ext4: handle wraparound when searching for blocks for indirect mapped blocks_CVE-2026-43067

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: handle wraparound when searching for blocks for indirect mapped blocks\n\nCommit 4865c768b563 (\"ext4: always allocate blocks only from groups\ninode can use\") restricts what blocks will be allocated for indirect\nblock based files to block numbers that fit within 32-bit block\nnumbers.\n\nHowever, when using a review bot running on the latest Gemini LLM to\ncheck this commit when backporting into an LTS based kernel, it raised\nthis concern:\n\n   If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal\n   group was populated via stream allocation from s_mb_last_groups),\n   then start will be >= ngroups.\n\n   Does this allow allocating blocks beyond the 32-bit limit for\n   indirect block mapped files? The commit message mentions that\n   ext4_mb_scan_groups_linear() takes care to not select unsupported\n   groups. However, its loop uses group = *start, and the very first\n   iteration will call ext4_mb_scan_group() with this unsupported\n   group because next_linear_group() is only called at the end of the\n   iteration.\n\nAfter reviewing the code paths involved and considering the LLM\nreview, I determined that this can happen when there is a file system\nwhere some files/directories are extent-mapped and others are\nindirect-block mapped.  To address this, add a safety clamp in\next4_mb_scan_groups().",
    "published": "2026-05-05T15:23:26.717Z",
    "modified": "2026-05-08T12:40:18.665Z",
    "type": "cve",
    "title": "ext4: handle wraparound when searching for blocks for indirect mapped blocks",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/f89bba144938921a2249237ad04a0183ff3f8930\nhttps://git.kernel.org/stable/c/83170a05908b6cf2fb3235d3065bf613ff866f3c\nhttps://git.kernel.org/stable/c/4bec4a498ce86314d470ae6144120461f2138c29\nhttps://git.kernel.org/stable/c/12624c5b724a81e14e532972b40d863b0de3b7d1\nhttps://git.kernel.org/stable/c/2a368ccddfc492a0aa951e2caef2985f20e96503\nhttps://git.kernel.org/stable/c/bb81702370fad22c06ca12b6e1648754dbc37e0f",
    "id": "CVE-2026-43067",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 9d89b9d55e25cb340c5b4b769876edc551b7a9ff\nLinux Linux 1b0edd6022a3f44ce87fea9959a9310f4628fbea\nLinux Linux 9eea2f57d11b30049ff996ac3eff6e0dc8089e5f\nLinux Linux 34c803edc0b3365a42efcf9815acab63b4cf54e0\nLinux Linux 321ed8d559c951e71ad2d2d69a4cf0445644e865\nLinux Linux 4865c768b563deff1b6a6384e74a62f143427b42\nLinux Linux 16fce6b6c0b247258c6c217fce5a48abf50f6964\nLinux Linux 6.1.167\nLinux Linux 6.6.130\nLinux Linux 6.12.77\nLinux Linux 6.18.14\nLinux Linux 6.19.4",
    "sourceHref": "",
    "cvss": {
        "score": 9.8,
        "severity": "CRITICAL",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
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            "privilegesRequired": "",
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "9d89b9d55e25cb340c5b4b769876edc551b7a9ff",
    "vendor": "Linux",
    "ai_description": "A vulnerability in the Linux kernel allows for the allocation of blocks beyond the 32-bit limit for indirect block mapped files, potentially leading to data corruption or other security issues.",
    "ai_severity": "Critical",
    "ai_vendor": "Linux",
    "ai_product": "Linux Kernel",
    "ai_version": "6.1.167, 6.6.130, 6.12.77, 6.18.14, 6.19.4",
    "ai_score": 9.8
}