[CVE-2026-68245][MODERATE 7.0] drm/amdgpu: fix lifetime issue of amdgpu_vm_get_task_info_pasid()

[CVE-2026-68245][MODERATE 7.0] drm/amdgpu: fix lifetime issue of amdgpu_vm_get_task_info_pasid()

[AL-KERNEL]

CVE: CVE-2026-68245
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu: fix lifetime issue of amdgpu_vm_get_task_info_pasid()
Commit: fe16a7e5336ae888751984e30c451fbf7cfa5df7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe16a7e5336ae888751984e30c451fbf7cfa5df7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68245
Analysis date: Mon, 10 Aug 2026 20:34:00 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local AMDGPU user may race PASID VM lookup against VM teardown so that `amdgpu_vm_get_task_info_pasid()` dereferences a VM pointer after its xarray lifetime protection has ended, creating a UAF candidate and at least a kernel crash risk.

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

The original Linux kernel CVE announcement for CVE-2026-68245 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68245

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 7.0
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-2026-68245	MODERATE	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:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A lifetime race in amdgpu_vm_get_task_info_pasid can leave a VM pointer valid only while the PASID xarray lock is held, but the old code dereferenced vm task_info after that lock was released. A local user able to exercise AMDGPU DRM paths could race PASID lookup against VM teardown or modification, creating a use-after-free candidate and at least a kernel crash scenario. For the CVSS the PR:L is used because practical triggering requires local code execution with access to the GPU device or render node, but not full administrative privileges. The issue is not network reachable and requires a timing window, so AC:H is appropriate. Impact is at least local denial of service via kernel crash and in the paranoid case may allow confidentiality or integrity impact due to kernel object lifetime corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	MAYBE	SIMPLEFIX HARDWARE  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. AMDGPU DRM render or device nodes are commonly reachable by local users in desktop or GPU compute deployments.
* Memory corruption, weak or indirect corruption candidate: +1. The patch fixes a VM pointer lifetime race where a pointer loaded from the PASID xarray was dereferenced after the protecting lock was dropped.
* Real lifetime corruption: +1. This is a use-after-unlock lifetime bug and a plausible stale pointer or UAF candidate.
* Reliable kernel crash / strong DoS: +1. A stale `vm` pointer dereference through `vm->task_info` can plausibly crash the kernel.
* Broad/common subsystem exposure: +1. DRM render-node access is common on systems with AMD GPUs.
* Hard or unreliable race / special timing required: -1. Exploitation requires racing PASID lookup against VM teardown or modification.

Conservative total: 4

Paranoid additional signal:

* Weak LPE concern: +1. The stale pointer is used to access task-info lifetime/refcounted state, so object reuse could theoretically produce more than a crash, but no controlled reclaim, overwrite, callback control, or reliable object replacement is shown.

Paranoid total: 5

## 3. Reachability analysis

A local user or local process with access to AMDGPU DRM paths may be able to trigger the affected lookup path. Full root privileges are not inherently required if the relevant `/dev/dri` node is exposed to the user or to a container.

This is not network reachable. Containers matter only when GPU device nodes are passed through or delegated. The path is hardware and driver dependent, so it applies mainly to systems using AMDGPU, but those systems often expose render nodes to non-root users.

Realistic exploitation requires a timing window between PASID xarray lookup and VM teardown or modification. That makes the bug harder than a direct ioctl crash, but the lifetime pattern is security-relevant enough for manual review.

## 4. Severity interpretation

This is not an ordinary low-priority cleanup. It is a local lifetime race in a kernel driver object path and should be treated as at least an actionable Moderate.

Realistically demonstrated impact is kernel crash or local DoS. Theoretical impact may extend toward privilege escalation because the bug is a stale kernel object lifetime issue, but the patch does not show attacker-controlled reclaim, arbitrary write, callback hijack, or a reliable type-confusion primitive. Therefore the conservative score stays borderline, while the paranoid score reaches Actionable Moderate.

## 5. One-sentence report phrase

A local AMDGPU user may race PASID VM lookup against VM teardown so that `amdgpu_vm_get_task_info_pasid()` dereferences a VM pointer after its xarray lifetime protection has ended, creating a UAF candidate and at least a kernel crash risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a kernel lifetime race with a plausible stale pointer or UAF primitive in a locally reachable DRM/GPU path. It should not be auto-closed without confirming call paths, object lifetime rules, and whether local users can reliably reach the affected PASID lookup path.

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

Patch: drm/amdgpu: fix lifetime issue of amdgpu_vm_get_task_info_pasid()
Commit: fe16a7e5336ae888751984e30c451fbf7cfa5df7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe16a7e5336ae888751984e30c451fbf7cfa5df7

Commit description:

The vm pointer returned from amdgpu_vm_get_vm_from_pasid() is only
valid while the lock is still being held. Once xa_unlock_irqrestore is
called and returned, the pointer is no longer under lock and is subject
to modification. Since, the caller still dereferences vm->task_info in
amdgpu_vm_get_task_info_vm() after the lock is removed, this causes a
use after unlock problem.

Remove the lifetime issue present in amdgpu_vm_get_task_info_pasid()
through removing the amdgpu_vm_get_vm_from_pasid() function from
amdgpu_vm.c and making the relevant code inline to hold the lock while
it is still in use.

Signed-off-by: Shahyan Soltani <shahyan.soltani@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 9d01579 )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.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=fe16a7e5336ae888751984e30c451fbf7cfa5df7

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

The original Linux kernel CVE announcement for CVE-2026-68245 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68245

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: 4
  Paranoid ActionableScore: 5

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 7.0

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).