* [CVE-2026-97942][MODERATE REGULAR] x86/alternatives: Exclude text poking against change_page_attr()
@ 2026-09-26 18:15 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-26 18:15 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97942
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: x86/alternatives: Exclude text poking against change_page_attr()
Commit: 281e6f536f2f3f95d91938c5bd7ba9bcb4c1049d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=281e6f536f2f3f95d91938c5bd7ba9bcb4c1049d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97942
Analysis date: Sat, 26 Sep 2026 14:15:48 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97942 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97942
The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.
The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.
Published priority for this report: MODERATE REGULAR
Manual review required: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-97942 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97942 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;CWE-667;**CWE-476;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race between x86 text poking and change_page_attr can occur while vmalloc_to_page resolves pages from a shared execmem ROX range. Concurrent page table collapse or PMD hugepage changes can make page resolution fail, causing the BUG_ON in __text_poke and a kernel Oops or panic. The confirmed impact is a local denial of service and reliable triggering requires a timing window during module loading or another static call update. For the CVSS the PR:L value in the paranoid score reflects environments where a local user can indirectly stimulate module autoload or a privileged udev action, although direct module loading normally requires administrative privileges. The issue is not network reachable. A higher impact remains plausible because the resolved page is later used by text poking to write executable kernel code, and an incorrect or stale page result could potentially redirect that write to unintended kernel memory. This memory corruption outcome is not demonstrated and requires manual source level validation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-97942 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE READ LOCK DANGER INIT RACE HARDWARE MEMORY DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
Conservative signals:
* +1 Reliable kernel crash. The race can make `vmalloc_to_page()` return NULL, reaching the explicit `BUG_ON()` in `__text_poke()` and producing an observed kernel Oops.
* +1 Weak or indirect corruption candidate. Page resolution occurs while CPA changes the relevant page-table structure, but the only established bad result is failed translation rather than a useful stale-page or wrong-page primitive.
* +1 Broadly exercised path. x86 module loading, static-call transformation, and executable module-memory permission changes are normal kernel operations on affected configurations.
* -1 Hard timing. The report describes an intermittent race between text poking and concurrent CPA or `set_memory_*()` activity, without evidence that one below-admin attacker controls both sides.
Raw conservative arithmetic: `1 + 1 + 1 - 1 = 2`.
Paranoid signals:
* The same three positive signals apply.
* No timing penalty is applied because the competing operations can recur across module activity, so the race is not inherently one-shot. Attacker-controlled repetition is still not established.
Raw paranoid arithmetic: `1 + 1 + 1 = 3`.
Not awarded:
* No UAF or stale post-lifetime object use is established.
* No controlled reclaim, arbitrary write, wrong-page write, information disclosure, or privilege escalation is demonstrated.
* The fact that the resulting page is later used by text poking does not prove that `vmalloc_to_page()` can return an incorrect attacker-useful page rather than NULL.
* No extra Availability point is awarded because the Oops and possible panic are the same crash consequence.
* No active-state retirement or translation-domain reinterpretation signal applies. The fix serializes a page-table lookup against CPA rather than restoring bypassed retirement of an old mapping.
* No remote or namespace-scoped trigger is established.
Repeated-release checks:
* No first lifetime-ending release exists.
* No dangling reference survives into a second release.
* No repeated refcount mutation exists.
* The dedicated repeated-release point and UAF floor are not applicable.
3. Reachability analysis
The observed path runs in a UID 0 `udev-worker` during `finit_module()`. Direct module loading requires host-level authority, but the supplied evidence does not resolve whether an ordinary local action can indirectly induce the complete vulnerable concurrency through automatic module loading and privileged udev processing. Therefore `HostAdminRequired=UNKNOWN`, and no privilege penalty is applied.
Kernel module loading is not an attacker-obtainable namespace-scoped operation, so `NamespaceScopedPrivilege=NO`. No special physical hardware is required, and the report reproduces the issue under QEMU. The affected configuration requires `CONFIG_ARCH_HAS_EXECMEM_ROX` and concurrent activity within a shared execmem vmalloc range. The race is intermittent, but potentially retriable under repeated module activity.
4. Primitive and severity interpretation
The exact established primitive is an unsynchronized `vmalloc_to_page()` lookup while CPA may collapse or split the relevant page-table hierarchy. The demonstrated result is a NULL page result followed by an intentional `BUG_ON()`, producing kernel DoS.
This is CLASS_C because no actual lifetime violation, stale object use, page-table UAF, wrong-page return, or write to an unintended page is established. The possible wrong-page text-poking scenario is a review question, not a scored primitive.
`ImportantCandidate=NO` because current evidence supports crash-only behavior without an independently useful corruption or boundary-bypass mechanism. `AutoDowngradeAllowed=YES` because no unresolved concrete Class A or Class B primitive would be discarded. Operational severity is ordinary to borderline Moderate, with manual source review appropriate due to the proximity of the race to kernel text modification.
5. One-sentence report phrase
A race between x86 text poking and CPA page-table changes can make vmalloc_to_page fail and trigger a kernel Oops during module loading, while no useful wrong-page write or privilege-escalation primitive is currently established.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm whether racing `vmalloc_to_page()` can only return NULL or can return a stale or incorrect `struct page` that is subsequently used as the writable text-poking alias.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: x86/alternatives: Exclude text poking against change_page_attr()
Commit: 281e6f536f2f3f95d91938c5bd7ba9bcb4c1049d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=281e6f536f2f3f95d91938c5bd7ba9bcb4c1049d
Commit description:
From time to time, the following BUG can be observed
in the x86 alternatives patching code [0]:
> kernel BUG at arch/x86/kernel/alternative.c:2576!
> Oops: invalid opcode: 0000 [#1] SMP NOPTI
> CPU: 0 UID: 0 PID: 355 Comm: (udev-worker) Not tainted 7.1.3-1-default #1 PREEMPT(full) openSUSE Tumbleweed 8c1795b03ec64f997e57a8ad38b1161e3b98da64
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022
> RIP: 0010:__text_poke+0x2aa/0x450
> Call Trace:
> <TASK>
> smp_text_poke_batch_finish+0x2a7/0x320
> __static_call_transform+0xb7/0x220
> arch_static_call_transform+0x5b/0xb0
> __static_call_init+0xe9/0x270
> static_call_module_notify+0x11f/0x150
> notifier_call_chain+0x61/0xe0
> blocking_notifier_call_chain_robust+0x63/0xc0
> load_module+0x1c92/0x20c0
> init_module_from_file+0xd8/0x140
> idempotent_init_module+0x100/0x2f0
> __x64_sys_finit_module+0x71/0xe0
> do_syscall_64+0xe1/0x610
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
which matches the following BUG_ON() in alternative.c:
/*
* If something went wrong, crash and burn since recovery paths are not
* implemented.
*/
BUG_ON(!pages[0] || (cross_page_boundary && !pages[1]));
This can happen if vmalloc_to_page() fails, for any reason. Such can happen
if text poking races with CPA, which can possibly result in the collapsing
of page tables (or breaking of PMD hugepages). It is not a problem for most
users of vmalloc_to_page() (they solely own the vmalloc'd range) but, when
CONFIG_ARCH_HAS_EXECMEM_ROX=y, various modules own a single execmem vmalloc
range, and can call set_memory_*() in parallel on it. This can happen to
race against __text_poke and cause havoc in vmalloc_to_page().
Fix it by excluding against CPA using the init_mm mmap read lock.
[ dhansen: Fix up SoB ordering. The actual code flow here was:
Pedro=>Lorenzo=>Mike=>Me which is reflected in the SoB chain
now. I *believe* Mike simply picked up Lorenzo's update to
Pedro's post from the Link ]
Fixes: 64f6a4e ("x86: re-enable EXECMEM_ROX support")
Reported-by: Jiri Slaby <[email protected]>
Reported-by: Steffen Dirkwinkel <[email protected]>
Signed-off-by: Pedro Falcato <[email protected]>
Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>
Co-developed-by: Lorenzo Stoakes (ARM) <[email protected]>
Signed-off-by: Mike Rapoport (Microsoft) <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Tested-by: Jiri Slaby <[email protected]>
Tested-by: Atish Patra <[email protected]>
Tested-by: Nikunj A Dadhania <[email protected]>
Cc: [email protected]
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1271202 [0]
Link: https://lore.kernel.org/linux-mm/[email protected]/
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
arch/x86/kernel/alternative.c
mm/555ea1d43a12c30a8f1eaf10c899b3790d728f33.camel
Diff excerpt:
Not included in this email. See the upstream URL for the full patch.
Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=281e6f536f2f3f95d91938c5bd7ba9bcb4c1049d
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97942 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97942
The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.
The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.
The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.
Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:
Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.
CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.
A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.
Conservative ActionableScore: 2
Paranoid ActionableScore: 3
The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.
For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:
ActionableScore below 5 -> MODERATE REGULAR
ActionableScore 5 or more -> MODERATE 7.0
The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.
There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).
KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.
AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).
Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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