[CVE-2026-80835][MODERATE 7.0] crypto: qcom-rng - Remove crypto_rng interface

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

CVE: CVE-2026-80835
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: crypto: qcom-rng - Remove crypto_rng interface
Commit: bb474dcd9d0224264a27a60891f00872b879835f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bb474dcd9d0224264a27a60891f00872b879835f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80835
Analysis date: Fri, 04 Sep 2026 17:02:49 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
The qcom-rng driver exposed the same hardware RNG through both crypto_rng and hwrng without shared synchronization, allowing concurrent register access that may produce repeated or non-random output and weaken cryptographic material on affected Qualcomm platforms.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80835 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80835

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-2026-80835	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80835 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:H/I:H/A:N';CWE-362;CWE-330;CWE-338;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N';BEST CVSS score: '6.3';DESCR 'The qcom rng driver exposed the same hardware RNG through both crypto_rng and hwrng interfaces without common synchronization for accesses to the shared hardware registers. Concurrent generation through qcom_rng_generate() and qcom_hwrng_read() can cause repeated output or non random values, which may weaken cryptographic material that depends on this RNG. For the CVSS the PR:L is used because a local user or local process is needed to trigger the crypto_rng side through AF_ALG while hwrng activity is present. The issue is not directly network reachable. Impact is not a kernel crash but possible confidentiality and integrity degradation through weakened randomness. The base score uses low C and I impact, while the paranoid score treats RNG output degradation as potentially high impact in deployments where the affected RNG contributes to keys, nonces, or tokens.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	LOCK INIT ERRORPATH HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. The removed crypto_rng interface was reachable through AF_ALG rng operations when enabled.
* Local unprivileged high-control kernel data-plane API refinement: +1. AF_ALG lets a local process issue controlled RNG generation requests and shape timing against hwrng activity.
* Confidentiality impact plausible: +1. Repeated or non-random RNG output can weaken keys, nonces, session material, or tokens generated from affected entropy paths.
* Integrity impact plausible: +1. Weak randomness can undermine cryptographic integrity assumptions for signatures, authentication tokens, or protocol nonces.
* Hard or unreliable race / special timing required: -1. The issue depends on concurrent access through crypto_rng and hwrng to the same hardware registers.
* Legacy / non-default execution mode: -1. The commit explicitly states that the crypto_rng AF_ALG rng algorithm type is not used in practice.

Paranoid additional interpretation:

* Broad/default/common subsystem or broadly deployed exposure: +1. On affected Qualcomm platforms, hwrng can be part of the system entropy source, so RNG quality problems may affect security-sensitive consumers.
* Practical exploit chain strongly implied: +1. The commit directly states potential repetition of output and output of non-random values, which is a concrete cryptographic failure mode rather than only a theoretical race.
* Paranoid score does not subtract the AF_ALG rarity as strongly, because an attacker can intentionally use the exposed crypto_rng interface if it is registered.

No memory-corruption signals are awarded. This is not UAF, OOB write, double free, type confusion, or arbitrary write.

## 3. Reachability analysis

The realistic trigger is local. A local process would need to use the crypto_rng side, likely through AF_ALG rng, while hwrng reads occur concurrently. No direct network reachability is supported by the patch. Namespaces do not obviously create a separate remote or container escape path, but local access to AF_ALG may make the crypto_rng side reachable without full root privileges depending on product configuration. The issue is hardware and configuration dependent because it requires the qcom-rng driver on affected Qualcomm SoCs and the removed crypto_rng registration path.

Call-site confidence: medium. The patch includes the removed crypto_rng implementation, the hwrng implementation, and the shared qcom_rng_read hardware access path, but not all possible consumers of AF_ALG rng or hwrng entropy.

## 4. Severity interpretation

This behaves more like an actionable cryptographic Moderate than an ordinary low-risk cleanup. The patch does not support privilege escalation or kernel memory corruption, so it should not be classified as Important solely on bug class. However, RNG output repetition or non-random output can have high downstream security impact when the affected RNG contributes to cryptographic material. Conservative handling is Borderline / manual review recommended. Paranoid handling is Actionable Moderate because cryptographic confidentiality and integrity can be affected even without crash or memory corruption.

## 5. One-sentence report phrase

The qcom-rng driver exposed the same hardware RNG through both crypto_rng and hwrng without shared synchronization, allowing concurrent register access that may produce repeated or non-random output and weaken cryptographic material on affected Qualcomm platforms.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED. YES REQUIRES MANUAL CHECK because this is not memory corruption, but RNG quality bugs can silently affect confidentiality and integrity depending on how the affected platform feeds entropy into keys, nonces, and tokens.

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

Patch: crypto: qcom-rng - Remove crypto_rng interface
Commit: bb474dcd9d0224264a27a60891f00872b879835f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bb474dcd9d0224264a27a60891f00872b879835f

Commit description:

qcom-rng.c exposes the same hardware through two completely separate
interfaces, crypto_rng and hwrng.  However, the implementation of this
is buggy because it permits generation operations from these interfaces
to run concurrently with each other, accessing the same registers.  That
is, qcom_rng_generate() synchronizes with itself but not with
qcom_hwrng_read().  This results in potential repetition of output from
the RNG, output of non-random values, etc.

Fortunately, there's actually no point in hardware RNG drivers
implementing the crypto_rng interface.  It's not actually used by
anything besides the "rng" algorithm type of AF_ALG, which in turn is
not actually used in practice.  Other crypto_rng hardware drivers are
likewise being phased out, leaving just the hwrng support.

Thus, remove it to simplify the code and avoid conflict (and confusion)
with the hwrng interface which is the one that actually matters.

Fixes: f29cd5b ("crypto: qcom-rng - Add hw_random interface support")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/crypto/qcom-rng.c
  crypto/internal/rng.h

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=bb474dcd9d0224264a27a60891f00872b879835f

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

The original Linux kernel CVE announcement for CVE-2026-80835 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80835

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:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
  The Best / paranoid CVSS score: 6.3

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: 3
  Paranoid ActionableScore: 5

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 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).