* [CVE-2026-90150][MODERATE 7.0] pnfs/blocklayout: Fix device leaks on parse failure [ Upstream
@ 2026-09-17 17:26 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-17 17:26 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90150
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: pnfs/blocklayout: Fix device leaks on parse failure [ Upstream
Commit: 8a2494964edac2a13e82441c2bf887548dc3be0b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8a2494964edac2a13e82441c2bf887548dc3be0b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90150
Analysis date: Thu, 17 Sep 2026 13:26:22 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate
Manual review required: YES
Summary:
A malicious NFS/pNFS server can supply malformed blocklayout device metadata that triggers partial parse cleanup bugs, including leaked child devices and a double `fput()` on `bdev_file`, creating a client-side kernel DoS and an unresolved UAF-style lifetime corruption risk.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90150 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90150
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.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-90150 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90150 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H';*CWE-772;*CWE-401;*CWE-416;Other CVSS 'AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'NFS pNFS blocklayout device parsing can leak device references and can leave a released bdev_file pointer reachable after an error path. A malicious or compromised NFS server can potentially trigger this by returning crafted GETDEVICEINFO data that makes concat stripe or scsi parsing fail after partial initialization. For the CVSS the PR:N because the attacker does not need an account on the client, but the scenario usually requires control of the NFS server or the network path used by the mounted pNFS export. The issue is network reachable from the server side to the NFS client, but it is not a generic Internet exposed listener on the victim. Impact is at least denial of service through resource leaks or a kernel crash, and the double fput cleanup path makes a UAF style memory corruption risk plausible enough for manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7) YES DISK INIT SIMPLEFIX LEAK NETWORK HARDWARE LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH NO NO checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=7
ActionableScoreLower=6
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
## 1. ActionableScore
* Raw conservative score: 6
* Conservative score: 6
* Raw paranoid score: 7
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate**::
No floor or cap changed the score.
## 2. Signal breakdown
Positive signals:
* +2 Real UAF / lifetime violation: `bl_parse_scsi()` can call `fput(d->bdev_file)` on an error path while leaving `d->bdev_file` non-NULL, allowing an outer cleanup path to call `fput()` again on the same reference.
* +1 Concrete repeated release/refcount operation: the first `fput()` can drop the final file reference, the exact same `d->bdev_file` pointer survives, and a later `bl_free_device()` path can perform another lifetime-affecting `fput()` on it.
* +1 Concrete persistent resource/reference leak: concat/stripe parsing can allocate `children`, fail before `nr_children` is incremented, and then skip freeing the child array and parsed child resources.
* +1 Reliable kernel crash / strong DoS: double `fput()` on a potentially freed `struct file` and persistent kernel resource leakage can realistically cause kernel fault, refcount corruption symptoms, or resource exhaustion.
* +2 Remote/client-side network reachability: crafted pNFS `GETDEVICEINFO` / blocklayout metadata can be supplied by a malicious or compromised NFS/pNFS server to the client.
* -1 Specialized deployment / prerequisite: practical reachability depends on the victim using NFS pNFS blocklayout and processing server-supplied block device layout metadata. This is not a generic Internet-exposed listener.
Paranoid-only signal:
* +1 Paranoid repeated-refcount leverage: the second `fput()` is not merely a stale read. It is a concrete write-like lifetime/refcount mutation through storage whose original `struct file` lifetime may already have ended.
Important non-awarded signals:
* Controlled reclaim is not demonstrated.
* Arbitrary kernel read/write is not demonstrated.
* Callback or function pointer control is not demonstrated.
* Confidentiality and integrity impact are not awarded as separate scoring signals because no concrete disclosure, overwrite target, credential manipulation, or protected-object modification is shown.
* Structured stale-object leverage is not separately awarded because the relevant exploitation concern is already counted as concrete repeated `fput()` / refcount mutation.
* Weak LPE is not separately awarded for the same repeated-release fact.
* Extra availability is not awarded because the same crash/resource-failure consequence is already counted once.
* CLASS_A is not used because the patch does not establish controlled reclaim, directed corruption, privilege escalation, or arbitrary R/W.
Repeated-release checks:
* First release can end lifetime: yes, `fput()` can drop the final `struct file` reference.
* Exact same reference survives: yes, the patch explicitly clears `d->bdev_file = NULL` after `fput()`, indicating the same pointer could otherwise remain reachable.
* Second operation mutates lifetime/refcount: yes, later cleanup can call `fput()` again.
* +1 Concrete repeated release/refcount awarded: yes.
* Paranoid repeated-refcount leverage +1 awarded: yes.
* FLOOR 5 applied: not needed, raw conservative score is already 6.
## 3. Reachability analysis
The plausible attacker is a malicious or compromised NFS/pNFS server, or an attacker able to tamper with the server-to-client metadata path. The vulnerable parser consumes server-supplied pNFS blocklayout device data during `GETDEVICEINFO` handling.
Host administrator privileges on the victim are not required by the attacker once the client is already configured to use the relevant NFS/pNFS export. However, the environment normally requires prior legitimate client-side NFS/pNFS setup. This is treated as a deployment prerequisite, not as attacker host-admin requirement.
This is not namespace-scoped. No relevant namespace capability path is established.
The trigger is not a local syscall-only path. It is client-side network parsing of storage layout metadata from the NFS/pNFS server. Practical exposure is narrower than a public TCP listener because the client must mount or otherwise use a pNFS blocklayout-capable export.
No special physical hardware requirement is established beyond use of the pNFS blocklayout feature. No race or narrow timing window is required. The bug is an ordered error-path cleanup/lifetime bug, not a timing race.
## 4. Primitive and severity interpretation
The exact primitive is a combination of:
* persistent resource/reference leak on partially initialized concat/stripe child devices;
* concrete double `fput()` / lifetime violation on `d->bdev_file`.
The `bdev_file` case is stronger than an ordinary cleanup stale dereference. It is category B from the repeated-lifetime distinction:
A. ordinary stale cleanup dereference: not the main concern here.
B. second lifetime/refcount mutation through a potentially dangling object: established. The first `fput()` may end the `struct file` lifetime, the stale pointer remains stored in `d->bdev_file`, and a later cleanup can perform another `fput()` on that same pointer.
This is `PrimitiveClass=CLASS_B`: a real kernel lifetime/refcount corruption primitive exists, but controlled reclaim, arbitrary R/W, or demonstrated LPE is not established.
Demonstrated consequence is DoS through leaks, cleanup corruption, or kernel crash. Speculative consequence is broader memory corruption or privilege escalation if the double `fput()` can be shaped into useful post-free refcount/object corruption, but that is not proven by the patch.
`ImportantCandidate=YES` because a concrete second lifetime/refcount mutation on a potentially freed `struct file` remains materially unresolved and is reachable through attacker-supplied pNFS metadata.
`AutoDowngradeAllowed=NO` because automatically treating this as an ordinary resource leak would lose the meaningful double-release / UAF-style primitive.
Likely operational severity: actionable moderate at minimum, with strong Important-candidate review justified due to network-supplied metadata plus concrete repeated lifetime mutation.
## 5. One-sentence report phrase
A malicious NFS/pNFS server can supply malformed blocklayout device metadata that triggers partial parse cleanup bugs, including leaked child devices and a double `fput()` on `bdev_file`, creating a client-side kernel DoS and an unresolved UAF-style lifetime corruption risk.
## 6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: the patch establishes a concrete repeated lifetime/refcount mutation on the same potentially dangling `struct file` reference, not just a simple leak or crash-only invalid dereference.
## 7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: pnfs/blocklayout: Fix device leaks on parse failure [ Upstream
Commit: 8a2494964edac2a13e82441c2bf887548dc3be0b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8a2494964edac2a13e82441c2bf887548dc3be0b
Changed files:
fs/nfs/blocklayout/dev.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=8a2494964edac2a13e82441c2bf887548dc3be0b
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90150 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90150
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:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7.5
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: 6
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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