[CVE-2026-64485][LOW] ALSA: compress: Fix task creation error unwind

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

CVE: CVE-2026-64485
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ALSA: compress: Fix task creation error unwind
Commit: b27a75d42044d9d4709095617730b91b1c4af423
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b27a75d42044d9d4709095617730b91b1c4af423
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64485
Analysis date: Sat, 25 Jul 2026 09:16:27 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
ALSA compress task creation could leak driver allocated resources when task_create() succeeded but later DMA buffer validation or file descriptor allocation failed, allowing a local user with access to the compress offload device to cause resource exhaustion DoS.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64485 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64485

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64485	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-393;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'ALSA compress task creation could leak driver allocated resources when task_create succeeded but later validation of DMA buffers or file descriptor allocation failed. The core cleanup path freed the common task wrapper but skipped the driver task_free() callback, so repeated failed TASK_CREATE operations could accumulate unreleased driver resources. For the CVSS the PR:L is used because triggering requires local access to an ALSA compress offload device or a process context allowed to issue the relevant ioctl, but does not normally require full administrator privileges. The issue is not network reachable. Impact is local denial of service through resource exhaustion, with no supported evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	INIT LEAK UAF DMAorINTERRUPT HARDWARE LINUS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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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. Triggering requires local access to an ALSA compress offload device and the relevant TASK_CREATE ioctl path, but not necessarily full root privileges.
* Availability impact realistic: +1 in paranoid scoring only. Repeated failed task creation may leak driver resources and could eventually cause resource exhaustion.
* No generic memory corruption: +0. The patch fixes missing driver task_free() on error unwind and incorrect retval preservation. It does not show UAF, OOB write, double free, type confusion, arbitrary write, or stale callback use.
* No privilege escalation plausible: +0. There is no supported LPE primitive.
* No confidentiality or integrity impact: +0. The bug is a resource leak and error reporting issue.
* No remote reachability: +0. This is a local device ioctl path.
* No high-control device API bonus: +0. ALSA device object configuration alone is not enough, and the patch does not show attacker control over lifetime reuse, callback targets, DMA mappings, page ownership, or allocator shaping.
* Rare or device-dependent exposure: possible -1, but not applied in the main score because ALSA device nodes are ordinary local interfaces when present.

## 3. Reachability analysis

The bug can be triggered by a local process that can open and use the affected ALSA compress offload device. Typical systems restrict such devices through udev permissions, audio groups, seat/session policy, or container device passthrough. It is not network reachable. Namespaces do not normally make the path reachable unless the device node is deliberately exposed into a container. The affected feature is hardware and driver dependent, so exposure is narrower than a core syscall or common networking path.

Call-site confidence: high. The provided patch includes the relevant error paths in snd_compr_task_new() and shows that failures after task_create() previously skipped stream->ops->task_free().

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local resource leak, not an Important-class kernel vulnerability. The realistic impact is local denial of service through repeated resource leakage if an attacker can repeatedly force the post-task_create failure paths. Theoretical impact does not extend to memory corruption or privilege escalation based on this patch, because the fixed bug is missing cleanup and wrong error propagation, not stale object reuse or attacker-controlled overwrite.

## 5. One-sentence report phrase

ALSA compress task creation could leak driver allocated resources when task_create() succeeded but later DMA buffer validation or file descriptor allocation failed, allowing a local user with access to the compress offload device to cause resource exhaustion DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be handled as a low-priority resource leak fix unless the affected product exposes ALSA compress offload devices broadly to untrusted users or a specific driver task_create() implementation is known to allocate scarce non-reclaimable resources.

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

Patch: ALSA: compress: Fix task creation error unwind
Commit: b27a75d42044d9d4709095617730b91b1c4af423
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b27a75d42044d9d4709095617730b91b1c4af423

Commit description:

snd_compr_task_new() allocates the driver task before validating the
returned DMA buffers and reserving file descriptors. When either of
those later steps fails, the core frees its task wrapper and DMA-buffer
references without calling the driver's task_free() callback. Any
driver resources allocated by task_create() are therefore leaked.

The dual-fd allocation path also jumps to cleanup without storing the
negative get_unused_fd_flags() result in retval. Since retval still
contains the successful task_create() return value, TASK_CREATE can
incorrectly report success although the task was discarded.

Preserve the fd allocation errors and call task_free() when failure
occurs after a successful task_create() callback.

Fixes: 0417715 ("ALSA: compress_offload: introduce accel operation mode")
Fixes: 3d3f43f ("ALSA: compress_offload: improve file descriptors installation for dma-buf")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
Link: https://patch.msgid.link/20260615-alsa-compress-task-unwind-v1-1-39e8ad3ddb27@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/core/compress_offload.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=b27a75d42044d9d4709095617730b91b1c4af423

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

The original Linux kernel CVE announcement for CVE-2026-64485 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64485

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:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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).