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

high Tenable Self-Hosted Container Security Plugin ID 475373

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: KVM: x86/mmu: Consume the locked rmap
value in the lockless rmap walk __kvm_rmap_lock() deliberately elides the rmap lock when it observes an
empty rmap. In that case kvm_rmap_lock_readonly() also re-enables preemption and returns zero, so the
caller holds neither the rmap lock nor a preemption reference. The elision documents the invariant it
relies on: * Elide the lock if the rmap is empty, as lockless walkers (read-only * mode) don't need to
(and can't) walk an empty rmap, nor can they add * entries to the rmap. I.e. the only paths that process
empty rmaps * do so while holding mmu_lock for write, and are mutually exclusive. kvm_rmap_age_gfn_range()
ignores the returned value and unconditionally enters for_each_rmap_spte_lockless(). The iterator started
with rmap_get_first(), which re-reads rmap_head->val rather than using the value returned by the lock. If
a writer populates the rmap between the lock's read and the iterator's re-read, the aging path walks the
newly installed rmap without holding its lock. For a KVM_RMAP_MANY rmap this leaves the walker following a
pte_list_desc chain that it never locked. A writer holding mmu_lock for write may free that chain (e.g.
kvm_zap_all_rmap_sptes() on the recycle path, or any rmap zap) via kmem_cache_free() while the walk is in
progress, giving a slab use-after-free. Nothing serialises the two: the aging path runs without mmu_lock
when CONFIG_KVM_MMU_LOCKLESS_AGING=y, and the rmap lock that would otherwise exclude the writer was
elided. Because the empty path re-enables preemption, the interval between the two reads can span an
arbitrary scheduling delay. Fix the class of bug by having the lockless walk consume the value returned by
the lock instead of re-reading the rmap. Split rmap_get_first() into __rmap_get_first(), which starts an
iterator from an already-read rmap value, and make for_each_rmap_spte_lockless() take that value and call
__rmap_get_first() directly. kvm_rmap_age_gfn_range() passes the value returned by
kvm_rmap_lock_readonly(): when the lock was elided the value is zero, __rmap_get_first() returns NULL, and
the walk is skipped. No lockless walker re-reads the rmap, so the lock-elision invariant cannot be
violated, and no lock()-without-paired-unlock() path is added to the aging code. (CVE-2026-89928)

Solution

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

Plugin Details

Severity: High

ID: 475373

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: 92.82

Vendor

Vendor Severity: HIGH

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

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

CVSS Score Source: CVE-2026-89928

CVSS v3

Risk Factor: High

Base Score: 8.8

Temporal Score: 7.7

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/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: 9/16/2026

Reference Information

CVE: CVE-2026-89928

Detections

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