[CVE-2026-74584][MODERATE REGULAR] RDMA/bnxt_re: zero shared page before exposing to userspace

[CVE-2026-74584][MODERATE REGULAR] RDMA/bnxt_re: zero shared page before exposing to userspace

[AL-KERNEL]

CVE: CVE-2026-74584
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: RDMA/bnxt_re: zero shared page before exposing to userspace
Commit: 53c97e9882f4e747b4ac31b211317c2eba541af9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=53c97e9882f4e747b4ac31b211317c2eba541af9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74584
Analysis date: Sat, 22 Aug 2026 10:51:56 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended due to direct kernel memory disclosure
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74584 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74584

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 REGULAR
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-2026-74584	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N';*CWE-200;CWE-226;CWE-908;BEST CVSS score: '5.5';DESCR 'An information disclosure exists in the bnxt_re RDMA driver because bnxt_re_alloc_ucontext() allocates uctx shpg with __get_free_page() and the page is not zeroed before it can be mapped to userspace. A local user with access to /dev/infiniband/uverbsX on a host with a bnxt_re device can obtain the shared page through the uverbs context and mmap path, while only a small u32 field is initialized and the remaining page bytes may contain stale kernel memory. For the CVSS the PR:L is used because the attacker needs local access to the RDMA userspace verbs device, typically through rdma group membership or an equivalent device access policy. The issue is not directly network reachable and does not require packet traffic to trigger. Impact is confidentiality loss from kernel memory disclosure, with no direct integrity or availability impact from this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended due to direct kernel memory disclosure (with actual score 4)	YES	READ INIT LEAK UAF NETWORK HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	guess

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

ActionableScore=4

1. ActionableScore
* Conservative score: 4
* Paranoid score: 4
* Final recommended bucket: **Borderline / manual review recommended due to direct kernel memory disclosure**::

2. Signal breakdown
* Local unprivileged or low privileged trigger: +1. A local user with access to `/dev/infiniband/uverbsX`, typically via RDMA device permissions or `rdma` group membership, can reach the mmap path.
* Security-boundary bypass with practical sensitive-object access: +2. An unzeroed kernel page is mapped into userspace, directly crossing the kernel to userspace confidentiality boundary.
* Confidentiality impact plausible: +1. The leaked 4092 bytes may contain stale kernel heap or page allocator contents, including pointers or sensitive fragments.
* No generic memory corruption: +0. The patch shows an information leak only, not UAF, OOB write, arbitrary write, refcount misuse, or type confusion.
* No integrity or availability signal: +0. No write primitive or crash path is indicated.
* No RDMA high-control API bonus: +0. The RDMA uverbs path exposes the page, but the patch does not show attacker control over object lifetime, callback targets, DMA mappings, refcounts, or allocator layout beyond reading the stale page.

3. Reachability analysis
The trigger is local and requires access to a bnxt_re RDMA userspace verbs device. This is not network reachable by packet traffic alone. In typical deployments, `/dev/infiniband/uverbsX` access is restricted by device permissions, group membership, containers, or RDMA policy, so this is best treated as PR:L rather than PR:N. The affected path is hardware and configuration dependent because it requires a Broadcom bnxt_re RoCE device and exposed uverbs access, but once those conditions exist the trigger is simple: create an RDMA userspace context and mmap the shared page.

4. Severity interpretation
This behaves like an actionable information disclosure, not an Important memory corruption issue. The primitive is concrete and directly supported by the patch: an uninitialized kernel page allocated by `__get_free_page()` is exposed to userspace through `vm_insert_page()`. Realistic impact is kernel memory disclosure that may assist KASLR bypass or leak sensitive stale data, but there is no evidence of privilege escalation, arbitrary write, UAF, or DoS. Because it is direct kernel memory exposure, it should not be auto-closed as a trivial cleanup.

5. One-sentence report phrase
A local user with access to a bnxt_re RDMA uverbs device can mmap an unzeroed shared page and read stale kernel memory, causing a confidentiality impact without direct integrity or availability impact.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Direct kernel memory disclosure to userspace is a security-relevant primitive even without memory corruption or LPE evidence, and affected product exposure depends on RDMA device permissions and bnxt_re deployment.

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

Patch: RDMA/bnxt_re: zero shared page before exposing to userspace
Commit: 53c97e9882f4e747b4ac31b211317c2eba541af9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=53c97e9882f4e747b4ac31b211317c2eba541af9

Commit description:

bnxt_re_alloc_ucontext() allocates uctx->shpg via
__get_free_page(GFP_KERNEL). The buddy allocator does not zero pages
without __GFP_ZERO, so the page contains stale kernel data from
whatever object most recently freed it.

The page is then mapped into userspace via vm_insert_page() under
BNXT_RE_MMAP_SH_PAGE in bnxt_re_mmap(). The driver only ever writes
4 bytes (a u32 AVID) at offset BNXT_RE_AVID_OFFT (0x10) inside
bnxt_re_create_ah(); the remaining 4092 bytes of the page are exposed
to userspace unsanitised, leaking kernel memory contents.

Any user with access to /dev/infiniband/uverbsX on a host with a
bnxt_re device (typically rdma group membership) can read this data
via a single mmap() at pgoff 0 after IB_USER_VERBS_CMD_GET_CONTEXT.

Other shared pages in the same file already use get_zeroed_page()
correctly:

  drivers/infiniband/hw/bnxt_re/ib_verbs.c
      srq->uctx_srq_page = (void *)get_zeroed_page(GFP_KERNEL);
      cq->uctx_cq_page  = (void *)get_zeroed_page(GFP_KERNEL);

uctx->shpg is the only outlier. Bring it in line with the existing
convention by switching to get_zeroed_page().

Fixes: 1ac5a40 ("RDMA/bnxt_re: Add bnxt_re RoCE driver")
Signed-off-by: Lord Ulf Henrik Holmberg <henrik.holmberg@defensify.se>
Link: https://patch.msgid.link/20260509084011.11971-1-pomzm67@gmail.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/infiniband/hw/bnxt_re/ib_verbs.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=53c97e9882f4e747b4ac31b211317c2eba541af9

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

The original Linux kernel CVE announcement for CVE-2026-74584 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74584

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
  The Best / paranoid CVSS score: 5.5

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: unknown
  Paranoid ActionableScore: 4

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 REGULAR

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).