CVE-2024-35993: mm: turn folio_test_hugetlb into a PageType

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-20 · updated 2026-08-04

Description

In the Linux kernel, the following vulnerability has been resolved: mm: turn folio_test_hugetlb into a PageType The current folio_test_hugetlb() can be fooled by a concurrent folio split into returning true for a folio which has never belonged to hugetlbfs. This can't happen if the caller holds a refcount on it, but we have a few places (memory-failure, compaction, procfs) which do not and should not take a speculative reference. Since hugetlb pages do not use individual page mapcounts (they are always fully mapped and use the entire_mapcount field to record the number of mappings), the PageType field is available now that page_mapcount() ignores the value in this field. In compaction and with CONFIG_DEBUG_VM enabled, the current implementation can result in an oops, as reported by Luis. This happens since 9c5ccf2db04b ("mm: remove HUGETLB_PAGE_DTOR") effectively added some VM_BUG_ON() checks in the PageHuge() testing path. [willy@infradead.org: update vmcoreinfo]

Affected products

Linux kernel: from 6.6 before 6.6.30; from 6.7 before 6.8.9; 6.9-rc1, 6.9-rc2, 6.9-rc3, 6.9-rc4, 6.9-rc5 — fixed in 6.6.30, 6.8.9

How to fix

Upgrade to a fixed version: Linux kernel 6.6.30, 6.8.9. Check the vendor advisory for mitigations.

References

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