[CVE-2026-53355][MODERATE 7.0] net: rds: clear i_sends on setup unwind

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

CVE: CVE-2026-53355
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: rds: clear i_sends on setup unwind
Commit: 66cccec111421a10efdc2c74499d15b93e7acae5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=66cccec111421a10efdc2c74499d15b93e7acae5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53355
Analysis date: Wed, 01 Jul 2026 10:32:34 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-53355 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53355

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-2026-53355	MODERATE	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-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A stale pointer bug exists in the RDS IB connection setup unwind path. If rds_ib_setup_qp() fails after allocating i_sends but before allocating i_recvs, the error path frees i_sends but leaves the pointer non NULL. A later teardown or repeated shutdown pass can treat the stale pointer as an owned live send ring and may trigger a double-free or use-after-free condition. For the CVSS the PR:L is used because practical triggering normally requires a local user or process that can initiate RDS IB connection setup on the affected host. The attack complexity is high because the bug depends on a partial setup failure and a later cleanup pass. Impact is at least local denial of service via kernel crash. In the paranoid score, confidentiality and integrity are raised because the patch context indicates a stale freed kernel pointer and a plausible memory corruption class that should not be autoclosed without manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-53355  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX LINUS  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4

1. ActionableScore
* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

2. Signal breakdown
* Local unprivileged trigger: +1. RDS sockets and connection setup may be reachable by a local user if RDS IB is enabled and configured.
* Memory corruption, strong lifetime primitive: +2. The patch fixes a stale pointer after vfree(), which can allow later teardown to treat freed i_sends memory as still owned.
* Real lifetime corruption: +1. This is a resource ownership and lifetime bug involving stale pointer reuse after free.
* Reliable kernel crash / strong DoS: +1. A later shutdown path can plausibly cause double-free, UAF, or allocator failure leading to kernel crash.
* Hard or unreliable trigger condition: -1. Triggering requires rds_ib_setup_qp() to fail in a narrow partial initialization window after i_sends allocation but before i_recvs allocation.
* Rare and difficult-to-reach subsystem/configuration: -1. RDS over InfiniBand is not a default common Internet-facing path and needs RDMA/RDS configuration.
* Paranoid weak LPE concern: +1. A stale freed kernel pointer creates a plausible memory corruption class, but no attacker-controlled reclaim, overwrite, callback dispatch, or type confusion is demonstrated.

3. Reachability analysis
The realistic trigger is local and configuration-dependent. An attacker likely needs local code execution on a system where RDS IB is loaded, configured, and usable. This is not realistically Internet remote. Network activity over an RDMA fabric may influence connection setup, but the key failure condition depends on local setup unwind and later teardown behavior. Namespaces or container delegation could reduce the effective privilege requirement if untrusted workloads can access RDS sockets or RDMA resources, so PR:L is the safer triage assumption.

4. Severity interpretation
This is more than an ordinary Moderate resource cleanup bug because the freed pointer remains stored and can be consumed by later teardown logic. The demonstrated impact is most clearly DoS through double-free or UAF-triggered crash. Theoretical privilege escalation is not proven, because the patch does not show controlled reclaim, controlled write, function pointer corruption, or object replacement. However, the lifetime corruption pattern is strong enough to avoid auto-close and warrants manual review.

5. One-sentence report phrase
A stale pointer in the RDS IB setup unwind path can leave freed i_sends memory marked as owned, allowing later teardown to trigger a double-free or use-after-free condition and causing at least local DoS, with weak but review-worthy LPE concern.

6. Manual review recommendation
MANUAL CHECK REQUIRED.
Reason: this is a real stale-pointer-after-free lifetime bug in kernel networking/RDMA code, with plausible double-free or UAF behavior even though practical privilege escalation is not demonstrated.

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

Patch: net: rds: clear i_sends on setup unwind
Commit: 66cccec111421a10efdc2c74499d15b93e7acae5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=66cccec111421a10efdc2c74499d15b93e7acae5

Commit description:

The RDS IB connection teardown path is written so it can run during
partial startup and on repeated shutdown attempts. It uses NULL
pointers to distinguish resources that are still owned from resources
that have already been released.

When rds_ib_setup_qp() fails after allocating i_sends but before
allocating i_recvs, the sends_out path frees i_sends without clearing
the pointer. A later shutdown pass can still treat that stale pointer
as a live send ring allocation.

Clear i_sends after vfree() in the error unwind path so the existing
shutdown logic continues to use the correct ownership state.

Fixes: 3b12f73 ("rds: ib: add error handle")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Zhengchuan Liang <zcliangcn@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Yuqi Xu <xuyq21@lenovo.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Reviewed-by: Allison Henderson <achender@kernel.org>
Link: https://patch.msgid.link/5a0f7624bb9845a7b67d26166a150b59e7f394ce.1779632468.git.xuyq21@lenovo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/rds/ib_cm.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=66cccec111421a10efdc2c74499d15b93e7acae5

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

The original Linux kernel CVE announcement for CVE-2026-53355 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53355

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: 4
  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: 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).