CVE-2026-43158 (GCVE-0-2026-43158)
Vulnerability from cvelistv5 – Published: 2026-05-06 11:27 – Updated: 2026-05-08 12:40
VLAI?
Title
xfs: fix freemap adjustments when adding xattrs to leaf blocks
Summary
In the Linux kernel, the following vulnerability has been resolved:
xfs: fix freemap adjustments when adding xattrs to leaf blocks
xfs/592 and xfs/794 both trip this assertion in the leaf block freemap
adjustment code after ~20 minutes of running on my test VMs:
ASSERT(ichdr->firstused >= ichdr->count * sizeof(xfs_attr_leaf_entry_t)
+ xfs_attr3_leaf_hdr_size(leaf));
Upon enabling quite a lot more debugging code, I narrowed this down to
fsstress trying to set a local extended attribute with namelen=3 and
valuelen=71. This results in an entry size of 80 bytes.
At the start of xfs_attr3_leaf_add_work, the freemap looks like this:
i 0 base 448 size 0 rhs 448 count 46
i 1 base 388 size 132 rhs 448 count 46
i 2 base 2120 size 4 rhs 448 count 46
firstused = 520
where "rhs" is the first byte past the end of the leaf entry array.
This is inconsistent -- the entries array ends at byte 448, but
freemap[1] says there's free space starting at byte 388!
By the end of the function, the freemap is in worse shape:
i 0 base 456 size 0 rhs 456 count 47
i 1 base 388 size 52 rhs 456 count 47
i 2 base 2120 size 4 rhs 456 count 47
firstused = 440
Important note: 388 is not aligned with the entries array element size
of 8 bytes.
Based on the incorrect freemap, the name area starts at byte 440, which
is below the end of the entries array! That's why the assertion
triggers and the filesystem shuts down.
How did we end up here? First, recall from the previous patch that the
freemap array in an xattr leaf block is not intended to be a
comprehensive map of all free space in the leaf block. In other words,
it's perfectly legal to have a leaf block with:
* 376 bytes in use by the entries array
* freemap[0] has [base = 376, size = 8]
* freemap[1] has [base = 388, size = 1500]
* the space between 376 and 388 is free, but the freemap stopped
tracking that some time ago
If we add one xattr, the entries array grows to 384 bytes, and
freemap[0] becomes [base = 384, size = 0]. So far, so good. But if we
add a second xattr, the entries array grows to 392 bytes, and freemap[0]
gets pushed up to [base = 392, size = 0]. This is bad, because
freemap[1] hasn't been updated, and now the entries array and the free
space claim the same space.
The fix here is to adjust all freemap entries so that none of them
collide with the entries array. Note that this fix relies on commit
2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow") and
the previous patch that resets zero length freemap entries to have
base = 0.
Severity ?
8.8 (High)
Assigner
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux |
Affected:
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d08976725355b9d54d8332fce223fa281cc304a5
(git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 6a8737afbccc340e718e0b22577312826390be8b (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < a396b3d73d51355e50acdb403ba9c4cae4c1174e (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 38613c01f69e1e77e6b8acab1e8ac665d01c2f15 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < ef42a8766ff3fdf51cf72fb36d0859c09d134478 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 43f3b18679615a93bd848afde3602ba160637a46 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 24ce71852f2cee6581e2cbebc15489ed52bf63b7 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 3eefc0c2b78444b64feeb3783c017d6adc3cd3ce (git) |
|||||||
|
|||||||||
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfs: fix freemap adjustments when adding xattrs to leaf blocks\n\nxfs/592 and xfs/794 both trip this assertion in the leaf block freemap\nadjustment code after ~20 minutes of running on my test VMs:\n\n ASSERT(ichdr-\u003efirstused \u003e= ichdr-\u003ecount * sizeof(xfs_attr_leaf_entry_t)\n\t\t\t\t\t+ xfs_attr3_leaf_hdr_size(leaf));\n\nUpon enabling quite a lot more debugging code, I narrowed this down to\nfsstress trying to set a local extended attribute with namelen=3 and\nvaluelen=71. This results in an entry size of 80 bytes.\n\nAt the start of xfs_attr3_leaf_add_work, the freemap looks like this:\n\ni 0 base 448 size 0 rhs 448 count 46\ni 1 base 388 size 132 rhs 448 count 46\ni 2 base 2120 size 4 rhs 448 count 46\nfirstused = 520\n\nwhere \"rhs\" is the first byte past the end of the leaf entry array.\nThis is inconsistent -- the entries array ends at byte 448, but\nfreemap[1] says there\u0027s free space starting at byte 388!\n\nBy the end of the function, the freemap is in worse shape:\n\ni 0 base 456 size 0 rhs 456 count 47\ni 1 base 388 size 52 rhs 456 count 47\ni 2 base 2120 size 4 rhs 456 count 47\nfirstused = 440\n\nImportant note: 388 is not aligned with the entries array element size\nof 8 bytes.\n\nBased on the incorrect freemap, the name area starts at byte 440, which\nis below the end of the entries array! That\u0027s why the assertion\ntriggers and the filesystem shuts down.\n\nHow did we end up here? First, recall from the previous patch that the\nfreemap array in an xattr leaf block is not intended to be a\ncomprehensive map of all free space in the leaf block. In other words,\nit\u0027s perfectly legal to have a leaf block with:\n\n * 376 bytes in use by the entries array\n * freemap[0] has [base = 376, size = 8]\n * freemap[1] has [base = 388, size = 1500]\n * the space between 376 and 388 is free, but the freemap stopped\n tracking that some time ago\n\nIf we add one xattr, the entries array grows to 384 bytes, and\nfreemap[0] becomes [base = 384, size = 0]. So far, so good. But if we\nadd a second xattr, the entries array grows to 392 bytes, and freemap[0]\ngets pushed up to [base = 392, size = 0]. This is bad, because\nfreemap[1] hasn\u0027t been updated, and now the entries array and the free\nspace claim the same space.\n\nThe fix here is to adjust all freemap entries so that none of them\ncollide with the entries array. Note that this fix relies on commit\n2a2b5932db6758 (\"xfs: fix attr leaf header freemap.size underflow\") and\nthe previous patch that resets zero length freemap entries to have\nbase = 0."
}
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"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
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}
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"dateReserved": "2026-05-01T14:12:55.990Z",
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"date": "2026-05-09",
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"percentile": "0.16466"
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}
}
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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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