* [CVE-2026-98517][MODERATE 7.0] drm/nouveau/uvmm: fix UAF in nouveau_uvmm_sm when BO is in TTM_PL_SYSTEM
@ 2026-10-24 12:13 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-24 12:13 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98517
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/nouveau/uvmm: fix UAF in nouveau_uvmm_sm when BO is in TTM_PL_SYSTEM
Commit: 1245b4b43da67596be61600dbd746539c79495ac
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1245b4b43da67596be61600dbd746539c79495ac
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98517
Analysis date: Sat, 24 Oct 2026 08:13:47 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
A local Nouveau render-node client can cause a one-byte slab OOB read through resource type confusion, with the invalid type consumed by GPU mapping code and a demonstrated kernel fault.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98517 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98517
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-2026-98517 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98517 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-125;CWE-843;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'nouveau_uvmm_sm can treat a TTM_PL_SYSTEM resource as struct nouveau_mem even though SYSTEM placement provides only struct ttm_resource. The resulting mem type access reads beyond the resource and can reach freed slab memory during an asynchronous VM_BIND map job. The concrete primitive is an invalid one byte slab read with a demonstrated KASAN use after free report. For the CVSS the PR:L value is selected because an attacker needs local process access to Nouveau DRM ioctls or a render node. AC:H reflects dependence on BO placement, asynchronous scheduler execution, and allocator state. The established impact is a local kernel crash. Limited confidentiality or integrity impact is retained only in the paranoid vector because the invalid type value influences downstream GPU mapping behavior, while no arbitrary write or reliable information disclosure is proven. The issue is not directly network reachable. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 5.8 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage MODERATE_KPANIC to MODERATE because KP specialist did not establish a qualifying panic. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.8 and ActionableScore 4 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE READ OOB DANGER UAF HARDWARE LINUS MEMORY LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 4.
* Conservative score: 4; no floor or cap applied.
* Raw paranoid score: 4.
* Paranoid score: 4; theoretical confidentiality, integrity, or stronger mapping corruption is not scored.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +1 weak/indirect corruption candidate: a valid `struct ttm_resource` is incorrectly interpreted as the larger `struct nouveau_mem`, producing a concrete one-byte slab out-of-bounds read.
* +1 material structured-state consumption: the invalid `mem->mem.type` value is consumed by `nouveau_uvmm_vmm_map()` during an asynchronous GPU mapping operation.
* +1 local below-host-admin trigger: supplied evidence grounds GEM/VM_BIND ioctl access through a Nouveau render-node process.
* +1 reliable kernel crash/DoS: the supplied KASAN trace demonstrates the invalid access in the scheduler worker.
* No UAF floor: there is no stale reference to the BO resource. The KASAN “use-after-free” classification results from the out-of-bounds read landing in an adjacent freed slab region.
* No write, disclosure, controlled reclaim, attacker-selected replacement object, callback control, or authorization bypass is shown. No extra availability point is awarded for the same crash.
* NEW52/B5-R does not apply: there is no retry-accumulated index and no heap OOB write.
3. Reachability analysis
A local process with access to the Nouveau render-node ioctls can create the BO and submit the VM_BIND operation; execution later occurs in a privileged kernel worker. Host UID 0 or host-administrator capability is not indicated as necessary. Device-node access remains an ordinary deployment permission prerequisite, not a namespace capability. Nouveau-supported GPU hardware is required, but the evidence does not establish rare or physical-only hardware. No timing race is proven; asynchronous placement and scheduler state increase trigger complexity but do not justify a separate race penalty.
4. Primitive and severity reading
The exact primitive is a one-byte OOB slab read caused by type confusion between `ttm_resource` and `nouveau_mem`, followed by use of the resulting type value in active GPU mapping logic. It is not a real stale-object UAF and no repeated release/refcount operation exists. This is CLASS_B because malformed structured state reaches a later active consumer, but the demonstrated consequence is a fault/crash. Non-crash mapping corruption remains unresolved rather than proven. Without a write, disclosure, or specific protected-state effect, this is not an Important candidate and may be downgraded after review.
5. One-sentence report phrase
A local Nouveau render-node client can cause a one-byte slab OOB read through resource type confusion, with the invalid type consumed by GPU mapping code and a demonstrated kernel fault.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm non-KASAN behavior and whether invalid mapping-type values can cause effects beyond the demonstrated crash.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: drm/nouveau/uvmm: fix UAF in nouveau_uvmm_sm when BO is in TTM_PL_SYSTEM
Commit: 1245b4b43da67596be61600dbd746539c79495ac
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1245b4b43da67596be61600dbd746539c79495ac
Commit description:
nouveau_uvmm_sm() calls op_map(), which passes bo->resource through
nouveau_mem() to nouveau_uvma_map(). nouveau_uvmm_vmm_map() then reads
mem->mem.type.
But this is only valid when bo->resource is backed by struct nouveau_mem,
as is the case for VRAM and TT resources. If the BO is left in
TTM_PL_SYSTEM, bo->resource is only a struct ttm_resource. Treating it
as struct nouveau_mem makes the mem->mem.type read past the end of the
resource, causing a KASAN: slab-use-after-free Read in nouveau_uvmm_sm
report:
BUG: KASAN: slab-use-after-free in nouveau_uvmm_vmm_map drivers/gpu/drm/nouveau/nouveau_uvmm.c:152 [inline]
BUG: KASAN: slab-use-after-free in nouveau_uvma_map drivers/gpu/drm/nouveau/nouveau_uvmm.c:199 [inline]
BUG: KASAN: slab-use-after-free in op_map drivers/gpu/drm/nouveau/nouveau_uvmm.c:849 [inline]
BUG: KASAN: slab-use-after-free in nouveau_uvmm_sm.constprop.0+0x6ab/0x900 drivers/gpu/drm/nouveau/nouveau_uvmm.c:903
Read of size 1 at addr ffff888127d3e3a0 by task kworker/0:1/11
CPU: 0 UID: 0 PID: 11 Comm: kworker/0:1 Not tainted 7.2.0 #5 PREEMPT(lazy)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: nouveau_sched_wq_2224 drm_sched_run_job_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x95/0xe0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcb/0x5a0 mm/kasan/report.c:482
kasan_report+0xca/0x100 mm/kasan/report.c:595
nouveau_uvmm_vmm_map drivers/gpu/drm/nouveau/nouveau_uvmm.c:152 [inline]
nouveau_uvma_map drivers/gpu/drm/nouveau/nouveau_uvmm.c:199 [inline]
op_map drivers/gpu/drm/nouveau/nouveau_uvmm.c:849 [inline]
nouveau_uvmm_sm.constprop.0+0x6ab/0x900 drivers/gpu/drm/nouveau/nouveau_uvmm.c:903
nouveau_uvmm_sm_unmap drivers/gpu/drm/nouveau/nouveau_uvmm.c:932 [inline]
nouveau_uvmm_bind_job_run+0xd6/0x250 drivers/gpu/drm/nouveau/nouveau_uvmm.c:1532
nouveau_job_run drivers/gpu/drm/nouveau/nouveau_sched.c:350 [inline]
nouveau_sched_run_job+0x62/0xd0 drivers/gpu/drm/nouveau/nouveau_sched.c:364
drm_sched_run_job_work+0x356/0xa10 drivers/gpu/drm/scheduler/sched_main.c:1061
process_one_work+0x8a5/0x1900 kernel/workqueue.c:3322
process_scheduled_works kernel/workqueue.c:3405 [inline]
worker_thread+0x5dd/0xd80 kernel/workqueue.c:3486
kthread+0x31d/0x420 kernel/kthread.c:436
ret_from_fork+0x662/0x940 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Allocated by task 2224 on cpu 0 at 66.550027s:
kasan_save_stack+0x24/0x50 mm/kasan/common.c:57
kasan_save_track+0x17/0x60 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5334 [inline]
__kmalloc_noprof+0x304/0x7c0 mm/slub.c:5359
_kmalloc_noprof include/linux/slab.h:992 [inline]
dma_resv_list_alloc+0x27/0x90 drivers/dma-buf/dma-resv.c:106
dma_resv_reserve_fences+0x60e/0xa30 drivers/dma-buf/dma-resv.c:205
ttm_bo_alloc_resource+0x12c/0xbd0 drivers/gpu/drm/ttm/ttm_bo.c:721
ttm_bo_validate+0x1bc/0x4a0 drivers/gpu/drm/ttm/ttm_bo.c:856
ttm_bo_init_reserved+0x2c3/0x570 drivers/gpu/drm/ttm/ttm_bo.c:970
nouveau_bo_init+0x159/0x2c0 drivers/gpu/drm/nouveau/nouveau_bo.c:359
nouveau_gem_new+0x234/0x5f0 drivers/gpu/drm/nouveau/nouveau_gem.c:272
nouveau_gem_ioctl_new+0x1eb/0x420 drivers/gpu/drm/nouveau/nouveau_gem.c:352
drm_ioctl_kernel+0x192/0x350 drivers/gpu/drm/drm_ioctl.c:817
drm_ioctl+0x4f8/0xb40 drivers/gpu/drm/drm_ioctl.c:914
nouveau_drm_ioctl+0xea/0x2c0 drivers/gpu/drm/nouveau/nouveau_drm.c:1338
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl fs/ioctl.c:583 [inline]
__x64_sys_ioctl+0x180/0x1d0 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x690 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 2223 on cpu 0 at 66.554063s:
kasan_save_stack+0x24/0x50 mm/kasan/common.c:57
kasan_save_track+0x17/0x60 mm/kasan/common.c:78
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x61/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2677 [inline]
[Commit description truncated; see the upstream URL below]
Changed files:
drivers/gpu/drm/nouveau/nouveau_uvmm.c
lib/dump_stack.c
mm/kasan/report.c
drivers/gpu/drm/nouveau/nouveau_sched.c
drivers/gpu/drm/scheduler/sched_main.c
kernel/workqueue.c
kernel/kthread.c
arch/x86/kernel/process.c
arch/x86/entry/entry_64.S
mm/kasan/common.c
include/linux/kasan.h
mm/slub.c
include/linux/slab.h
drivers/dma-buf/dma-resv.c
drivers/gpu/drm/ttm/ttm_bo.c
drivers/gpu/drm/nouveau/nouveau_bo.c
drivers/gpu/drm/nouveau/nouveau_gem.c
drivers/gpu/drm/drm_ioctl.c
drivers/gpu/drm/nouveau/nouveau_drm.c
fs/ioctl.c
arch/x86/entry/syscall_64.c
mm/kasan/generic.c
kernel/rcu/tree.c
kernel/softirq.c
arch/x86/kernel/apic/apic.c
arch/x86/include/asm/idtentry.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=1245b4b43da67596be61600dbd746539c79495ac
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98517 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98517
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:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS score: 5.8
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: unknown
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: 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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