* [CVE-2026-97947][LOW] x86/amd_node: Fix potential NULL pointer dereference
@ 2026-09-29 22:08 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-29 22:08 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97947
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: x86/amd_node: Fix potential NULL pointer dereference
Commit: fcd19bc829eca237742a3b123f839ad1c473ec85
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fcd19bc829eca237742a3b123f839ad1c473ec85
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97947
Analysis date: Tue, 29 Sep 2026 18:08:29 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97947 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97947
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-97947 LOW https://www.kernelcve.org/list/?q=CVE-2026-97947 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:N/I:N/A:H';**CWE-476;CWE-665;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A failed amd_smn_init can leave amd_roots as NULL while the exported amd_smn_read and amd_smn_write interfaces remain available to other kernel components. A later SMN access can reach __amd_smn_rw and dereference amd_roots before a valid root device array exists, potentially causing a kernel Oops or crash. For the CVSS the PR:L value is used for the paranoid score because a reduced capability service or local process may be able to trigger a driver path that performs the SMN access, although reliable triggering still depends on a prior initialization failure and suitable AMD hardware. The issue is not directly network reachable. Impact is limited to local denial of service because the available code shows a NULL pointer dereference without a UAF, OOB access, information leak, or write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE WRITE OOB NULLPTR INIT HARDWARE DEBUGFS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Reliable kernel crash / strong DoS. If `amd_smn_init()` fails before allocating `amd_roots`, a later exported SMN access can index through a NULL base pointer and cause a kernel Oops or crash.
* +0 Weak corruption concern. The established primitive is an invalid NULL-based access, not a UAF, overwrite, disclosure, or reusable stale object.
* No privilege penalty was applied because host-admin-equivalent privilege is not positively established for the complete trigger.
* No hardware penalty was applied. AMD hardware is required, but the evidence does not establish rare or physical-only hardware.
* No race penalty was applied because this is an initialization-state logic error, not a timing race.
* Remote reachability is not established.
* Ordinary local unprivileged reachability is not established.
* Controlled reclaim, arbitrary write, information disclosure, and attacker-controlled target selection are not demonstrated.
* No C or I signal is awarded. The patch establishes only an invalid access and availability impact.
* No extra Availability point is awarded because it would duplicate the same Oops or crash consequence.
* No repeated release or refcount mutation exists. The dedicated signal and UAF floors do not apply.
3. Reachability analysis
Triggering requires two stages. First, `amd_smn_init()` must fail before `amd_roots` is allocated, such as after failure of the PCI configuration-region exclusivity setup. Second, another kernel component must call exported `amd_smn_read()` or `amd_smn_write()`.
The supplied code does not expose these functions directly to ordinary userspace, and the debugfs interface shown in context appears to be created only after successful initialization. No network path is present. The complete privilege boundary of possible downstream callers is not supplied, so `HostAdminRequired` remains `UNKNOWN` rather than being inferred as either host admin or below host admin.
AMD SMN and PCI root-device state are global hardware resources, but the supplied evidence does not fully resolve every possible caller or delegated interface. Therefore namespace-scoped completion is not established. No race is required, and no prior attacker-controlled setup is positively demonstrated.
4. Primitive and severity interpretation
The exact primitive is a NULL-based array access in `__amd_smn_rw()` when `amd_roots` was never allocated. For node zero this is a direct NULL dereference. For a nonzero node it remains an access derived from a NULL base and is expected to fault on a low invalid address.
This is neither active structured stale storage nor fixed stale storage because no object has been freed. There is no UAF, double release, refcount corruption, OOB access to an allocated object, or post-lifetime operation. The correct classification is `CLASS_C`.
The demonstrated consequence is a kernel Oops or possible crash. A stronger consequence such as privilege escalation would require an additional write, disclosure, or lifetime-corruption primitive that is not supported by the patch or supplied context. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` because the issue is a constrained invalid-state dereference without unresolved exploitation leverage.
5. One-sentence report phrase
A failed AMD SMN initialization can leave `amd_roots` NULL and allow a later in-kernel SMN access to cause a NULL pointer dereference and local denial of service, with no demonstrated UAF, information disclosure, write primitive, or remote trigger.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The established impact is limited to a NULL-pointer crash path, and no meaningful memory-corruption, authorization, ownership, or lifetime primitive remains unresolved.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: x86/amd_node: Fix potential NULL pointer dereference
Commit: fcd19bc829eca237742a3b123f839ad1c473ec85
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fcd19bc829eca237742a3b123f839ad1c473ec85
Commit description:
amd_smn_read/write() are exported functions around __amd_smn_rw(), so
they are always available even if amd_smn_init() fails. In that case,
'amd_roots' is NULL and __amd_smn_rw() will access uninitialized memory.
Then, commit:
8351845 ("x86/amd_node: Add SMN offsets to exclusive region access")
added the 'smn_exclusive' flag, which indicated the calls to
pci_request_config_region_exclusive() succeeded, to prevent
concurrent userspace access.
Commit:
0a4b61d ("x86/amd_node: Fix AMD root device caching")
re-ordered initialization so pci_request_config_region_exclusive() is
called earlier and a failure exits amd_smn_init() before allocating
'amd_roots'. The setting of 'smn_exclusive' moved to the end of
amd_smn_init(), after 'amd_roots' is allocated. It became redundant
and can be removed.
Replace 'smn_exclusive' with directly checking 'amd_roots', to fix a
potential NULL pointer dereference and to simplify the logic.
[ bp: Reorg commit message, touchup comment. ]
[ mingo: Rebase & further touchups. ]
Fixes: 77466b7 ("x86/amd_node: Remove dependency on AMD_NB")
Signed-off-by: Jason Andryuk <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: Yazen Ghannam <[email protected]>
Reviewed-by: Mario Limonciello (AMD) <[email protected]>
Cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
arch/x86/kernel/amd_node.c
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=fcd19bc829eca237742a3b123f839ad1c473ec85
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97947 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97947
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:N/I:N/A:H
The Best / paranoid CVSS score: 4.7
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: unknown
Paranoid ActionableScore: 1
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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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