Google: sys-kernel/cchost-kernel-6_18, sys-kernel/csql-kernel-6_18, sys-kernel/lakitu-kernel-6_18, sys-kernel/lakitu-nc-kernel-6_18: security update to 19999.44.106

medium Tenable Cloud Security Plugin ID 475610

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

- In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: Acquire init_mm read lock
on attribute changes to avoid UAF A previous commit protected against races between ptdump and CPA
collapse, however one still exists between attribute changes and collapse as reported by Denis V. Lunev
(linked). When an attribute change arises, a lockless page table walker obtains a PTE entry, which is
later written to via set_pte_atomic(): ... -> change_page_attr_set_clr() -> __change_page_attr_set_clr()
-> __change_page_attr() -> _lookup_address_cpa() -> lookup_address_in_pgd_attr() -> [ lockless page table
walker ] -> set_pte_atomic() There is nothing preventing a concurrent CPA collapse which can free the PTE
that was retrieved here, resulting in a use-after-free. With the mmap write lock taken on init_mm over CPA
collapse, resolve this race by acquiring an mmap read lock on init_mm over __change_page_attr_set_clr().
This locks across the whole operation over which the walk and the PTE entry write occurs, solving the
race. It is safe to do this here, as no spinlocks are held upon entry to __change_page_attr_set_clr().
However, the lock must not be held over an allocation, as allocation can trigger reclaim and shrinkers may
call into CPA recursively, making deadlocks possible (init_mm -> ... -> fs_reclaim -> init_mm). A page
table is allocated when a huge page needs to be split: -> change_page_attr_set_clr() ->
__change_page_attr_set_clr() -> __change_page_attr() -> split_large_page() [ pagetable_alloc() ] ->
__split_large_page() Avoid deadlocks by dropping the mmap lock across pagetable_alloc() in
split_large_page() and track whether this is needed by adding a new 'init_mm_read_locked' flag to struct
cpa_data. This is safe as __split_large_page() (called with locks re-established) revalidates that the
page table entry is the same as it was prior to the locks being dropped and __change_page_attr() repeats
the entire page table walk whenever a split occurs, so concurrent split and collapse are accounted for.
Concurrent ptdump is also safe as the lock is only dropped over page table allocation during which time
the page table has not yet been modified. The CPA_COLLAPSE flag is only set by set_memory_rox(), which
exclusively operates upon vmalloc ranges, and on x86 only within the module mapping space. This is
important, because some callers directly invoke __change_page_attr_set_clr(), bypassing this lock.
However, none of these operate within the module mapping space. * cpa_process_alias() - a recursive helper
called by __change_page_attr_set_clr(). * __set_memory_enc_pgtable() - operates on the direct mapping and
(via __vmbus_establish_gpadl()) the vmalloc mapping space. * __set_pages_[n]p() - called by
set_direct_map_[invalid, default, valid]_noflush(), __kernel_map_pages() - operates on the direct map. *
kernel_[un]map_pages_in_pgd() - operates on EFI ranges. This work is based upon Denis V. Lunev's excellent
analysis of the bug with gratitude. [ dhansen: move to imperative voice in changelog ] (CVE-2026-97533)

Solution

Update the sys-kernel/cchost-kernel-6_18 library and its related packages to version 19999.44.106 or later.

Plugin Details

Severity: Medium

ID: 475610

Version: Revision 1.1

Type: Local

Family: Google COS Security Checks

Published: 10/16/2026

Updated: 10/16/2026

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 93.23

Vendor

Vendor Severity: LOW

CVSS v2

Risk Factor: High

Base Score: 7.2

Temporal Score: 5.3

Vector: CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS Score Source: CVE-2026-97533

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 9/25/2026

Reference Information

CVE: CVE-2026-97533

Detections

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