[CVE-2026-98208][LOW] mmc: sdio_uart: fix xmit_fifo leak when the port table is full

[CVE-2026-98208][LOW] mmc: sdio_uart: fix xmit_fifo leak when the port table is full

[AL-KERNEL]

CVE: CVE-2026-98208
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: mmc: sdio_uart: fix xmit_fifo leak when the port table is full
Commit: 9e992d59138fcfaa4bad7cc0750265b0a8bca100
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e992d59138fcfaa4bad7cc0750265b0a8bca100
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98208
Analysis date: Fri, 09 Oct 2026 04:59:29 -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-2026-98208 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98208

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-2026-98208	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98208 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';*CWE-401;*CWE-772;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '2.3';DESCR 'sdio_uart_add_port can retain an allocated transmit FIFO when every UART_NR table slot is occupied and registration returns EBUSY. The demonstrated primitive is a persistent kernel memory leak on the failed device probe path, with no evidence of UAF, out of bounds access, information disclosure, or memory corruption. For the CVSS the PR:H is selected because reliably reaching and repeating this path normally requires administrative control over SDIO device probing or driver lifecycle operations. The issue is not network reachable. Repeated failures could gradually consume kernel memory, but the patch does not establish that an unprivileged actor can repeat the operation or cause rapid host wide exhaustion. Impact is therefore limited to a low availability risk rather than an immediate system crash or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	INIT SIMPLEFIX LEAK ERRORPATH LINUS 	-	-	checked

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

ActionableScore=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
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 Concrete persistent kernel resource leak. `xmit_fifo` is allocated before slot acquisition and is permanently lost when `sdio_uart_add_port()` returns `-EBUSY`.
* No generic resource-exhaustion point. Repeatable accumulation, rapid memory exhaustion, and host-wide availability impact are not established.
* No B5-R signal. There is no heap OOB write, retry-accumulated offset, corrupted descriptor consumption, or related corruption primitive.
* No UAF, double release, invalid dereference, arbitrary write, disclosure, or integrity violation is established.
* No crash or strong DoS point. The demonstrated consequence is one leaked FIFO per reached failure path.
* No privilege penalty. Host-admin control is plausible for driver lifecycle operations but is not positively established for every possible probe path.
* No hardware penalty. SDIO UART hardware is required, but the evidence is insufficient to classify it as rare physical-only exposure under the strict negative-evidence rule.

3. Reachability analysis

The failure requires all `UART_NR` table slots to be occupied and another SDIO UART port probe to reach `sdio_uart_add_port()`. The supplied evidence does not establish that an ordinary user can instantiate devices, force probes, or repeat the failure. It also does not conclusively prove that host-admin-equivalent privilege is required because probing may follow hardware discovery automatically. The operation is not namespace-scoped, and no network or remote trigger exists. There is no race requirement.

4. Primitive and severity interpretation

The exact primitive is a missing `kfifo_free()` on an `-EBUSY` error path, producing a persistent but individually bounded kernel heap leak. It is not a post-lifetime access because the leaked FIFO is never used through a dangling reference. It is also not a repeated release, memory corruption, or corrupted-state consumption case.

`PrimitiveClass=NONE` is appropriate because no corruption, UAF, ownership violation, or authorization bypass exists. The practical consequence is gradual resource retention only if the failed probe can be repeated. Important-grade impact is unsupported, and automatic downgrade is safe.

5. One-sentence report phrase

A failed SDIO UART port registration can leak its transmit FIFO when the port table is full, but no memory corruption, crash, or demonstrated unprivileged resource-exhaustion path is established.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a concrete but low-impact error-path resource leak with no established B5-R OOB write, security boundary, or strong availability consequence.

7. Call-site confidence

Call-site confidence: high

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

Patch: mmc: sdio_uart: fix xmit_fifo leak when the port table is full
Commit: 9e992d59138fcfaa4bad7cc0750265b0a8bca100
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e992d59138fcfaa4bad7cc0750265b0a8bca100

Commit description:

sdio_uart_add_port() allocates the transmit fifo before claiming a
slot in sdio_uart_table[].  When all UART_NR slots are taken, it
returns -EBUSY with the fifo still allocated, but the probe error
path only kfree()s the port, leaking the transmit fifo.

Free the fifo in the failure path of sdio_uart_add_port() itself so
the function retains nothing on error.

Fixes: 8b197a5 ("sdio_uart: Use kfifo instead of the messy circ stuff")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulfh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/mmc/core/sdio_uart.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=9e992d59138fcfaa4bad7cc0750265b0a8bca100

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

The original Linux kernel CVE announcement for CVE-2026-98208 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98208

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:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 2.3

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