[CVE-2026-46022][MODERATE REGULAR] misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-46022
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()
Commit: fc7e9a74e32299d7e93e178ca482a0b59ef1595b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fc7e9a74e32299d7e93e178ca482a0b59ef1595b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46022
Analysis date: Wed, 27 May 2026 16:26:49 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-46022 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46022

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-46022	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'ibmasm_handle_mouse_interrupt() trusts queue reader and writer indices read from service processor MMIO registers. A compromised service processor can place an out of range index before or during interrupt handling, making the driver compute an MMIO address outside the remote input queue and read unintended device registers or outside the PCI BAR. For the CVSS the PR:N is used because no Linux user privileges are required once the service processor can influence the device registers. The issue is firmware mediated rather than directly network reachable, although some deployments may expose the service processor through a management plane. Impact is denial of service through machine check or kernel failure, with no supported information disclosure or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)  SKIP CVE-2026-46022  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE OOB HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

2. Signal breakdown
* Firmware-mediated external influence: +1. The trigger requires a compromised or malfunctioning service processor writing out-of-range MMIO queue indices.
* Weak/indirect corruption candidate: +1. This is an OOB MMIO read from a device BAR/register space, not kernel heap corruption or an attacker-controlled write.
* Reliable kernel crash / strong DoS: +1. Large indices can read outside the PCI BAR mapping and trigger a machine check exception.
* Availability impact realistic: +1. The realistic impact is machine-check or kernel failure.
* Rare hardware/configuration exposure: -1. The ibmasm driver and IBM service processor environment are specialized.
* Physical/firmware-dependent condition: -1. Exploitation depends on service processor compromise or equivalent hardware control.
* No C/I impact. The read is from unintended MMIO space and is not shown to disclose data to userspace or corrupt memory.

3. Reachability analysis
A normal local user cannot directly trigger this path unless they can compromise or control the service processor or the platform management path that feeds those MMIO registers. It is not directly network reachable against the Linux kernel, though some systems expose service processor management over a separate management network. Containers and namespaces do not lower the requirement because the vulnerable input comes from hardware/firmware state. The path is hardware-specific and uncommon.

4. Severity interpretation
This behaves like a firmware-mediated, hardware-specific DoS issue rather than an Important kernel vulnerability. The theoretical issue is OOB MMIO access, but the realistic demonstrated outcome is machine check or kernel crash. There is no supported arbitrary write, host memory corruption, information disclosure to an attacker, or privilege escalation.

5. One-sentence report phrase
A compromised IBM service processor can provide out-of-range ibmasm remote queue indices, causing an OOB MMIO read and possible machine-check DoS in `ibmasm_handle_mouse_interrupt()`.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED. The issue is firmware-mediated and hardware-specific, but it can cause machine-check DoS and may matter in environments where the service processor is reachable through a management plane.

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UPSTREAM PATCH SUMMARY
======================================================================

Patch: misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()
Commit: fc7e9a74e32299d7e93e178ca482a0b59ef1595b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fc7e9a74e32299d7e93e178ca482a0b59ef1595b

Commit description:

ibmasm_handle_mouse_interrupt() performs an out-of-bounds MMIO read
when the queue reader or writer index from hardware exceeds
REMOTE_QUEUE_SIZE (60).

A compromised service processor can trigger this by writing an
out-of-range value to the reader or writer MMIO register before
asserting an interrupt. Since writer is re-read from hardware on
every loop iteration, it can also be set to an out-of-range value
after the loop has already started.

The root cause is that get_queue_reader() and get_queue_writer() return
raw readl() values that are passed directly into get_queue_entry(),
which computes:

  queue_begin + reader * sizeof(struct remote_input)

with no bounds check. This unchecked MMIO address is then passed to
memcpy_fromio(), reading 8 bytes from unintended device registers.
For sufficiently large values the address falls outside the PCI BAR
mapping entirely, triggering a machine check exception.

Fix by checking both indices against REMOTE_QUEUE_SIZE at the top of
the loop body, before any call to get_queue_entry(). On an out-of-range
value, reset the reader register to 0 via set_queue_reader() before
breaking, so that normal queue operation can resume if the corrupted
hardware state is transient.

Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Fixes: 278d72a ("[PATCH] ibmasm driver: redesign handling of remote control events")
Cc: stable@vger.kernel.org
Cc: ychen@northwestern.edu
Signed-off-by: Tyllis Xu <LivelyCarpet87@gmail.com>
Link: https://patch.msgid.link/20260308062108.258940-1-LivelyCarpet87@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/misc/ibmasm/remote.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=fc7e9a74e32299d7e93e178ca482a0b59ef1595b

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-46022 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46022

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:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).