[CVE-2026-80880][MODERATE 7.0] IB/mlx5: Properly support implicit ODP rereg_mr [ Upstream

[CVE-2026-80880][MODERATE 7.0] IB/mlx5: Properly support implicit ODP rereg_mr [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80880
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: IB/mlx5: Properly support implicit ODP rereg_mr [ Upstream
Commit: cbc9982c8573fb9e35040063aa78c8ebe768a1ff
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cbc9982c8573fb9e35040063aa78c8ebe768a1ff
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80880
Analysis date: Fri, 04 Sep 2026 18:05:28 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
IB/mlx5 implicit ODP rereg_mr could change a parent memory region in place while child mkeys still depended on its protection domain and translation state, creating a racy RDMA object lifetime condition that is locally reachable through RDMA uverbs and may lead to DoS or, in worst case, memory access isolation impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80880 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80880

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-2026-80880	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80880 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-362;*CWE-416;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'RDMA/mlx5 implicit ODP rereg_mr can race with child mkeys because the parent memory region may be changed in place while child objects still depend on the parent protection domain and translation state. A local user with access to RDMA uverbs can request rereg_mr on an implicit ODP MR and may trigger stale or inconsistent kernel object access during concurrent ODP activity. For the CVSS the PR:L is used for the paranoid score because reliable triggering requires a local process able to use the RDMA device, but this is often available to non root users through uverbs permissions or RDMA service accounts. The issue is not directly network reachable because rereg_mr is a local control path operation. Impact is at least denial of service and in worst case may include confidentiality or integrity impact due to a plausible use-after-free or stale pointer race around kernel RDMA objects.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	SIMPLEFIX NETWORK KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process with RDMA uverbs access can call rereg_mr on an implicit ODP MR.
* Memory corruption, weak/indirect corruption candidate: +1. The patch indicates unsafe in-place modification of a parent MR while child mkeys still depend on it, but does not show controlled reclaim, arbitrary write, or callback control.
* Real lifetime corruption: +1. The commit explicitly mentions racy access involving implicit children and mr->pd, which is a kernel object lifetime and ownership concern.
* Privileged kernel/device-management memory corruption path: +1. The affected objects are RDMA mlx5 memory registration, mkeys, ODP, and protection domains.
* Hard or unreliable race / special timing required: -1. The security-relevant part depends on a race with child mkeys touching the parent MR state.
* Rare AND difficult-to-reach subsystem/configuration: -1. Requires mlx5 RDMA hardware, ODP support, and userspace RDMA access.

Paranoid additional interpretation:

* Weak LPE concern: +1. A stale or inconsistent protection-domain reference in RDMA memory registration is security-sensitive enough to require manual review, even though no concrete exploit primitive is shown.
* Confidentiality impact plausible: +1. RDMA MR and PD confusion could potentially affect memory access isolation.
* Integrity impact plausible: +1. Incorrect MR or PD association could theoretically affect access permissions or DMA-visible mappings.
* Availability impact realistic: +1. Racy MR state can plausibly lead to crashes or device state corruption.
* Same race and deployment penalties still apply: -2 total.

No remote/network-triggerable signal is awarded. No strong memory corruption +2 is awarded because the patch does not demonstrate controlled UAF reclaim, arbitrary write, type confusion, refcount takeover, or attacker-controlled object replacement.

## 3. Reachability analysis

The likely trigger is local userspace through RDMA uverbs on mlx5 hardware. Root is not necessarily required if the system grants non-root users access to RDMA devices, which is common in HPC, storage, and RDMA service deployments. Containers or service accounts with delegated RDMA device access may also reduce the practical privilege barrier, so PR:L is more appropriate than PR:H for paranoid triage.

The path is not directly network reachable. Remote RDMA traffic alone is not enough unless it is combined with a local process or service that performs the affected rereg_mr operation. The affected configuration is not universal because it depends on mlx5, implicit ODP, and child mkey behavior, but it is relevant in real datacenter RDMA environments.

Call-site confidence: medium. The patch shows the changed rereg_mr logic and the commit explains the parent MR and child mkey relationship, but the full child mkey access paths are not included in the supplied diff.

## 4. Severity interpretation

This is more than an ordinary Moderate correctness fix because it involves racy access to RDMA memory registration objects and protection-domain state. The realistic demonstrated impact is not enough to claim a strong LPE primitive, because the patch does not show controlled memory reuse, write-after-free, arbitrary write, or a concrete privilege escalation path.

Conservatively it is a borderline manual-review issue. Paranoid triage should treat it as Actionable Moderate at minimum because RDMA MR and PD lifetime bugs can cross memory-access isolation boundaries if the stale state is exploitable.

## 5. One-sentence report phrase

IB/mlx5 implicit ODP rereg_mr could change a parent memory region in place while child mkeys still depended on its protection domain and translation state, creating a racy RDMA object lifetime condition that is locally reachable through RDMA uverbs and may lead to DoS or, in worst case, memory access isolation impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug involves RDMA memory registration, implicit ODP child mkeys, and racy access to mr->pd. There is no proven strong exploit primitive in the patch, but the affected object class is security-sensitive enough that auto-closing would risk missing a real memory isolation or privilege-impact issue.

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

Patch: IB/mlx5: Properly support implicit ODP rereg_mr [ Upstream
Commit: cbc9982c8573fb9e35040063aa78c8ebe768a1ff
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cbc9982c8573fb9e35040063aa78c8ebe768a1ff

Changed files:
  drivers/infiniband/hw/mlx5/mr.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=cbc9982c8573fb9e35040063aa78c8ebe768a1ff

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

The original Linux kernel CVE announcement for CVE-2026-80880 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80880

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: 6

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: YES
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).