[CVE-2026-74617][MODERATE REGULAR] dibs: initialise dibs->lock in dibs_dev_alloc()

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

CVE: CVE-2026-74617
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: dibs: initialise dibs->lock in dibs_dev_alloc()
Commit: fe79571f40434b257d68cbfb7b3ae93a794d8a11
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe79571f40434b257d68cbfb7b3ae93a794d8a11
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74617
Analysis date: Sat, 22 Aug 2026 12:30:08 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like. Manual review recommended only to confirm whether GID events can be attacker-influenced in the deployed ISM environment
Manual review required: YES

Summary:
A DIBS device may receive a GID event interrupt before `dibs->lock` is initialized, allowing the ISM interrupt handler to take an uninitialized spinlock and potentially crash or deadlock the kernel during a narrow device initialization window.

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

The original Linux kernel CVE announcement for CVE-2026-74617 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74617

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-2026-74617	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	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-665;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A DIBS device can receive an interrupt after request_irq but before dibs_dev_add initializes dibs lock. The ISM interrupt handler takes this lock unconditionally on entry, so a GID event in this window can make the kernel operate on an uninitialized spinlock and may cause a crash, warning, BUG, or deadlock. For the CVSS the PR:N is used in the paranoid interpretation because an attacker in a peer or adjacent ISM environment may not need privileges on the victim host if they can cause the relevant GID event during probe. The issue is not Internet reachable and requires a narrow timing window during device initialization. Impact is denial of service only because the patch supports an uninitialized lock and interrupt race, but does not show UAF, OOB access, information disclosure, or a write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Manual review recommended only to confirm whether GID events can be attacker-influenced in the deployed ISM environment (with actual score 1)  SKIP CVE-2026-74617 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	LOCK INIT SIMPLEFIX HARDWARE LINUS  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like. Manual review recommended only to confirm whether GID events can be attacker-influenced in the deployed ISM environment**

## 2. Signal breakdown

Paranoid signals:

* Firmware-mediated external influence: +1
  A GID event interrupt can occur after `request_irq()` and before `dibs_dev_add()`, and such an event may be influenced by the ISM peer or adjacent device environment.

* Reliable kernel crash / strong DoS: +1
  `ism_handle_irq()` takes `dibs->lock` unconditionally. If the spinlock has not been initialized yet, this can plausibly cause a WARN, BUG, crash, or deadlock.

* Hard or unreliable race / special timing required: -1
  The vulnerable window is narrow and exists only during device probe between IRQ registration and `dibs_dev_add()`.

* Rare / hardware-specific condition: -1
  The issue is tied to DIBS / ISM hardware-specific initialization and interrupt behavior, not a broad default kernel path.

Conservative interpretation:

* Requires admin/root/device-management action: -2
  Reliably entering the window normally requires device probe, driver load, or device initialization controlled by privileged host operations.

* DoS concern: +1
  The main realistic impact is crash or lock failure.

* Timing and rare hardware penalties reduce the conservative score to the floor.

No points awarded for:

* Generic memory corruption
  The patch shows an uninitialized lock initialization-order bug, not UAF, OOB write, double-free, type confusion, or controlled overwrite.

* Privilege escalation plausible
  No reclaim, object replacement, callback control, refcount abuse, or write primitive is shown.

* Confidentiality or integrity impact
  The patch supports availability impact only.

## 3. Reachability analysis

The conservative trigger requires privileged local control over device probing or driver initialization. The paranoid trigger assumes that a peer or adjacent ISM environment can cause a GID event during the short initialization window after `request_irq()` but before `dibs_dev_add()` initializes the lock. This is not Internet reachable and not a common network packet-processing path. Namespaces or containers do not obviously lower the required privileges because the affected path is hardware and driver initialization, not an ordinary unprivileged syscall interface.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like kernel DoS issue rather than an Important-class vulnerability. The theoretical concern is an interrupt-time race on an uninitialized synchronization primitive, but the realistic evidence points to crash, warning, BUG, or deadlock only. There is no supported memory-corruption primitive beyond use of an uninitialized spinlock, and no practical privilege-escalation path is shown by the patch.

## 5. One-sentence report phrase

A DIBS device may receive a GID event interrupt before `dibs->lock` is initialized, allowing the ISM interrupt handler to take an uninitialized spinlock and potentially crash or deadlock the kernel during a narrow device initialization window.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended to confirm whether GID event interrupts can be attacker-influenced in the target ISM deployment. If they cannot be influenced externally, this can likely be treated as a low-priority hardware-specific DoS fix.

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

Patch: dibs: initialise dibs->lock in dibs_dev_alloc()
Commit: fe79571f40434b257d68cbfb7b3ae93a794d8a11
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe79571f40434b257d68cbfb7b3ae93a794d8a11

Commit description:

dibs->lock is initialised by dibs_dev_add(), but a dibs device can
already take interrupts before that call: ism_probe() runs
ism_dev_init(), and hence request_irq(), before it calls
dibs_dev_add(). No client can have registered a dmb at that point, so
no dmb interrupt can occur, but a GID event interrupt can, and
ism_handle_irq() takes dibs->lock unconditionally on entry, before it
inspects anything else.

Initialise the lock in dibs_dev_alloc() instead, so that it is valid as
soon as a driver can publish the device to its interrupt handler.

Fixes: cc21191 ("dibs: Move data path to dibs layer")
Cc: stable@vger.kernel.org
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Hidayath Khan <hidayath@linux.ibm.com>
Link: https://patch.msgid.link/20260730124227.167829-1-hidayath@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/dibs/dibs_main.c
  include/linux/dibs.h

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=fe79571f40434b257d68cbfb7b3ae93a794d8a11

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

The original Linux kernel CVE announcement for CVE-2026-74617 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74617

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: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: 0
  Paranoid ActionableScore: 2

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).