CVE-2026-43067 (GCVE-0-2026-43067)
Vulnerability from cvelistv5 – Published: 2026-05-05 15:23 – Updated: 2026-05-08 12:40
VLAI?
Title
ext4: handle wraparound when searching for blocks for indirect mapped blocks
Summary
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().
Severity ?
9.8 (Critical)
Assigner
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Affected:
9d89b9d55e25cb340c5b4b769876edc551b7a9ff , < f89bba144938921a2249237ad04a0183ff3f8930
(git)
Affected: 1b0edd6022a3f44ce87fea9959a9310f4628fbea , < 83170a05908b6cf2fb3235d3065bf613ff866f3c (git) Affected: 9eea2f57d11b30049ff996ac3eff6e0dc8089e5f , < 4bec4a498ce86314d470ae6144120461f2138c29 (git) Affected: 34c803edc0b3365a42efcf9815acab63b4cf54e0 , < 12624c5b724a81e14e532972b40d863b0de3b7d1 (git) Affected: 321ed8d559c951e71ad2d2d69a4cf0445644e865 , < 2a368ccddfc492a0aa951e2caef2985f20e96503 (git) Affected: 4865c768b563deff1b6a6384e74a62f143427b42 , < bb81702370fad22c06ca12b6e1648754dbc37e0f (git) Affected: 16fce6b6c0b247258c6c217fce5a48abf50f6964 (git) |
||
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{
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"value": "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-\u003eac_g_ex.fe_group is \u003e= ngroups (for instance, if the goal\n group was populated via stream allocation from s_mb_last_groups),\n then start will be \u003e= 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()."
}
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{
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"dateReserved": "2026-05-01T14:12:55.981Z",
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"date": "2026-05-08",
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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