* [CVE-2026-97585][MODERATE REGULAR] afs: Fix double-unmap of directory block
@ 2026-09-25 17:36 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 17:36 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97585
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: afs: Fix double-unmap of directory block
Commit: 9d6c703e24da3d39067e3c75f4ac2f6001c2472f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9d6c703e24da3d39067e3c75f4ac2f6001c2472f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97585
Analysis date: Fri, 25 Sep 2026 13:36:27 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97585 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97585
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 REGULAR
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-2026-97585 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97585 CHECK WITH IMPACT FROM ORIG NN NONE 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-675;*CWE-672;*CWE-664;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'AFS directory entry removal can perform kunmap_local twice for the same directory block because manual cleanup leaves iter.block pointing to an already unmapped block. A second afs_dir_find_block call, which occurs when the modified entry is not first in its hash chain, attempts to unmap the stale pointer again. This can unbalance local mapping state and may cause a warning, invalid mapping use, or a kernel crash. On configurations that use real temporary high memory mappings, corruption of the mapping stack may create a broader memory safety risk, although the available code does not establish a reliable arbitrary read or write primitive. For the CVSS the PR:L is selected because a local user with permission to modify the affected mounted AFS directory may reach the removal path without administrative privileges. The issue is not directly network reachable, although directory data supplied through an AFS deployment can influence the required hash chain layout. Impact is at least a local denial of service via kernel failure and in the paranoid case may include confidentiality or integrity impact due to incorrect page mapping state.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) SKIP CVE-2026-97585 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE DISK SIMPLEFIX SKIP LINUS INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 4
* Paranoid score: 4
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 Real lifetime violation. The first `kunmap_local(block)` ends the temporary mapping lifetime, but `iter.block` retains the stale address and a later `afs_dir_find_block()` performs another `kunmap_local()` on it.
* +1 Local unprivileged trigger. A user with write permission on an already mounted AFS directory can invoke directory-entry removal without host-admin privilege.
* Paranoid +1 Reliable kernel crash or strong DoS. On architectures using actual temporary high-memory mappings, the second unmap can unbalance local mapping-stack or migration state and plausibly cause a warning, invalid mapping, or kernel fault.
* No dedicated repeated release or refcount +1. `kunmap_local()` ends a temporary virtual mapping but does not release the backing directory page, decrement its lifetime refcount, or free the AFS object.
* No paranoid repeated-refcount +1. There is no second write-like object refcount mutation.
* No FLOOR 5. This is fixed stale mapping storage with no controlled reclaim, structured-object reuse, callback consumption, or second object-lifetime mutation.
* Controlled reclaim and arbitrary or directed kernel writes are not demonstrated.
* Confidentiality and integrity points are not awarded. Corruption of local mapping bookkeeping does not by itself establish disclosure or unauthorized modification.
* Extra Availability is not awarded because it would duplicate the possible kernel-fault consequence.
* Remote reachability is not established. AFS server data can influence directory hash layout, but the vulnerable removal operation is local.
3. Reachability analysis
The practical attacker is a local user allowed to remove an entry from an already mounted writable AFS directory. The relevant entry must not be first in its hash chain so that `afs_dir_find_block()` is called again.
Mounting and configuring AFS may require prior administrative setup, but the attacker does not need to perform that setup when a suitable mount and writable directory are already exposed. The complete vulnerable operation is governed by filesystem permissions rather than a namespace-scoped capability, so `HostAdminRequired=NO` and `NamespaceScopedPrivilege=NO`.
No special race is required. The failure follows an ordered control path involving manual unmap, retention of `iter.block`, and a second block lookup. Actual impact depends on architecture and `kmap_local` implementation. Real high-memory temporary mappings make mapping-stack damage more consequential, but rare physical hardware is not established.
4. Primitive and severity interpretation
The exact primitive is a stale post-unmap mapping reference followed by a second unmap of that reference. It is an equivalent local-mapping lifetime violation, not a demonstrated use-after-free of the backing AFS page.
The stale resource is fixed temporary mapping state rather than an attacker-reclaimable active structured object. The second operation can corrupt per-task local-mapping bookkeeping, but it does not perform a second page or object refcount decrement. Therefore, this is constrained CLASS_B rather than CLASS_A and does not qualify for the concrete repeated release or refcount exception.
The demonstrated mechanism supports invalid mapping state and possible local kernel DoS. Broader memory corruption is technically conceivable on implementations with a real mapping stack, but controlled target selection, arbitrary read or write, disclosure, and privilege escalation are not established.
`ImportantCandidate=NO` because no independently useful exploitation leverage beyond mapping-state corruption and a possible fault is shown. `AutoDowngradeAllowed=YES` because this is a constrained fixed-resource lifetime violation without controlled reuse, object-lifetime mutation, or security-boundary bypass. Operationally it is a borderline Moderate issue that merits architecture-specific review.
5. One-sentence report phrase
AFS directory removal can retain an already unmapped directory block in the iterator and unmap it again during a second hash-chain lookup, potentially corrupting local mapping state and causing a local kernel denial of service.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm behavior of unmatched `kunmap_local()` calls on affected architectures, especially HIGHMEM implementations, to determine whether the consequence is limited to warnings or can produce persistent incorrect mappings or broader memory corruption.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: afs: Fix double-unmap of directory block
Commit: 9d6c703e24da3d39067e3c75f4ac2f6001c2472f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9d6c703e24da3d39067e3c75f4ac2f6001c2472f
Commit description:
Fix afs_edit_dir_remove() to use a cleanup function to unmap the block
pointed to by afs_dir_iter::block if it's left pointing to something rather
than manually kunmapping the blocks. Manually kunmapping without clearing
iter.blocks can result in a double-kunmap if afs_dir_find_block() is called
twice in a row (which would be the case if the block being modified is not
first in the hash chain).
Fixes: a5b5bee ("afs: Use the contained hashtable to search a directory")
Closes: https://sashiko.dev/#/patchset/20260716103030.3065561-1-dhowells%40redhat.com
Signed-off-by: David Howells <[email protected]>
Link: https://patch.msgid.link/[email protected]
cc: Marc Dionne <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner (Amutable) <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
fs/afs/dir_edit.c
fs/afs/dir_search.c
fs/afs/internal.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=9d6c703e24da3d39067e3c75f4ac2f6001c2472f
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97585 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97585
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: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: 3
Paranoid ActionableScore: 4
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 REGULAR
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-09-25 17:36 21% [CVE-2026-97585][MODERATE REGULAR] afs: Fix double-unmap of directory block AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox