Google: sys-kernel/csql-kernel-6_1, sys-kernel/lakitu-kernel-6_1: security update to 18244.521.23

medium Tenable Cloud Security Plugin ID 451071

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: mm/ksm: fix flag-dropping behavior in
ksm_madvise syzkaller discovered the following crash: (kernel BUG) [ 44.607039] ------------[ cut here
]------------ [ 44.607422] kernel BUG at mm/userfaultfd.c:2067! [ 44.608148] Oops: invalid opcode: 0000
[#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 44.608814] CPU: 1 UID: 0 PID: 2475 Comm: reproducer Not tainted
6.16.0-rc6 #1 PREEMPT(none) [ 44.609635] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 44.610695] RIP:
0010:userfaultfd_release_all+0x3a8/0x460 <snip other registers, drop unreliable trace> [ 44.617726] Call
Trace: [ 44.617926] <TASK> [ 44.619284] userfaultfd_release+0xef/0x1b0 [ 44.620976] __fput+0x3f9/0xb60 [
44.621240] fput_close_sync+0x110/0x210 [ 44.622222] __x64_sys_close+0x8f/0x120 [ 44.622530]
do_syscall_64+0x5b/0x2f0 [ 44.622840] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 44.623244] RIP:
0033:0x7f365bb3f227 Kernel panics because it detects UFFD inconsistency during userfaultfd_release_all().
Specifically, a VMA which has a valid pointer to vma->vm_userfaultfd_ctx, but no UFFD flags in
vma->vm_flags. The inconsistency is caused in ksm_madvise(): when user calls madvise() with
MADV_UNMEARGEABLE on a VMA that is registered for UFFD in MINOR mode, it accidentally clears all flags
stored in the upper 32 bits of vma->vm_flags. Assuming x86_64 kernel build, unsigned long is 64-bit and
unsigned int and int are 32-bit wide. This setup causes the following mishap during the &= ~VM_MERGEABLE
assignment. VM_MERGEABLE is a 32-bit constant of type unsigned int, 0x8000'0000. After ~ is applied, it
becomes 0x7fff'ffff unsigned int, which is then promoted to unsigned long before the & operation. This
promotion fills upper 32 bits with leading 0s, as we're doing unsigned conversion (and even for a signed
conversion, this wouldn't help as the leading bit is 0). & operation thus ends up AND-ing vm_flags with
0x0000'0000'7fff'ffff instead of intended 0xffff'ffff'7fff'ffff and hence accidentally clears the upper
32-bits of its value. Fix it by changing `VM_MERGEABLE` constant to unsigned long, using the BIT() macro.
Note: other VM_* flags are not affected: This only happens to the VM_MERGEABLE flag, as the other VM_*
flags are all constants of type int and after ~ operation, they end up with leading 1 and are thus
converted to unsigned long with leading 1s. Note 2: After commit 31defc3b01d9 ("userfaultfd: remove
(VM_)BUG_ON()s"), this is no longer a kernel BUG, but a WARNING at the same place: [ 45.595973] WARNING:
CPU: 1 PID: 2474 at mm/userfaultfd.c:2067 but the root-cause (flag-drop) remains the same. [akpm@linux-
foundation.org: rust bindgen wasn't able to handle BIT(), from Miguel] (CVE-2025-40040)

Solution

Update the sys-kernel/csql-kernel-6_1 library and its related packages to version 18244.521.23 or later.

Plugin Details

Severity: Medium

ID: 451071

Version: Revision 1.1

Type: Local

Family: Google COS Security Checks

Published: 10/1/2026

Updated: 10/1/2026

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.36

Vendor

Vendor Severity: LOW

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Temporal Score: 3.4

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

CVSS Score Source: CVE-2025-40040

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: 10/28/2025

Reference Information

CVE: CVE-2025-40040

Detections

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