[CVE-2026-46294][MODERATE 7.0] dm: fix a buffer overflow in ioctl processing

[CVE-2026-46294][MODERATE 7.0] dm: fix a buffer overflow in ioctl processing

[AL-KERNEL]

CVE: CVE-2026-46294
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: dm: fix a buffer overflow in ioctl processing
Commit: c8c5311237448f6ffeecc9aec2362e3692623668
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c8c5311237448f6ffeecc9aec2362e3692623668
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46294
Analysis date: Mon, 08 Jun 2026 15:16:45 -0400
ActionableScore: 7
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-46294 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46294

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
======================================================================

CVE-2026-46294	MODERATE	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-787;CWE-190;CWE-119;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A kernel buffer overflow in dm ioctl retrieve_status can occur because outptr is aligned after writing status data without verifying that the aligned pointer still remains inside the ioctl output buffer. If the aligned pointer moves past the end, the later remaining length calculation can wrap and allow additional status data to be written out of bounds. For the CVSS the PR:L reflects a paranoid but still defensible deployment model where device mapper control is delegated to a storage service, reduced capability root, or container like administrative context rather than full trusted host root. The issue is not network reachable and requires local access to the device mapper control interface. Impact is at least local denial of service and in the worst case may allow confidentiality or integrity impact due to kernel heap memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) 	MAYBE	OOB DISK HARDWARE LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	-	-	checked

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

ActionableScore=7
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

2. Signal breakdown
* Generic memory corruption: +2. The bug can write past the end of the kernel ioctl buffer after `align_ptr(outptr)` moves the pointer beyond `outbuf + len` and the remaining length calculation wraps.
* Privilege escalation plausible: +2 in paranoid scoring. This is a kernel heap overflow class bug, so LPE is technically plausible, although not demonstrated and likely constrained.
* Reliable kernel crash / strong DoS: +1. Out of bounds kernel writes can realistically crash the kernel.
* Privileged kernel/device-management memory corruption path: +1. The affected path is device mapper ioctl processing in a highly trusted storage management subsystem.
* Important filesystem/storage path: +1. Device mapper is a core block/storage component, although this is a control-plane ioctl rather than normal IO.
* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2 for the conservative score. Device mapper ioctls are normally root or CAP_SYS_ADMIN controlled.
* Special triggering conditions: -1 for the conservative score. Common libraries use 8-byte aligned buffer sizes, so accidental triggering is unlikely.
* Constrained primitive caveat. Payload and target control are not clearly strong from the patch alone, so the conservative score treats this as manual-review memory corruption rather than proven exploitable LPE.

3. Reachability analysis
The normal trigger requires local access to the device mapper control ioctl, typically available only to root or a process with equivalent storage administration privileges. In conservative deployments this is a root-only bug and may have limited practical security impact beyond crashing a system already controlled by root. In paranoid deployments, device mapper access may be delegated to storage management daemons, reduced-capability root, container-like admin contexts, or service accounts, so PR:L-style handling is defensible for triage. The path is not network reachable by itself. Realistic exploitation requires a specially sized non-8-byte-aligned ioctl buffer and status output that causes the loop to continue after alignment overshoots the buffer.

4. Severity interpretation
This is not an ordinary resource leak or warning-only bug. It is a kernel out-of-bounds write caused by unchecked pointer alignment and unsigned length wraparound. The realistic impact may be limited because the interface is normally privileged and common userspace libraries avoid the bad buffer shape. However, because the primitive is kernel memory corruption in a storage control path, it should not be auto-closed as low-risk solely based on the maintainer note that only root normally issues these ioctls. The conservative view is borderline manual review. The paranoid view is a Strong Important candidate if delegated device-mapper access exists or if further analysis shows useful heap corruption control.

5. One-sentence report phrase
A device mapper ioctl buffer overflow in `retrieve_status()` can occur when aligned output pointer accounting moves past the supplied buffer and wraps the remaining length, allowing kernel out-of-bounds writes from a local device-mapper control context.

6. Manual review recommendation
MANUAL CHECK REQUIRED.
Reason: this is a kernel heap out-of-bounds write in a privileged storage ioctl path, and the practical severity depends heavily on whether device mapper control is strictly host-root-only or delegated to less trusted local service or container contexts.

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

Patch: dm: fix a buffer overflow in ioctl processing
Commit: c8c5311237448f6ffeecc9aec2362e3692623668
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c8c5311237448f6ffeecc9aec2362e3692623668

Commit description:

Tony Asleson (using Claude) found a buffer overflow in dm-ioctl in the
function retrieve_status:

1. The code in retrieve_status checks that the output string fits into
   the output buffer and writes the output string there
2. Then, the code aligns the "outptr" variable to the next 8-byte
   boundary:
	outptr = align_ptr(outptr);
3. The alignment doesn't check overflow, so outptr could point past the
   buffer end
4. The "for" loop is iterated again, it executes:
	remaining = len - (outptr - outbuf);
5. If "outptr" points past "outbuf + len", the arithmetics wraps around
   and the variable "remaining" contains unusually high number
6. With "remaining" being high, the code writes more data past the end of
   the buffer

Luckily, this bug has no security implications because:
1. Only root can issue device mapper ioctls
2. The commonly used libraries that communicate with device mapper
   (libdevmapper and devicemapper-rs) use buffer size that is aligned to
   8 bytes - thus, "outptr = align_ptr(outptr)" can't overshoot the input
   buffer and the bug can't happen accidentally

Reported-by: Tony Asleson <tasleson@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Bryn M. Reeves <bmr@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/md/dm-ioctl.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=c8c5311237448f6ffeecc9aec2362e3692623668

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

The original Linux kernel CVE announcement for CVE-2026-46294 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46294

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:H/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: 3
  Paranoid ActionableScore: 7

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).