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ext4: handle wraparound when searching for blocks for indirect mapped blocks

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: ext4: handle wraparound when searching for blocks for indirect mapped blocks Commit 4865c768b563 ("ext4: always allocate blocks only from groups inode can use") restricts what blocks will be allocated for indirect block based files to block numbers that fit within 32-bit block numbers. However, when using a review bot running on the latest Gemini LLM to check this commit when backporting into an LTS based kernel, it raised this concern: If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal group was populated via stream allocation from s_mb_last_groups), then start will be >= ngroups. Does this allow allocating blocks beyond the 32-bit limit for indirect block mapped files? The commit message mentions that ext4_mb_scan_groups_linear() takes care to not select unsupported groups. However, its loop uses group = *start, and the very first iteration will call ext4_mb_scan_group() with this unsupported group because next_linear_group() is only called at the end of the iteration. After reviewing the code paths involved and considering the LLM review, I determined that this can happen when there is a file system where some files/directories are extent-mapped and others are indirect-block mapped. To address this, add a safety clamp in ext4_mb_scan_groups().

Announced Source revision 1
Original source ↗

CVE-2026-43067

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-2026-43067

Linux

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

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
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": "9d89b9d55e25cb340c5b4b769876edc551b7a9ff",
        "lessThan": "f89bba144938921a2249237ad04a0183ff3f8930",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1b0edd6022a3f44ce87fea9959a9310f4628fbea",
        "lessThan": "83170a05908b6cf2fb3235d3065bf613ff866f3c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9eea2f57d11b30049ff996ac3eff6e0dc8089e5f",
        "lessThan": "4bec4a498ce86314d470ae6144120461f2138c29",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "34c803edc0b3365a42efcf9815acab63b4cf54e0",
        "lessThan": "12624c5b724a81e14e532972b40d863b0de3b7d1",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "321ed8d559c951e71ad2d2d69a4cf0445644e865",
        "lessThan": "2a368ccddfc492a0aa951e2caef2985f20e96503",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "4865c768b563deff1b6a6384e74a62f143427b42",
        "lessThan": "bb81702370fad22c06ca12b6e1648754dbc37e0f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "16fce6b6c0b247258c6c217fce5a48abf50f6964",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "5.15.203",
        "lessThan": "5.16",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "fs/ext4/mballoc.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "6.1.167",
        "lessThan": "6.1.168",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.6.130",
        "lessThan": "6.6.134",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.12.77",
        "lessThan": "6.12.80",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.18.14",
        "lessThan": "6.18.21",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.19.4",
        "lessThan": "6.19.11",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "fs/ext4/mballoc.c"
    ],
    "defaultStatus": "unaffected"
  }
]
Related CVEs
CVE-2026-43067

Source reference: /cveMetadata/cveId

Publisher severity

critical

Source reference: /containers/cna/metrics

Event
#40017 · Revision 1
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Publisher date
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