* [CVE-2026-89449][LOW] iommu: Fix dev_iommu memory leak when device_add fails in iommu_mock_device_add
@ 2026-09-11 23:14 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-11 23:14 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89449
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: iommu: Fix dev_iommu memory leak when device_add fails in iommu_mock_device_add
Commit: f80f3acb69164800051ecdee871b6b006cbc2e66
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f80f3acb69164800051ecdee871b6b006cbc2e66
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89449
Analysis date: Fri, 11 Sep 2026 19:14:28 -0400
ActionableScore: 2
ActionableScore lower bound: 1
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-2026-89449 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89449
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-2026-89449 LOW https://www.kernelcve.org/list/?q=CVE-2026-89449 CHECK WITH IMPACT FROM ORIG NN LOW 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-401;*CWE-772;CWE-459;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A memory leak in iommu_mock_device_add can occur when iommu_fwspec_init allocates dev iommu and fwspec but device_add() later fails. The old error path released only fwspec and left the outer dev_iommu object allocated, so repeated failures can slowly consume kernel memory. For the CVSS the PR:L is used because a local process with access to the iommufd selftest or mock device ioctl path is needed for practical triggering. The issue is not network reachable and is limited to local control plane activity. Impact is denial of service through resource exhaustion only. No evidence of UAF, OOB access, arbitrary write, information disclosure, or privilege escalation is visible from the code path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES INIT LEAK ERRORPATH HARDWARE YES NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Conservative signals:
* +1 Concrete persistent kernel resource/reference leak. `iommu_fwspec_init()` allocates `dev->iommu` and `dev->iommu->fwspec`, but the old `device_add()` failure path released only `fwspec`, leaving the outer `dev_iommu` object permanently allocated.
* 0 Reliable kernel crash not awarded. The supplied evidence shows `kmemleak`, not panic, Oops, UAF, or immediate host-wide failure.
* 0 C/I impact not awarded. No information disclosure, unauthorized modification, UAF, OOB access, arbitrary write, or security-boundary bypass is established.
* 0 Privilege penalty not applied. Host-admin-equivalent privilege is not positively established, but below-host-admin reachability is also not fully proven.
Paranoid additional signal:
* +1 Potential resource exhaustion by sustained repetition. Repeated successful reach of the `device_add()` failure path could accumulate leaked kernel allocations, but this remains resource-exhaustion only and does not justify Important-level scoring.
Important non-awarded signals:
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* UAF not demonstrated.
* Concrete repeated release/refcount mutation not established.
* Remote reachability not established.
* Authorization or security-boundary bypass not established.
* Extra availability beyond possible sustained resource exhaustion not established.
Repeated-release/refcount check:
* First release can end lifetime: only for `fwspec`, not for the leaked outer `dev_iommu`.
* Exact same reference survives to a second lifetime-mutating operation: no.
* Second operation mutates lifetime/refcount: no.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage awarded: no.
* FLOOR 5 applied: no.
3. Reachability analysis
The observed path is through `iommufd` selftest/mock-device handling, ending in `iommu_mock_device_add()`. A local process reaches it through an ioctl path in the supplied stack trace, but the supplied evidence does not fully establish whether this is available to an ordinary unprivileged user, a restricted test-capable user, or only a privileged/debug configuration. Therefore `HostAdminRequired=UNKNOWN`, not YES or NO.
No namespace-scoped capability path is established. There is no network trigger. No special physical hardware is required by the shown mock-device path, but the vulnerable path appears tied to test/mock IOMMU functionality rather than a broad default runtime path. No race or narrow timing condition is involved. The trigger is an ordered error path: initialize fwspec and dev_iommu, then fail `device_add()`, then execute incomplete cleanup.
4. Primitive and severity interpretation
The exact primitive is a missing cleanup of a kernel allocation/reference on an error path. It is a persistent resource leak, not memory corruption. The leaked object is `dev->iommu`, allocated through `dev_iommu_get()`, while the old cleanup called only `iommu_fwspec_free()`.
This is not active structured UAF and not fixed stale storage. No dangling pointer use is shown. No second `put`, `free`, or refcount mutation occurs on a potentially freed object. The demonstrated consequence is kmemleak-detected kernel memory leakage. The speculative consequence is local DoS through repeated accumulation, but no immediate crash or exploit primitive beyond resource consumption is established.
Primitive class is `NONE` because no meaningful corruption, ownership violation, authorization bypass, or post-lifetime object use is established. `ImportantCandidate=NO` because this is a constrained resource leak without unresolved memory-corruption leverage. `AutoDowngradeAllowed=YES` because automatic downgrade would not discard a concrete UAF, boundary bypass, or stronger exploitation primitive.
Likely operational severity is Low to ordinary Moderate, depending on whether the selftest/mock path is reachable in the evaluated product.
5. One-sentence report phrase
A memory leak in `iommu_mock_device_add()` can leave `dev_iommu` allocated when `device_add()` fails, allowing possible local resource exhaustion through repeated error-path triggering but showing no UAF, memory corruption, information disclosure, or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
Reason: the patch establishes a concrete memory leak only, with no UAF, repeated release/refcount mutation, arbitrary write, authorization bypass, or network exposure.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: iommu: Fix dev_iommu memory leak when device_add fails in iommu_mock_device_add
Commit: f80f3acb69164800051ecdee871b6b006cbc2e66
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f80f3acb69164800051ecdee871b6b006cbc2e66
Commit description:
iommu_mock_device_add() first calls iommu_fwspec_init(), which on
success allocates both dev->iommu (via dev_iommu_get()) and
dev->iommu->fwspec. If the subsequent device_add(dev) call fails,
the error path only calls iommu_fwspec_free(dev), which frees
fwspec but leaves dev->iommu still allocated.
This triggers the following kmemleak report when fuzzing with Syzkaller:
BUG: memory leak
unreferenced object 0xffff888011e0a200 (size 192):
comm "syz.1.1695", pid 24885, jiffies 4295222527
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 ad 4e ad de .............N..
ff ff ff ff 00 00 00 00 ff ff ff ff ff ff ff ff ................
backtrace (crc 25df5bb3):
kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
slab_post_alloc_hook mm/slub.c:4575 [inline]
slab_alloc_node mm/slub.c:4899 [inline]
__kmalloc_cache_noprof+0x47a/0x710 mm/slub.c:5415
kmalloc_noprof include/linux/slab.h:950 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
dev_iommu_get+0x10c/0x1a0 drivers/iommu/iommu.c:408
iommu_fwspec_init+0x288/0x4d0 drivers/iommu/iommu.c:3087
iommu_mock_device_add+0x46/0xb0 drivers/iommu/iommu.c:385
mock_dev_create drivers/iommu/iommufd/selftest.c:1025 [inline]
iommufd_test_mock_domain drivers/iommu/iommufd/selftest.c:1066 [inline]
iommufd_test+0x2f8a/0x6190 drivers/iommu/iommufd/selftest.c:2072
iommufd_fops_ioctl+0x367/0x540 drivers/iommu/iommufd/main.c:533
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+0x18e/0x210 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Fix this by calling dev_iommu_free(dev) instead of iommu_fwspec_free(dev)
in the device_add() failure path. dev_iommu_free() frees both fwspec
and the outer dev_iommu struct and clears dev->iommu.
Link: https://patch.msgid.link/r/76AC62D46B998556+20260711055119.1003477-1-peiyang_he@smail.nju.edu.cn
Reported-by: Peiyang He <[email protected]>
Fixes: 2a91891 ("iommufd: Register iommufd mock devices with fwspec")
Cc: [email protected]
Signed-off-by: Peiyang He <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
include/linux/kmemleak.h
mm/slub.c
include/linux/slab.h
drivers/iommu/iommu.c
drivers/iommu/iommufd/selftest.c
drivers/iommu/iommufd/main.c
fs/ioctl.c
arch/x86/entry/syscall_64.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=f80f3acb69164800051ecdee871b6b006cbc2e66
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89449 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89449
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
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please use reply email interface to add additional manual analyses
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And please, please, let me know when you see Lows instead of Importants
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My contact email for such notifications is [email protected] (and both
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