[CVE-2026-43494][IMPORTANT] net/rds: reset op_nents when zerocopy page pin fails When iov_iter_get_pages2() fails in rds_message_zcopy_from_user(), the pinned pages are released with put_page(), and rm->data.op_mmp_znotifier is cleared. But we fail to properly clear rm->data.op_nents. Later when rds_message_purge() is called from rds_sendmsg() the cleanup loop iterates over the incorrectly non zero number of op_nents and frees them again. Fix this by properly resetting op_nents when it should be in rds_message_zcopy_from_user(). Fixes: 0cebacc ("rds: zerocopy Tx support.") Signed-off-by: Allison Henderson <achender@kernel.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260505234336.2132721-1-achender@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

CVE: CVE-2026-43494
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: net/rds: reset op_nents when zerocopy page pin fails When iov_iter_get_pages2() fails in rds_message_zcopy_from_user(), the pinned pages are released with put_page(), and rm->data.op_mmp_znotifier is cleared. But we fail to properly clear rm->data.op_nents. Later when rds_message_purge() is called from rds_sendmsg() the cleanup loop iterates over the incorrectly non zero number of op_nents and frees them again. Fix this by properly resetting op_nents when it should be in rds_message_zcopy_from_user(). Fixes: 0cebacc ("rds: zerocopy Tx support.") Signed-off-by: Allison Henderson <achender@kernel.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260505234336.2132721-1-achender@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Commit: e174929793195e0cd6a4adb0cad731b39f9019b4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e174929793195e0cd6a4adb0cad731b39f9019b4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43494
Analysis date: Thu, 21 May 2026 10:52:15 -0400
ActionableScore: 8
ActionableScore lower bound: 7
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local RDS zerocopy send error path can release pinned pages twice after `iov_iter_get_pages2()` failure because `op_nents` is not reset, creating page refcount lifetime corruption with DoS and plausible privilege escalation risk.

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

The original Linux kernel CVE announcement for CVE-2026-43494 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43494

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.

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

CVE-2026-43494	IMPORTANT	CHECK	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:H/A:H';CWE-415;*CWE-416;CWE-911;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A local memory lifetime bug exists in the RDS zero copy send path when iov_iter_get_pages2() fails after pages were pinned. The error path releases the pinned pages but leaves rm data op_nents non zero, so later rds_message_purge() can release the same pages again. For the CVSS the PR:L is used because a local user or process may be able to reach the RDS sendmsg zero copy path when AF_RDS and the relevant configuration are available. The issue is not directly network reachable because the trigger is a local sendmsg operation rather than received packet processing. Impact is at least local denial of service and the page reference lifetime corruption creates a plausible use after free or privilege escalation concern that should not be autoclosed.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)  SKIP CVE-2026-43494  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX IMPROVEONLY  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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

ActionableScore=8
ActionableScoreLower=7

## 1. ActionableScore

* Conservative score: 7
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Local unprivileged trigger: +1
  A local process may trigger the RDS `sendmsg()` zerocopy path if AF_RDS and zerocopy support are available.

* Local unprivileged high-control kernel data-plane API: +1
  The attacker can shape user iovecs and failure conditions around `iov_iter_get_pages2()` in a kernel networking transmit path.

* Generic memory corruption, strong corruption primitive: +2
  The bug causes the same pinned pages to be released twice via repeated `put_page()`, which is a page refcount lifetime corruption pattern.

* Real lifetime corruption: +1
  This is a real reference lifetime bug: pages are unpinned, but `op_nents` remains non zero, causing later cleanup to operate on stale accounting.

* Reliable kernel crash / strong DoS: +1
  Double page release can plausibly cause refcount underflow, page lifetime corruption, kernel warnings, crashes, or memory-management instability.

* Privilege escalation plausible: +1 conservative / +2 paranoid
  Conservative view treats this as a weak to moderate LPE concern because page refcount corruption can become exploitable but no concrete reclaim primitive is shown. Paranoid view gives stronger weight because double `put_page()` on user-controlled pinned pages is historically a dangerous primitive.

* Confidentiality and integrity impact plausible: +1 paranoid combined interpretation
  If the page lifetime corruption becomes controllable, reused pages could theoretically affect data confidentiality or integrity. This is not proven by the patch, but it is defensible for manual-review sensitivity.

* Rare/configuration dependency: -1 conservative only
  RDS is not universally enabled or exposed on all systems, and triggering depends on AF_RDS plus zerocopy Tx availability. This does not eliminate risk where the module/interface is available.

## 3. Reachability analysis

The trigger is local, not remote packet processing. A local user or process can potentially reach it through AF_RDS `sendmsg()` with zerocopy if RDS support is enabled and accessible. Containers or namespaces may matter if AF_RDS sockets are available inside the namespace, but many deployments restrict or do not load RDS. Realistic exploitation requires inducing a partial page-pin failure after some pages were pinned, then reaching the later purge path. That is more plausible than a narrow timing race because it is an error-path cleanup bug, not a pure race.

## 4. Severity interpretation

This should be treated as a Strong Important candidate rather than ordinary Moderate. The realistic demonstrated impact is at least local DoS from double page release and page refcount corruption. The theoretical but credible higher impact is privilege escalation through page lifetime misuse after premature page release. The patch does not prove arbitrary write or a full exploit chain, so it is not Critical by itself, but double `put_page()` on user-influenced pinned pages is serious enough to avoid auto-closure.

## 5. One-sentence report phrase

A local RDS zerocopy send error path can release pinned pages twice after `iov_iter_get_pages2()` failure because `op_nents` is not reset, creating page refcount lifetime corruption with DoS and plausible privilege escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

This is a local page lifetime corruption and double-release bug in a networking zerocopy path. Even without a demonstrated exploit, the primitive is strong enough to require manual review.

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

Patch: net/rds: reset op_nents when zerocopy page pin fails When iov_iter_get_pages2() fails in rds_message_zcopy_from_user(), the pinned pages are released with put_page(), and rm->data.op_mmp_znotifier is cleared. But we fail to properly clear rm->data.op_nents. Later when rds_message_purge() is called from rds_sendmsg() the cleanup loop iterates over the incorrectly non zero number of op_nents and frees them again. Fix this by properly resetting op_nents when it should be in rds_message_zcopy_from_user(). Fixes: 0cebacc ("rds: zerocopy Tx support.") Signed-off-by: Allison Henderson <achender@kernel.org> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260505234336.2132721-1-achender@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Commit: e174929793195e0cd6a4adb0cad731b39f9019b4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e174929793195e0cd6a4adb0cad731b39f9019b4

Changed files:
  net/rds/message.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=e174929793195e0cd6a4adb0cad731b39f9019b4

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

The original Linux kernel CVE announcement for CVE-2026-43494 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43494

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:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 7
  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).