[CVE-2026-89441][MODERATE REGULAR] mmc: via-sdmmc: cancel card-detect work on remove

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

CVE: CVE-2026-89441
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: mmc: via-sdmmc: cancel card-detect work on remove
Commit: f7ff3027ef004a331ef911a4886f12bc2e996037
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f7ff3027ef004a331ef911a4886f12bc2e996037
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89441
Analysis date: Fri, 11 Sep 2026 18:53:40 -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.

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

The original Linux kernel CVE announcement for CVE-2026-89441 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89441

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-2026-89441	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89441 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-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use after free can occur in the via sdmmc remove path because carddet_work may already be queued when via_sd_remove() disables the interrupt and frees the IRQ. The delayed card detect worker can later recover the host object with container_of() and dereference its MMIO base after the host has been freed, which can cause a kernel crash or other memory corruption symptoms. For the CVSS the PR:L is used in the paranoid score because a delegated local service, container root, or restricted admin path may be able to trigger device removal or driver unbind while card detect work is pending. The issue is not network reachable and requires local control over the device lifecycle or a local hotplug style race. Impact is at least denial of service via kernel crash, and in the worst case may affect confidentiality and integrity because the primitive is a kernel use after free and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	YES	UAF DMAorINTERRUPT HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::

No floor or cap changed the score.

2. Signal breakdown

Positive signals:

* +2 Real UAF / lifetime violation: queued `carddet_work` can run after `via_sd_remove()` returns, recover `sdhost` through `container_of()`, and dereference state that may already have been freed.
* +1 Reliable kernel crash / strong DoS: stale work touching freed driver state and MMIO-related fields can plausibly cause an Oops or kernel crash.

Negative or non-awarded signals:

* No controlled reclaim demonstrated.
* No arbitrary or directed kernel write demonstrated.
* No concrete repeated release/refcount mutation on the same dangling reference.
* No structured stale-object leverage awarded because the stale path appears to be an async remove/cleanup path and the demonstrated effect is stale dereference/DoS.
* No C/I bonus awarded merely because UAF theoretically could corrupt reused memory.
* No remote reachability established.
* No extra availability point awarded because the same crash is already counted.
* No host-admin penalty applied in the numeric score because the supplied evidence does not fully resolve whether all possible triggering paths are strictly host-admin-only, although reliable software-triggered removal is likely privileged.

Repeated release/refcount check:

* First release can end lifetime: not established as a repeated release pattern.
* Exact same reference survives to second lifetime mutation: not established.
* Second operation is a real lifetime/refcount mutation: no.
* Concrete repeated release/refcount +1: not awarded.
* Paranoid repeated-refcount leverage +1: not awarded.
* FLOOR 5: not applied.

3. Reachability analysis

The vulnerable function is in the PCI MMC host driver remove path. A reliable software trigger normally appears to require local control over driver/device lifecycle, such as driver unbind, module removal, or PCI device removal, which is commonly host-admin-equivalent. However, the input also involves asynchronous card-detect work queued by an interrupt, and the supplied snippet does not fully prove the complete attacker privilege boundary for all deployment models.

No namespace-scoped capability path is established. This is not a network-reachable issue. There is no evidence that an ordinary unprivileged user can trigger the full sequence. There is no evidence of BPF, KVM, netns, or container-scoped reachability. The issue is hardware and driver specific, but no separate rare-hardware penalty is applied solely because it is a driver.

Race/timing is present in the sense that already queued work must survive into remove teardown, but no separate hard-race penalty is applied because the patch directly describes the missing synchronization.

4. Primitive and severity interpretation

The exact primitive is an async workqueue lifetime bug: `carddet_work` may outlive the `sdhost` object and dereference freed driver state after `via_sd_remove()` returns. This is a real Class B UAF, but it appears constrained to remove/teardown processing of a fixed driver context.

The demonstrated consequence is local DoS through kernel crash or stale MMIO-state access. Stronger outcomes such as privilege escalation are speculative because the patch does not show controlled reclaim, attacker-shaped replacement object contents, callback control, arbitrary read/write, or a second lifetime/refcount mutation.

PrimitiveClass is CLASS_B because a real kernel lifetime violation exists. ImportantCandidate is NO because the visible primitive is constrained and crash-oriented. AutoDowngradeAllowed is YES because no meaningful unresolved exploitation leverage beyond the UAF crash path is established.

5. One-sentence report phrase

A queued via-sdmmc card-detect work item can run after device removal and dereference freed host/MMIO state, causing a local driver-lifecycle UAF with kernel DoS impact.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: real UAF is established, but current evidence supports a constrained teardown/async-work crash path rather than a strong exploitation primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: mmc: via-sdmmc: cancel card-detect work on remove
Commit: f7ff3027ef004a331ef911a4886f12bc2e996037
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f7ff3027ef004a331ef911a4886f12bc2e996037

Commit description:

Disabling the device interrupt and freeing the IRQ prevents new card-detect
work from being queued, but carddet_work already queued by the handler can
still run after via_sd_remove() returns. via_sdc_card_detect() recovers the
host through container_of() and dereferences its MMIO base; once remove()
returns the host can be freed, so that work would touch freed memory.

Cancel carddet_work after freeing the IRQ and before cancelling
finish_bh_work, which the card-detect handler can also queue. carddet_work
can re-enable the interrupt through via_reset_pcictrl(); mask it again
afterwards.

This issue was found by an in-house static analysis tool and confirmed by
manual code review.

Fixes: f0bf7f6 ("mmc: Add new via-sdmmc host controller driver")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.6
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
Signed-off-by: Ulf Hansson <ulfh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/mmc/host/via-sdmmc.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=f7ff3027ef004a331ef911a4886f12bc2e996037

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

The original Linux kernel CVE announcement for CVE-2026-89441 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89441

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: 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).