[CVE-2026-46176][IMPORTANT] RDMA/mlx5: Fix error path fall-through in mlx5_ib_dev_res_srq_init()

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

CVE: CVE-2026-46176
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: RDMA/mlx5: Fix error path fall-through in mlx5_ib_dev_res_srq_init()
Commit: a13c2ac4d480b734342c6fbf8249fc48afd675f3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a13c2ac4d480b734342c6fbf8249fc48afd675f3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46176
Analysis date: Thu, 28 May 2026 10:49:39 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
`mlx5_ib_dev_res_srq_init()` can fall through after partial SRQ initialization failure, storing a freed SRQ pointer and an `ERR_PTR` in device state and causing later UAF, `ERR_PTR` dereference, or double free.

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

The original Linux kernel CVE announcement for CVE-2026-46176 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46176

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-2026-46176	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-416;CWE-415;**CWE-476;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'mlx5_ib_dev_res_srq_init can fall through after s1 SRQ allocation fails, storing a freed s0 pointer and an ERR_PTR s1 into the device resource state. Later fast paths can treat the resources as initialized and dereference the freed SRQ or ERR_PTR, while cleanup can double free s0. For the CVSS the PR:L is used because a local user with RDMA uverbs or delegated mlx5 device access may trigger resource initialization, although reliable triggering depends on forcing the s1 failure path after s0 succeeds. The issue is not network reachable by itself. Impact is at least local denial of service via kernel crash, and worst case may allow confidentiality or integrity impact because the bug creates kernel use-after-free and double-free conditions.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) 	MAYBE	DANGER ERRORPATH UAF NETWORK KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user with RDMA/uverbs or delegated mlx5 device access may trigger first-use resource initialization.
* Generic memory corruption: +2. The error path can store a freed SRQ pointer and later double free it.
* Real lifetime corruption: +1. `s0` is destroyed but then saved in device resource state.
* Reliable kernel crash / strong DoS: +1. Later dereference of freed `s0`, dereference of `ERR_PTR s1`, or cleanup double free can crash the kernel.
* Local high-control device API: +1. RDMA resource creation exposes user-driven object lifecycle and allocation paths.
* Hard failure condition: -1. Reliable triggering depends on `s1` allocation failure after `s0` succeeds.
* Constrained primitive: -1. The patch does not show controlled reclaim, overwrite target, or arbitrary write.

Paranoid additional signals:

* Weak to strong LPE concern: +1. UAF plus double free in kernel object state can be exploitable if allocation failure and object reuse are controllable.
* Privileged device-management memory corruption path: +1. The corrupted state is in trusted mlx5 RDMA device resource initialization.

## 3. Reachability analysis

The bug is local and depends on access to mlx5 RDMA functionality. A user with uverbs access can cause resource initialization paths to run, but exploitation requires a specific allocation failure: `s1` must fail after `s0` was successfully created.

No direct network trigger is shown. Containers matter if RDMA devices are delegated into a container or to untrusted workloads. The affected mlx5 RDMA path is common in RDMA-enabled servers, but the failure condition makes reliable exploitation harder than normal ioctl misuse.

## 4. Severity interpretation

This is a Strong Important candidate under paranoid triage and at least actionable Moderate. The realistic impact is local DoS via kernel crash during later resource use or cleanup.

The higher concern is possible privilege escalation because the bug creates persistent corrupted kernel state containing a freed pointer and an `ERR_PTR`. No concrete LPE chain is shown, so this should be treated as manual-review required rather than proven Important.

## 5. One-sentence report phrase

`mlx5_ib_dev_res_srq_init()` can fall through after partial SRQ initialization failure, storing a freed SRQ pointer and an `ERR_PTR` in device state and causing later UAF, `ERR_PTR` dereference, or double free.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is kernel lifetime corruption in an RDMA/mlx5 resource path, and practical severity depends on RDMA device exposure and whether untrusted users can reliably induce the partial allocation failure.

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

Patch: RDMA/mlx5: Fix error path fall-through in mlx5_ib_dev_res_srq_init()
Commit: a13c2ac4d480b734342c6fbf8249fc48afd675f3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a13c2ac4d480b734342c6fbf8249fc48afd675f3

Commit description:

mlx5_ib_dev_res_srq_init() allocates two SRQs, s0 and s1. When
ib_create_srq() fails for s1, the error branch destroys s0 but falls
through and unconditionally assigns the freed s0 and the ERR_PTR s1 to
devr->s0 and devr->s1.

This leads to several problems: the lock-free fast path checks
"if (devr->s1) return 0;" and treats the ERR_PTR as already initialised;
users in mlx5_ib_create_qp() dereference the freed SRQ or ERR_PTR via
to_msrq(devr->s0)->msrq.srqn; and mlx5_ib_dev_res_cleanup() dereferences
the ERR_PTR and double-frees s0 on teardown.

Fix by adding the same `goto unlock` in the s1 failure path.

Cc: stable@vger.kernel.org
Fixes: 5895e70 ("IB/mlx5: Allocate resources just before first QP/SRQ is created")
Link: https://patch.msgid.link/r/SYBPR01MB7881E1E0970268BD69C0BA75AF2B2@SYBPR01MB7881.ausprd01.prod.outlook.com
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/infiniband/hw/mlx5/main.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=a13c2ac4d480b734342c6fbf8249fc48afd675f3

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

The original Linux kernel CVE announcement for CVE-2026-46176 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46176

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: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: 6
  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).