC) is denied:\n\n  avc:  denied  { execute } for  pid=71 comm=\"nested_exec\"\n    path=\"/payload\" dev=\"overlay\" ino=9\n    scontext=user_u:base_r:mounter_t\n    tcontext=user_u:object_r:middle_file_t tclass=file permissive=0\n\nwhile mmap(PROT_NONE) followed by mprotect(PROT_EXEC) succeeds.\n\nPreserve each intermediate path, mounter SID and file-description SID in\nthe backing-file security blob, copying the saved entries when another\nbacking layer is opened.  Allocate the array only for nested backing files,\nand release it and the path references in the backing_file_free hook.\n\nDuring mprotect(), recheck fd { use } and the requested inode permissions\nfor every saved mounter, and include the intermediate layers in the execmod\nchecks.  Policy for nested stacking may then need to grant intermediate\nmounters what a direct mmap() already requires, and execmod on intermediate\nlabels for binaries using text relocations.\n\nTested on arm64 QEMU with a small BusyBox initramfs and a purpose-built\nSELinux policy, on a mainline tree containing\ncommit f2381b546e7e (\"fs: fix user path of nested backing files\").\n\n[PM: subject tweak]"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:15:45.082Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/4d50ebe5a27724e020747ffd61a051dec67cb8ec"
        },
        {
          "url": "https://git.kernel.org/stable/c/89376fbfdcc1a728e1775f98752cdd90b0930a00"
        },
        {
          "url": "https://git.kernel.org/stable/c/d127c7e1f3e1231d8ac8b2738e3f00bea12afe74"
        },
        {
          "url": "https://git.kernel.org/stable/c/c2bbb905af2293549651b614a52ad91e0b462b60"
        },
        {
          "url": "https://git.kernel.org/stable/c/78fc54b934bfb2c18aad8154c7302067146946f9"
        }
      ],
      "title": "selinux: recheck intermediate backing files on mprotect()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98214",
    "datePublished": "2026-10-06T08:44:50.209Z",
    "dateReserved": "2026-09-25T10:25:14.325Z",
    "dateUpdated": "2026-10-19T09:15:45.082Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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