[CVE-2026-53333][LOW] mm/mincore: handle non-swap entries before !CONFIG_SWAP guard

[CVE-2026-53333][LOW] mm/mincore: handle non-swap entries before !CONFIG_SWAP guard

[AL-KERNEL]

CVE: CVE-2026-53333
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: mm/mincore: handle non-swap entries before !CONFIG_SWAP guard
Commit: a8f91ddf67f669f547bb9fb559738da6f8ee2cf3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a8f91ddf67f669f547bb9fb559738da6f8ee2cf3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53333
Analysis date: Wed, 01 Jul 2026 10:04:46 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
`mincore() on !CONFIG_SWAP kernels can mishandle migration, hwpoison, or shmem swapin-error entries, causing a spurious WARN and incorrect page residency reporting, with local DoS impact mainly on systems where WARN is fatal.`

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

The original Linux kernel CVE announcement for CVE-2026-53333 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53333

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: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-53333	LOW	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:N/I:N/A:H';CWE-617;CWE-754;CWE-682;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'mincore on a kernel built without CONFIG_SWAP can spuriously hit a WARN path and report pages as nonresident because non-swap entries such as migration, hwpoison, or shmem swapin-error entries are checked too late. This is a local logic and error handling issue rather than a memory corruption primitive. For the CVSS the PR:L is used because a local user can call mincore on mappings in its own process, but reliable triggering also depends on kernel build options and special PTE states. The issue is not network reachable. Impact is mainly incorrect residency reporting and local denial of service if WARN is treated as fatal. For the paranoid score, A:H is still defensible only on systems where WARN can panic the kernel, while C and I remain N because the patch does not show an information leak or write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-53333  SKIP The Fixes patch not applied yet, so unlikely that actual: 1f2052755c152940c336918bd73d13d5468f548b YES  NO NO unknown 	MAYBE	SIMPLEFIX HARDWARE LINUS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. `mincore()` is a local userspace syscall and can be called by an unprivileged process on its own mappings.
* Rare AND difficult-to-reach subsystem/configuration: -1. The issue requires a kernel built without `CONFIG_SWAP`, while still having migration, hwpoison, or shmem swapin-error entries.
* WARN_ON continuation / correctness concern: +1. The bug can spuriously hit `WARN_ON(1)` and return an incorrect residency result, but the patch does not show memory corruption, UAF, OOB access, arbitrary write, or information disclosure.

Paranoid additions:

* Availability impact under panic-on-warn style deployments: +1. If `panic_on_warn` or similar policy is enabled, the WARN path can become a local DoS. This is not the default impact for all systems.

Not counted:

* No remote reachability.
* No generic memory corruption.
* No real lifetime corruption.
* No privilege escalation primitive.
* No confidentiality or integrity impact.
* No Dirty-Pipe-like or page-cache ownership bypass primitive.

## 3. Reachability analysis

A local user can call `mincore()`, so PR is effectively local unprivileged for reachability. Reliable triggering is not generic because it depends on a `!CONFIG_SWAP` kernel and special non-swap PTE states such as migration, hwpoison, or shmem swapin-error entries. Containers do not materially improve exploitability unless they can create the required memory state, and this is not a network-triggerable path. The affected path is core mm code, but the vulnerable condition is configuration and state dependent.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like correctness and local DoS issue. The demonstrated effect is a spurious WARN and incorrect `mincore()` residency reporting. Theoretical DoS becomes stronger only on systems where WARN is fatal. There is no evidence in the patch of UAF, stale pointer reuse, OOB write, object confusion, refcount abuse, information leak, or privilege escalation.

## 5. One-sentence report phrase

`mincore() on !CONFIG_SWAP kernels can mishandle migration, hwpoison, or shmem swapin-error entries, causing a spurious WARN and incorrect page residency reporting, with local DoS impact mainly on systems where WARN is fatal.`

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a local correctness/WARN issue with no concrete memory corruption or security-boundary bypass primitive. It can be handled as low-priority unless the affected product treats user-triggerable WARN paths as mandatory review.

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

Patch: mm/mincore: handle non-swap entries before !CONFIG_SWAP guard
Commit: a8f91ddf67f669f547bb9fb559738da6f8ee2cf3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a8f91ddf67f669f547bb9fb559738da6f8ee2cf3

Commit description:

mincore_swap() also fields migration/hwpoison entries (and shmem
swapin-error entries), which can exist on !CONFIG_SWAP builds when
CONFIG_MIGRATION or CONFIG_MEMORY_FAILURE is enabled.  The
!IS_ENABLED(CONFIG_SWAP) guard ran before the non-swap-entry early return,
so mincore_pte_range() can spuriously WARN and report these pages
nonresident on !CONFIG_SWAP kernels.

Move the guard below the non-swap-entry check so only true swap entries
trip the WARN, and migration/hwpoison entries take the existing "uptodate
/ non-shmem" path.

Link: https://lore.kernel.org/20260602172247.279421-1-usama.arif@linux.dev
Fixes: 1f20527 ("mm/mincore: use a helper for checking the swap cache")
Signed-off-by: Usama Arif <usama.arif@linux.dev>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  mm/mincore.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=a8f91ddf67f669f547bb9fb559738da6f8ee2cf3

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

The original Linux kernel CVE announcement for CVE-2026-53333 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53333

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).