[CVE-2026-74450][MODERATE 7.0] drm/amd/pm: fix pptable use-after-free

[CVE-2026-74450][MODERATE 7.0] drm/amd/pm: fix pptable use-after-free

[AL-KERNEL]

CVE: CVE-2026-74450
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amd/pm: fix pptable use-after-free
Commit: b628f2c6feb3a115ea72d3120a2bd94afc5163df
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b628f2c6feb3a115ea72d3120a2bd94afc5163df
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74450
Analysis date: Sat, 15 Aug 2026 08:57:00 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in the AMDGPU `pp_table` sysfs path can cause `amdgpu_get_pp_table()` to copy from a driver-owned power table after it has been replaced and freed, leading to a local use-after-free with possible kernel crash or stale memory disclosure.

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

The original Linux kernel CVE announcement for CVE-2026-74450 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74450

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.

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

CVE-2026-74450	MODERATE	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-200;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7';DESCR 'A use-after-free exists in the AMDGPU power management pp_table sysfs path because amdgpu_dpm_get_pp_table returns a driver-owned power table pointer after releasing adev pm mutex. The sysfs read path can then copy from that stale pointer while a concurrent pp_table write replaces and frees the allocation. This can crash the kernel and can also expose stale kernel memory through the sysfs read buffer if the freed allocation is reused before the copy. For the CVSS the PR:L is used for the paranoid score because reliable triggering may be possible for a local user or delegated GPU management service that can access the pp_table write path, although the default sysfs write permission is usually administrator-only. The issue is not network reachable. Impact is at least local denial of service and information disclosure, and worst-case use-after-free behavior should be reviewed for privilege escalation risk.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-74450 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER UAF HARDWARE MEMORY  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

This should not be auto-closed as an ordinary low-risk driver bug because it is a real kernel lifetime bug with a user-visible read path.

## 2. Signal breakdown

Conservative scoring:

* Generic memory corruption / UAF: +2
  The patch explicitly fixes a use-after-free where a driver-owned `pp_table` pointer can be freed by a concurrent write while the sysfs read path copies from it.

* Real lifetime corruption: +1
  The bug is caused by returning a pointer after dropping `adev->pm.mutex`, creating a stale pointer lifetime window.

* Confidentiality impact plausible: +1
  The stale pointer is copied into the sysfs read buffer, so reused freed memory could be exposed to userspace.

* Availability impact realistic: +1
  UAF during `memcpy()` can plausibly crash or trigger kernel memory safety checks.

* Hard race / timing required: -1
  The read must race with a concurrent `pp_table` write.

* Requires admin/root in typical deployments: -2
  Reliable triggering usually requires write access to the AMDGPU `pp_table` sysfs attribute, which is normally administrator-controlled.

Paranoid delta:

* Local lower-privilege trigger possibility: +1
  In environments with delegated GPU management, relaxed sysfs permissions, service accounts, or container/device delegation, the write side may be reachable below full host-root.

No privilege-escalation bonus is awarded because the patch shows stale read-after-free and possible disclosure/crash, but does not show attacker-controlled reclaim, controlled overwrite, callback control, type confusion, or arbitrary write.

## 3. Reachability analysis

The trigger is local through AMDGPU power-management sysfs attributes. A reader of `pp_table` can race with a writer that replaces and frees the underlying power table allocation. In default deployments, the write path is likely root/admin-only, so conservative scoring treats this as privileged local access. In some workstation, GPU-management, container, or service-account setups, access to GPU control files may be delegated, which supports the higher paranoid score. The issue is not network reachable.

Call-site confidence: high. The patch includes both the helper and the sysfs caller that previously copied from the returned pointer after the mutex was released.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because it is a concrete kernel UAF with a userspace copy-out path. Realistic exploitation evidence mainly supports local DoS and possible kernel memory disclosure. Privilege escalation remains only a review concern, not a demonstrated primitive, because there is no shown attacker-controlled reclaim or write-after-free path. Overall this is an Actionable Moderate and should receive manual review.

## 5. One-sentence report phrase

A race in the AMDGPU `pp_table` sysfs path can cause `amdgpu_get_pp_table()` to copy from a driver-owned power table after it has been replaced and freed, leading to a local use-after-free with possible kernel crash or stale memory disclosure.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real kernel UAF with a userspace-visible copy path. Even though default triggering likely requires admin-level sysfs write access, delegated GPU-management environments may reduce the practical privilege requirement.

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

Patch: drm/amd/pm: fix pptable use-after-free
Commit: b628f2c6feb3a115ea72d3120a2bd94afc5163df
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b628f2c6feb3a115ea72d3120a2bd94afc5163df

Commit description:

amdgpu_dpm_get_pp_table() returns a pointer to a driver-owned power table
after dropping adev->pm.mutex. The sysfs path then copies from that pointer.
A concurrent pp_table write can replace and free the allocation during the
copy, causing a use-after-free.

Change the DPM interface to copy into caller-provided storage while the mutex
is held. Keep the size-only query for attribute discovery without exposing
the driver-owned pointer.

Fixes: 1684d3b ("drm/amd/amdgpu: change pptable output format from ASCII to binary")
Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f6eed7a )
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/pm/amdgpu_dpm.c
  drivers/gpu/drm/amd/pm/amdgpu_pm.c
  drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h

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=b628f2c6feb3a115ea72d3120a2bd94afc5163df

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

The original Linux kernel CVE announcement for CVE-2026-74450 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74450

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:L/I:N/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: 3
  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).