mm/mglru: fix and remove redundant unevictable folio handling
Summary
| CVE | CVE-2026-89757 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-11 20:20:06 UTC |
| Updated | 2026-09-11 20:20:06 UTC |
| Description | 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. |
Risk And Classification
EPSS: 0.001840000 probability, percentile 0.081400000 (date 2026-09-12)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected ac35a490237446b71e3b4b782b1596967edd0aa8 54a58d6656dd403b686b247f0bad8507cbfb45df git | Not specified |
| CNA | Linux | Linux | affected ac35a490237446b71e3b4b782b1596967edd0aa8 15d3a2a71c8bf7333d019d249ee33669e69e4275 git | Not specified |
| CNA | Linux | Linux | affected ac35a490237446b71e3b4b782b1596967edd0aa8 f7e698e326b239a91ea15844817551921209e826 git | Not specified |
| CNA | Linux | Linux | affected 6.1 | Not specified |
| CNA | Linux | Linux | unaffected 6.1 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.51 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2.4 7.2.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.3-rc1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/f7e698e326b239a91ea15844817551921209e826 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/15d3a2a71c8bf7333d019d249ee33669e69e4275 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/54a58d6656dd403b686b247f0bad8507cbfb45df | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.