[CVE-2026-80659][LOW] mmc: vub300: defer reset until cmd_mutex is unlocked

[CVE-2026-80659][LOW] mmc: vub300: defer reset until cmd_mutex is unlocked

[AL-KERNEL]

CVE: CVE-2026-80659
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: mmc: vub300: defer reset until cmd_mutex is unlocked
Commit: 8672b8bdbd2063b3fcbd75f729e4706fcdad2257
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8672b8bdbd2063b3fcbd75f729e4706fcdad2257
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80659
Analysis date: Fri, 28 Aug 2026 06:44:41 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80659 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80659

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: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-80659	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	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-667;*CWE-833;CWE-755;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A deadlock can occur in the vub300 MMC driver when a command response timeout causes __vub300_command_response() to call usb_reset_device() while vub300_cmndwork_thread() still holds cmd_mutex. The USB reset path can re enter the driver through vub300_pre_reset() and try to take the same mutex again, causing a same task recursive lock acquisition and leaving the command worker stuck. For the CVSS the PR:L is used because practical triggering requires local ability to drive I/O or interact with the affected device path, but not necessarily full administrator privileges in all deployments. The issue is not network reachable and depends on timeout/reset conditions for a VUB300 USB MMC device. Impact is denial of service through a hung MMC request or device I/O path, with no evidence of memory corruption or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	LOCK DEADLOCK WARNONLY HARDWARE LINUS 	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

1. ActionableScore
* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

2. Signal breakdown
* Local unprivileged trigger: +1 in the paranoid interpretation, because a local user may be able to issue MMC I/O through the affected device path.
* Reliable kernel crash / strong DoS: +1 only as a bounded device-path DoS, because the demonstrated failure is a recursive mutex deadlock in the worker path, not memory corruption.
* Hard or unreliable trigger condition: -1, because the issue depends on a command timeout followed by USB reset re-entry.
* Physical-only or rare hardware-only condition: -2, because the affected driver is for the VUB300 USB-to-SD/SDIO/MMC device and requires that specific hardware or an equivalent test setup.
* No memory corruption signal applies. The patch shows recursive locking and deadlock, not UAF, OOB access, double free, type confusion, refcount misuse, or attacker-controlled overwrite.
* No confidentiality or integrity signal applies. The supported impact is availability only.

3. Reachability analysis
The bug is triggerable only on systems using the vub300 MMC USB driver. A local process may be able to generate MMC commands through normal I/O, but the vulnerable path requires a command response timeout and a synchronous USB reset while cmd_mutex is still held. A malicious or faulty physical USB device could make the timeout/reset path more reachable, but this is not network reachable and not a default broad kernel attack surface. Namespaces and containers do not materially improve reachability unless the container is given access to the affected block or MMC device.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like availability issue. The theoretical impact is a stuck command worker or hung device I/O path. The patch does not support privilege escalation, memory corruption, information disclosure, or cross-boundary access. The paranoid score stays low because even though the deadlock is real, exploitation depends on rare hardware and timeout/reset conditions.

5. One-sentence report phrase
A recursive locking deadlock in the vub300 MMC driver can occur when a command timeout triggers usb_reset_device() while cmd_mutex is still held, causing a local device I/O denial of service on systems using the affected VUB300 USB MMC hardware.

6. Manual review recommendation
NO MANUAL CHECK NEEDED
This is a device-specific locking DoS with no demonstrated memory corruption or privilege escalation primitive. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED.

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

Patch: mmc: vub300: defer reset until cmd_mutex is unlocked
Commit: 8672b8bdbd2063b3fcbd75f729e4706fcdad2257
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8672b8bdbd2063b3fcbd75f729e4706fcdad2257

Commit description:

vub300_cmndwork_thread() holds cmd_mutex while it sends a command and
waits for the command response.  If the response wait times out,
__vub300_command_response() kills the command URBs and then synchronously
resets the USB device through usb_reset_device().

That reset path re-enters the driver through vub300_pre_reset(), which
also takes cmd_mutex.  The worker therefore tries to acquire the same
mutex recursively while it is still holding it from the command path.

This issue was found by our static analysis tool and then manually
reviewed against the current tree.

The grounded PoC kept the real worker and timeout/reset carrier:

  vub300_cmndwork_thread()
  __vub300_command_response()
  usb_lock_device_for_reset()
  usb_reset_device()
  vub300_pre_reset()

Lockdep reported the same-task recursive acquisition on cmd_mutex:

  WARNING: possible recursive locking detected
  ... (&test_vub300.cmd_mutex) ... at: usb_reset_device... [vuln_msv]
  ... (&test_vub300.cmd_mutex) ... at: vub300_cmndwork_thread+0x12/0x20 [vuln_msv]
  Workqueue: vub300_cmd_wq vub300_cmndwork_thread [vuln_msv]
  *** DEADLOCK ***

Return a flag from __vub300_command_response() when the timeout path needs
a device reset, then perform the reset after vub300_cmndwork_thread() has
cleared the in-flight command state and dropped cmd_mutex.  The reset is
still attempted before mmc_request_done(), preserving the existing request
completion ordering while avoiding the recursive lock.

Fixes: 88095e7 ("mmc: Add new VUB300 USB-to-SD/SDIO/MMC driver")
Cc: stable@vger.kernel.org
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Signed-off-by: Ulf Hansson <ulfh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/mmc/host/vub300.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=8672b8bdbd2063b3fcbd75f729e4706fcdad2257

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

The original Linux kernel CVE announcement for CVE-2026-80659 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80659

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:L/UI:N/S:U/C:N/I:N/A:L
  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: 1
  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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).