FKIE_CVE-2026-89757
Vulnerability from fkie_nvd - Published: 2026-09-11 20:20 - Updated: 2026-09-11 20:20
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
mm/mglru: fix and remove redundant unevictable folio handling
sort_folio() has a shortcut for moving folios that are no longer evictable
but are still sitting on a generation list. However, this shortcut is
buggy. It does not follow the PG_lru usage convention, and it has a more
serious issue.
Unevictable folios are not threaded on lists[LRU_UNEVICTABLE], so that
folio->lru can be reused to hold folio->mlock_count (see the comment in
lruvec_init()). Hence lruvec_add_folio() skips the list_add() for them,
and every other place that turns a folio unevictable initialises
mlock_count explicitly: lru_add() sets it to 0, __mlock_folio() and
__mlock_new_folio() set it to !!folio_test_mlocked(folio). sort_folio()
sets nothing, and the lru_gen_del_folio() right above it may have already
poisoned folio->lru via list_del(), so mlock_count ends up aliasing
LIST_POISON2, which reads as 0x122, i.e. 290. The result is user
visible. On munlock, __munlock_folio() decrements that bogus count, finds
it still non-zero and bails out before clearing PG_mlocked, so the folio
remains unevictable and the Mlocked accounting stays inflated until the
folio is freed.
The shortcut also touches the LRU flags in the wrong order. It calls
lru_gen_del_folio() while PG_lru is still set, so a concurrent
folio_test_clear_lru() (e.g. compaction, folio_isolate_lru()) can succeed
on a folio that has already been taken off the generation list, which may
lead to unexpected behavior.
So fix it by isolating them as common folios and letting the generic
shrink path cull them. This matches the classical LRU behavior, and there
should be no visible effect on the generic eviction or isolation behavior.
There is no performance concern either, such a folio goes through this
once, and then it is off the generation lists for good.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"mm/vmscan.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "54a58d6656dd403b686b247f0bad8507cbfb45df",
"status": "affected",
"version": "ac35a490237446b71e3b4b782b1596967edd0aa8",
"versionType": "git"
},
{
"lessThan": "15d3a2a71c8bf7333d019d249ee33669e69e4275",
"status": "affected",
"version": "ac35a490237446b71e3b4b782b1596967edd0aa8",
"versionType": "git"
},
{
"lessThan": "f7e698e326b239a91ea15844817551921209e826",
"status": "affected",
"version": "ac35a490237446b71e3b4b782b1596967edd0aa8",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"mm/vmscan.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.1"
},
{
"lessThan": "6.1",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/mglru: fix and remove redundant unevictable folio handling\n\nsort_folio() has a shortcut for moving folios that are no longer evictable\nbut are still sitting on a generation list. However, this shortcut is\nbuggy. It does not follow the PG_lru usage convention, and it has a more\nserious issue.\n\nUnevictable folios are not threaded on lists[LRU_UNEVICTABLE], so that\nfolio-\u003elru can be reused to hold folio-\u003emlock_count (see the comment in\nlruvec_init()). Hence lruvec_add_folio() skips the list_add() for them,\nand every other place that turns a folio unevictable initialises\nmlock_count explicitly: lru_add() sets it to 0, __mlock_folio() and\n__mlock_new_folio() set it to !!folio_test_mlocked(folio). sort_folio()\nsets nothing, and the lru_gen_del_folio() right above it may have already\npoisoned folio-\u003elru via list_del(), so mlock_count ends up aliasing\nLIST_POISON2, which reads as 0x122, i.e. 290. The result is user\nvisible. On munlock, __munlock_folio() decrements that bogus count, finds\nit still non-zero and bails out before clearing PG_mlocked, so the folio\nremains unevictable and the Mlocked accounting stays inflated until the\nfolio is freed.\n\nThe shortcut also touches the LRU flags in the wrong order. It calls\nlru_gen_del_folio() while PG_lru is still set, so a concurrent\nfolio_test_clear_lru() (e.g. compaction, folio_isolate_lru()) can succeed\non a folio that has already been taken off the generation list, which may\nlead to unexpected behavior.\n\nSo fix it by isolating them as common folios and letting the generic\nshrink path cull them. This matches the classical LRU behavior, and there\nshould be no visible effect on the generic eviction or isolation behavior.\n\nThere is no performance concern either, such a folio goes through this\nonce, and then it is off the generation lists for good."
}
],
"id": "CVE-2026-89757",
"lastModified": "2026-09-11T20:20:06.767",
"metrics": {},
"published": "2026-09-11T20:20:06.767",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/15d3a2a71c8bf7333d019d249ee33669e69e4275"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/54a58d6656dd403b686b247f0bad8507cbfb45df"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/f7e698e326b239a91ea15844817551921209e826"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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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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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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