[CVE-2026-53145][IMPORTANT] drm/gem: Try to fix change_handle ioctl, attempt 4

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

CVE: CVE-2026-53145
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: drm/gem: Try to fix change_handle ioctl, attempt 4
Commit: c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53145
Analysis date: Fri, 26 Jun 2026 04:48:36 -0400
ActionableScore: 8
ActionableScore lower bound: 7
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local DRM render node user can race GEM_CHANGE_HANDLE with GEM_CLOSE and corrupt GEM object handle lifetime, creating a plausible UAF or stale object reference condition with kernel crash and possible privilege escalation impact.

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

The original Linux kernel CVE announcement for CVE-2026-53145 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53145

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-2026-53145	IMPORTANT	CHECK	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-362;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in the DRM GEM_CHANGE_HANDLE ioctl can corrupt GEM object handle lifetime because gem_close and change_handle can operate concurrently on the same idr slots. The vulnerable path swaps the old and new handles with staged idr_replace and idr_remove operations, and incorrect ordering or error handling can leave stale entries or allow a concurrent close to steal the only object reference. This is a plausible use-after-free or reference lifetime corruption issue in kernel DRM GEM objects rather than a simple warning or resource leak. For the CVSS the PR:L is used because a local process with access to a DRM render node can call the ioctl without full administrative privileges. The issue is not network reachable and requires local execution with access to the DRM device. Impact is at least local denial of service via kernel crash and in the worst case may allow confidentiality and integrity impact through memory corruption, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)  SKIP CVE-2026-53145  SKIP The Fixes patch not applied yet, so unlikely that actual: dc366607c41c45fd0ae6f3db090f31dd611b644a YES  NO NO unknown 	MAYBE	OOB LOCK INIT RACE ERRORPATH HARDWARE TEST SYZBOT  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=7

## 1. ActionableScore

* Conservative score: 7
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Local unprivileged trigger: +1
  The ioctl is marked DRM_RENDER_ALLOW, so a local process with access to a DRM render node can reach it without full root privileges.

* Generic memory corruption, strong corruption primitive candidate: +2
  The patch context describes a race between GEM_CHANGE_HANDLE and GEM_CLOSE around idr slots and GEM object lifetime. A concurrent close may steal the inherited object reference, making UAF or stale object lifetime corruption plausible.

* Real lifetime corruption: +1
  The bug is specifically about object reference ownership, idr replacement, stale handle state, and concurrent handle deletion.

* Weak to moderate privilege escalation plausibility: +1 conservative, +2 paranoid
  Conservative scoring treats this as plausible but not demonstrated LPE. Paranoid scoring raises this because DRM GEM UAF and object lifetime bugs have historically been security sensitive, and the ioctl was disabled for security reasons.

* Reliable kernel crash / strong DoS: +1
  syzbot involvement and the race around object lifetime make kernel crash a realistic outcome.

* Broad/default/common subsystem exposure: +1
  DRM render nodes are common on desktop, workstation, and GPU enabled server systems.

* Confidentiality impact plausible: +1
  Plausible UAF or stale GEM object access may expose kernel or graphics memory state, but no concrete leak primitive is shown.

* Integrity impact plausible: +1
  GEM object lifetime corruption may allow wrong object association or stale object manipulation, but no controlled write primitive is demonstrated.

* Hard or unreliable race / special timing required: -1
  The issue depends on racing GEM_CHANGE_HANDLE with GEM_CLOSE and hitting a narrow lifetime window.

## 3. Reachability analysis

A local process that can open the DRM device node and issue DRM render ioctls can potentially trigger the vulnerable path. This does not require network reachability. In typical deployments, access depends on device node permissions such as membership in video or render groups, logind ACLs, container GPU passthrough, or service account access to /dev/dri/renderD*. Containers can matter because GPU device passthrough may expose DRM render nodes to reduced privilege workloads. The path is not universally enabled on headless systems without DRM devices, but it is common where GPU acceleration is available.

## 4. Severity interpretation

This behaves above an ordinary Moderate because it is not merely a WARN or simple NULL dereference. The patch describes repeated failed attempts to fix a security race and ultimately disables the ioctl. The realistic demonstrated impact is local DoS or kernel crash. The theoretical but technically defensible higher impact is local privilege escalation or sensitive memory exposure through GEM object lifetime corruption. The conservative result is Actionable Moderate / Important candidate, and the paranoid result is Strong Important candidate.

## 5. One-sentence report phrase

A local DRM render node user can race GEM_CHANGE_HANDLE with GEM_CLOSE and corrupt GEM object handle lifetime, creating a plausible UAF or stale object reference condition with kernel crash and possible privilege escalation impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This needs manual review because the patch disables the ioctl for security reasons, the bug class is a race plus object lifetime corruption, and the plausible impact extends beyond ordinary DoS even though a concrete LPE primitive is not demonstrated in the patch.

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

Patch: drm/gem: Try to fix change_handle ioctl, attempt 4
Commit: c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd

Commit description:

[airlied: just added some comments on how to reenable]
On-list because the cat is out of the bag and we're clearly not good
enough to figure this out in private. The story thus far:

5e28b7b ("drm: Set old handle to NULL before prime swap in
change_handle") tried to fix a race condition between the gem_close and
gem_change_handle ioctls, but got a few things wrong:

- There's a confusion with the local variable handle, which is actually
  the new handle, and so the two-stage trick was actually applied to the
  wrong idr slot. 7164d78 ("drm/gem: fix race between
  change_handle and handle_delete") tried to fix that by adding yet
  another code block, but forgot to add the error handling. Which meant
  we now have two paths, both kinda wrong.

- dc36660 ("drm: Replace old pointer to new idr") tried to apply
  another fix, but inconsistently, again because of the handle confusion
  - this would be the right fix (kinda, somewhat, it's a mess) if we'd
  do the two-stage approach for the new handle. Except that wasn't the
  intent of the original fix.

We also didn't have an igt merged for the original ioctl, which is a big
no-go. This was attempted to address off-list in the original bugfix,
and amd QA people claimed the bug was fixed now. Very clearly that's not
the case. Here's my attempt to sort this out:

- Rename the local variable to new_handle, the old aliasing with
  args->handle is just too dangerously confusing.

- Merge the gem obj lookup with the two-stage idr_replace so that we
  avoid getting ourselves confused there.

- This means we don't have a surplus temporary reference anymore, only
  an inherited from the idr. A concurrent gem_close on the new_handle
  could steal that. Fix that with the same two-stage approach
  create_tail uses. This is a bit overkill as documented in the comment,
  but I also don't trust my ability to understand this all correctly, so
  go with the established pattern we have from other ioctls instead for
  maximum paranoia.

- Adjust error paths. I've tried to make the error and success paths
  common, because they are identical except for which handle is removed
  and on which we call idr_replace to (re)install the object again. But
  that made things messier to read, so I've left it at the more verbose
  version, which unfortunately hides the symmetry in the entire code
  flow a bit.

- While at it, also replace the 7 space indent with 1 tab.

And finally, because I flat out don't trust my abilities here at all
anymore:

- Disable the ioctl until we have the igt situation and everything else
  sorted out on-list and with full consensus.

v2:

Sashiko noticed that I didn't handle the error path for idr_replace
correctly, it must be checked with IS_ERR_OR_NULL like in
gem_handle_delete. So yeah, definitely should just the existing paths
1:1 because this is endless amounts of tricky.

Also add the Fixes: line for the original ioctl, I forgot that too.

Reported-by: DARKNAVY (@DarkNavyOrg) <vr@darknavy.com>
Signed-off-by: Simona Vetter <simona.vetter@ffwll.ch>
Fixes: dc36660 ("drm: Replace old pointer to new idr")
Cc: syzbot+d7c9eed171647e421013@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Cc: Edward Adam Davis <eadavis@qq.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 5e28b7b ("drm: Set old handle to NULL before prime swap in change_handle")
Cc: David Francis <David.Francis@amd.com>
Cc: Puttimet Thammasaeng <pwn8official@gmail.com>
Cc: Christian Koenig <Christian.Koenig@amd.com>
Fixes: 7164d78 ("drm/gem: fix race between change_handle and handle_delete")
Cc: Zhenghang Xiao <kipreyyy@gmail.com>

[Commit description truncated; see the upstream URL below]

Changed files:
  drivers/gpu/drm/drm_gem.c
  drivers/gpu/drm/drm_ioctl.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=c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd

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

The original Linux kernel CVE announcement for CVE-2026-53145 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53145

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: 7
  Paranoid ActionableScore: 8

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).