[CVE-2026-68380][IMPORTANT] accel/amdxdna: Fix use-after-free of mm_struct in job scheduler [ Upstream

[CVE-2026-68380][IMPORTANT] accel/amdxdna: Fix use-after-free of mm_struct in job scheduler [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68380
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: accel/amdxdna: Fix use-after-free of mm_struct in job scheduler [ Upstream
Commit: 6875ee2bef48f5d9f045d81a8a4d68893f768a8a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6875ee2bef48f5d9f045d81a8a4d68893f768a8a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68380
Analysis date: Mon, 10 Aug 2026 13:37:30 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local use-after-free in the amdxdna job scheduler can occur because command submission stores `current->mm` without taking an `mm_struct` reference, allowing a later scheduler worker to dereference freed memory and potentially crash the kernel or require manual review for privilege-escalation risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68380 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68380

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: IMPORTANT
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-2026-68380	IMPORTANT	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-825;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use-after-free can occur in the amdxdna job scheduler because amdxdna_cmd_submit stores current mm in job mm without holding a structural reference. The scheduler worker can later dereference job mm after the submitting task exits and its mm_struct has been freed. For the CVSS the PR:L is used for the paranoid score because reliable triggering requires local code execution with access to the amdxdna accel device, which may be available to non root users through render or accelerator device permissions rather than full administrator rights. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to UAF on a core memory management object, so manual review is required.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-68380 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	UAF KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Local unprivileged trigger: +1. Triggering appears possible from a local process that can submit jobs to the amdxdna accelerator device.
* Generic memory corruption: +2. The patch explicitly fixes a use-after-free of `mm_struct`.
* Real lifetime corruption: +1. `job->mm` outlives the submitting task without `mmgrab()`, and is later used by a scheduler worker.
* Reliable kernel crash / strong DoS: +1. Dereferencing a freed `mm_struct` from a worker thread can plausibly crash the kernel.
* Privileged kernel/device-management lifetime path: +1. The bug is in an accelerator job scheduler and involves lifetime of a core memory-management object.
* Rare hardware / device-specific exposure: -1. Exposure depends on AMD XDNA hardware, driver availability, and device node permissions.
* Weak LPE concern, paranoid only: +1. UAF of `mm_struct` is a high-value lifetime bug, but no controlled reclaim, overwrite, callback control, or type confusion is demonstrated.
* Confidentiality/integrity plausible, paranoid only: +1. Theoretical C/I impact is defensible due to UAF on `mm_struct`, but evidence supports DoS more strongly than practical LPE.

## 3. Reachability analysis

The bug is locally reachable through the amdxdna command submission path. A process submits a job, `amdxdna_cmd_submit()` stores `current->mm` in `job->mm`, and the DRM scheduler worker later accesses that pointer after the original task may have exited. No network reachability is indicated.

Privileges depend on device node policy. Conservative handling assumes a local user with access to the accelerator device, which may be granted through render or accelerator groups rather than full root. Containers or reduced-privilege service accounts could matter if the device node is passed through. The path is not broadly default-exposed on all Linux systems because it requires AMD XDNA hardware and the amdxdna driver.

Call-site confidence: high. The commit explicitly states that `aie2_sched_job_run()` accesses `job->mm` from the scheduler worker, and the patch adds `mmgrab()` and matching `mmdrop()` on cleanup/error paths.

## 4. Severity interpretation

This is not an ordinary Moderate cleanup issue. It is an explicit asynchronous lifetime bug causing UAF of `mm_struct`, which is more serious than a NULL dereference or resource leak.

Realistically, the clearest impact is local kernel crash or system instability. The paranoid interpretation treats it as an Important candidate because `mm_struct` is security-sensitive kernel state and UAF bugs in scheduler/device paths can sometimes become privilege-escalation primitives. However, the patch does not demonstrate controlled reclaim, attacker-chosen replacement, arbitrary write, or callback control, so practical LPE remains unproven.

## 5. One-sentence report phrase

A local use-after-free in the amdxdna job scheduler can occur because command submission stores `current->mm` without taking an `mm_struct` reference, allowing a later scheduler worker to dereference freed memory and potentially crash the kernel or require manual review for privilege-escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: explicit UAF of `mm_struct` in an asynchronous worker path. Even though practical exploitation beyond DoS is not demonstrated, the object type and lifetime pattern are important enough to avoid auto-closure.

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

Patch: accel/amdxdna: Fix use-after-free of mm_struct in job scheduler [ Upstream
Commit: 6875ee2bef48f5d9f045d81a8a4d68893f768a8a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6875ee2bef48f5d9f045d81a8a4d68893f768a8a

Changed files:
  drivers/accel/amdxdna/amdxdna_ctx.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=6875ee2bef48f5d9f045d81a8a4d68893f768a8a

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

The original Linux kernel CVE announcement for CVE-2026-68380 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68380

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:L/I:L/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: 5
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).