CVE-2026-89757 (GCVE-0-2026-89757)
Vulnerability from cvelistv5
Published
2026-09-11 19:46
Modified
2026-10-30 12:32
Severity ?
VLAI Severity ?
EPSS score ?
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 | ||
|---|---|---|---|---|
| Linux | Linux |
Version: ac35a490237446b71e3b4b782b1596967edd0aa8 Version: ac35a490237446b71e3b4b782b1596967edd0aa8 Version: ac35a490237446b71e3b4b782b1596967edd0aa8 Version: ac35a490237446b71e3b4b782b1596967edd0aa8 Version: ac35a490237446b71e3b4b782b1596967edd0aa8 Version: ac35a490237446b71e3b4b782b1596967edd0aa8 |
||
{
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"versions": [
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"status": "unaffected",
"version": "6.18.51",
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{
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"status": "unaffected",
"version": "7.2.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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"nodes": [
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"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."
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:32:56.012Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/e9f2160081a1e3ebb285bd71be3382abaeb8390a"
},
{
"url": "https://git.kernel.org/stable/c/b1d7c69e6c7d3ec47513b911ce7529e56d183dad"
},
{
"url": "https://git.kernel.org/stable/c/49193dac48d30eee2a21da88a7262d52a7feefae"
},
{
"url": "https://git.kernel.org/stable/c/54a58d6656dd403b686b247f0bad8507cbfb45df"
},
{
"url": "https://git.kernel.org/stable/c/15d3a2a71c8bf7333d019d249ee33669e69e4275"
},
{
"url": "https://git.kernel.org/stable/c/f7e698e326b239a91ea15844817551921209e826"
}
],
"title": "mm/mglru: fix and remove redundant unevictable folio handling",
"x_generator": {
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}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-89757",
"datePublished": "2026-09-11T19:46:59.830Z",
"dateReserved": "2026-09-11T19:38:34.763Z",
"dateUpdated": "2026-10-30T12:32:56.012Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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