* [CVE-2026-89809][LOW] drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds
@ 2026-09-16 15:02 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-16 15:02 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89809
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds
Commit: 58e866711b234571b0ce342c43d153a4786b32b8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=58e866711b234571b0ce342c43d153a4786b32b8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89809
Analysis date: Wed, 16 Sep 2026 11:02:17 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89809 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89809
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-2026-89809 LOW https://www.kernelcve.org/list/?q=CVE-2026-89809 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference in the AMD KFD debugfs mqds reader occurs because the loop calling mqd_mgr debugfs_show_mqd can execute outside the pqn q validation block. Kernel queue entries can have pqn q set to NULL while only pqn kq is valid, leaving mqd_mgr uninitialized and causing a kernel crash when the mqds debugfs file is read. For the CVSS the PR:H score is used because access to debugfs is normally limited to root or CAP_SYS_ADMIN. The issue is local and is not network reachable. Impact is denial of service through a kernel oops or panic. No information disclosure integrity impact or privilege escalation primitive is supported by the NULL dereference.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) SKIP CVE-2026-89809 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE DANGER NULLPTR HARDWARE DEBUGFS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Reliable kernel crash / strong DoS. The supplied trace establishes a NULL function pointer call through mqd_mgr->debugfs_show_mqd when a kernel queue entry has pqn->q equal to NULL.
* No local unprivileged trigger point awarded. The complete access-control chain for /sys/kernel/debug/kfd/mqds is not established by the patch. The prior hint says debugfs access normally requires root or CAP_SYS_ADMIN, but this is not sufficient evidence of the exact effective permission configuration.
* No remote reachability point awarded. The vulnerable operation is a local debugfs read.
* No UAF or lifetime point awarded. mqd_mgr is NULL due to control-flow scope, not freed, released, replaced, or used after lifetime end.
* No weak or strong exploitation leverage awarded. The dereference targets address zero and the supplied evidence does not establish controlled object substitution, arbitrary write, disclosure, callback influence, or structured post-reuse processing.
* No confidentiality or integrity points awarded. The patch establishes a crash-only NULL dereference and no data disclosure or unauthorized modification primitive.
* No hardware penalty awarded. AMD GPU and KFD are hardware-specific, but the supplied evidence does not establish rare physical access or an unusually inaccessible configuration.
* No host-admin penalty awarded. Host-admin-equivalent privilege is not positively established for the complete trigger path.
3. Reachability analysis
The trigger requires an active KFD queue and a read of the KFD mqds debugfs file. The direct reader is a local process. The supplied material does not establish whether an ordinary user, a graphics service, a delegated debug user, or only a host administrator can access the relevant debugfs file on the evaluated system.
KFD operation requires compatible AMD GPU hardware and the amdgpu KFD functionality to be active. This is a deployment prerequisite, but common AMD GPU hardware is not automatically rare hardware for scoring purposes. No network namespace, user namespace, or namespace-scoped capability path is shown. The complete operation is therefore not established as namespace-scoped.
No race is required. The failure follows deterministic control flow when the queue list contains a kernel queue entry with pqn->q equal to NULL and the mqds debugfs reader processes that entry.
4. Primitive and severity interpretation
The exact primitive is a NULL pointer dereference caused by using mqd_mgr outside the conditional block that initializes it. This is not an active structured stale-object use and not fixed stale storage. No allocation lifetime ends, no object is reused, and no repeated release, put, free, or refcount mutation occurs.
The demonstrated consequence is a kernel Oops or possible panic and resulting local denial of service. A stronger consequence such as privilege escalation, arbitrary kernel read or write, information disclosure, or integrity impact is speculative and unsupported by the patch context.
PrimitiveClass is CLASS_C because the established behavior is invalid-state crash handling without an independently useful corruption primitive. ImportantCandidate is NO because the NULL call does not provide unresolved lifetime, ownership, replacement, authorization, or controlled-corruption leverage. AutoDowngradeAllowed is YES because the issue is a constrained crash-only condition without a concrete memory-corruption or security-boundary primitive.
5. One-sentence report phrase
A local read of the AMD KFD mqds debugfs file can dereference an uninitialized NULL mqd_mgr pointer for kernel queue entries and cause a kernel crash or denial of service.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a deterministic NULL pointer dereference with crash-only impact and does not establish UAF, memory corruption, information disclosure, integrity impact, privilege escalation, or network reachability.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds
Commit: 58e866711b234571b0ce342c43d153a4786b32b8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=58e866711b234571b0ce342c43d153a4786b32b8
Commit description:
Reading /sys/kernel/debug/kfd/mqds while a process holds an active KFD
queue triggers a NULL pointer dereference because the for loop that
calls mqd_mgr->debugfs_show_mqd() is incorrectly placed outside the
if (pqn->q) block that initializes mqd_mgr.
The queue list can contain entries where pqn->q is NULL (kernel queues
where only pqn->kq is valid). In the original code:
if (pqn->q) {
...
mqd_mgr = q->device->dqm->mqd_mgrs[mqd_type];
size = mqd_mgr->mqd_stride(...);
}
for (xcc = 0; xcc < num_xccs; xcc++) { // WRONG: outside if block
mqd = q->mqd + size * xcc;
r = mqd_mgr->debugfs_show_mqd(m, mqd);
}
When iterating over a queue node where pqn->q is NULL:
1. The if (pqn->q) block is skipped
2. mqd_mgr remains uninitialized (NULL from declaration)
3. The for loop executes anyway
4. mqd_mgr->debugfs_show_mqd(m, mqd) dereferences NULL
The crash manifests as:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
RIP: 0010:0x0
Call Trace:
pqm_debugfs_mqds+0x10c/0x1d0 [amdgpu]
kfd_debugfs_mqds_by_process+0x9b/0x110 [amdgpu]
seq_read_iter+0x132/0x4b0
...
Fix by moving the for loop inside the if (pqn->q) block, so mqd_mgr
and related variables are only used when properly initialized.
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5689
Reviewed-by: Alex Deucher <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
(cherry picked from commit 8bfe29d5c798940f797aa24135d2734c3ffce9de)
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.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=58e866711b234571b0ce342c43d153a4786b32b8
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89809 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89809
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:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 5.5
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: unknown
Paranoid ActionableScore: 1
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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