[CVE-2026-64153][LOW] drm/msm: Fix iommu_map_sgtable() return value check and avoid WARN [ Upstream

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

CVE: CVE-2026-64153
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/msm: Fix iommu_map_sgtable() return value check and avoid WARN [ Upstream
Commit: 3c2cdb7c07f664b77e2a75b50793b845d5742efa
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3c2cdb7c07f664b77e2a75b50793b845d5742efa
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64153
Analysis date: Sun, 19 Jul 2026 15:17:35 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
The drm/msm IOMMU mapping path stored a negative `iommu_map_sgtable()` error in an unsigned variable, causing incorrect error handling, but the visible impact is limited to local GPU mapping failure behavior without demonstrated memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-64153 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64153

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.

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

CVE-2026-64153	LOW	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:N/I:N/A:L';CWE-681;CWE-704;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:N';BEST CVSS score: '2.5';DESCR 'The drm/msm IOMMU mapping path used an unsigned size_t variable for the return value of iommu_map_sgtable even though the API can return negative error codes. A negative error can be converted into a large positive value and the original failure reason is lost, causing incorrect error handling in the GPU mapping path. For the CVSS the PR:L is used in the conservative scoring because triggering would require a local process that can exercise the drm/msm GPU or DRM mapping interface. The issue is not network reachable. Impact appears limited to failed GPU mapping operations or limited local availability impact in error paths, with no evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-64153 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WARNONLY SIMPLEFIX HARDWARE LINUS 	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* `+0 WARN_ON continuation / error handling concern`
  The patch fixes incorrect handling of a negative `iommu_map_sgtable()` return value and avoids WARN-style behavior. The patch does not show a later Oops, UAF, OOB access, double free, stale pointer use, or corruption sink.

* `+0 no demonstrated memory corruption`
  The signedness bug can convert a negative error into a large unsigned value, but the shown caller still returns failure when `ret != len`. There is no evidence that the large value is used as a copy length, allocation size, array index, DMA length, or object selector.

* `+0 no demonstrated confidentiality or integrity impact`
  The failure path appears to lose the original error code and return `-EINVAL`, not expose data or modify protected state.

* `-1 rare / hardware-specific path`
  The affected code is specific to the Qualcomm MSM DRM GPU IOMMU mapping path and requires an IOMMU mapping error condition.

* `+1 local unprivileged trigger, paranoid only`
  In some deployments DRM render nodes may be usable by local unprivileged users, so a local process might be able to exercise GPU mapping paths. This is not enough to make the issue actionable because the impact remains limited.

No points awarded for:

* remote reachability
* privilege escalation
* generic memory corruption
* real lifetime corruption
* reliable kernel crash
* Dirty-Pipe-like primitive
* high-control API bonus
* security-boundary bypass

## 3. Reachability analysis

The affected path is local and device-specific. A practical trigger would require a process that can use the `drm/msm` GPU interface and can cause `iommu_map_sgtable()` to fail. On many systems DRM render nodes may be exposed to local users, but this still requires local code execution and suitable MSM GPU hardware. Containers or namespaces do not automatically make this more severe unless the DRM device is explicitly passed through. There is no realistic network trigger.

Call-site confidence: high, because the changed function and immediate return-value use are visible in the patch.

## 4. Severity interpretation

This behaves like a low-risk correctness and error-propagation issue, not an Important-class vulnerability. The theoretical concern is signedness-related error confusion, but the visible code does not convert that confusion into memory corruption, information disclosure, privilege escalation, or a reliable system-wide DoS. The realistic impact is failed GPU mapping behavior or less precise error reporting.

## 5. One-sentence report phrase

The drm/msm IOMMU mapping path stored a negative `iommu_map_sgtable()` error in an unsigned variable, causing incorrect error handling, but the visible impact is limited to local GPU mapping failure behavior without demonstrated memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: no concrete corruption primitive, no remote exposure, no security-boundary bypass, and no reliable crash path is demonstrated by the patch.

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

Patch: drm/msm: Fix iommu_map_sgtable() return value check and avoid WARN [ Upstream
Commit: 3c2cdb7c07f664b77e2a75b50793b845d5742efa
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3c2cdb7c07f664b77e2a75b50793b845d5742efa

Changed files:
  drivers/gpu/drm/msm/msm_iommu.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=3c2cdb7c07f664b77e2a75b50793b845d5742efa

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

The original Linux kernel CVE announcement for CVE-2026-64153 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64153

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:N/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 2.5

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: 0
  Paranoid ActionableScore: 1

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).