From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89449][LOW] iommu: Fix dev_iommu memory leak when device_add fails in iommu_mock_device_add Date: Fri, 11 Sep 2026 19:14:28 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89449 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: f80f3acb69164800051ecdee871b6b006cbc2e66 List-Id: 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 Fixes: 2a91891 ("iommufd: Register iommufd mock devices with fwspec") Cc: stable@vger.kernel.org Signed-off-by: Peiyang He Signed-off-by: Jason Gunthorpe Signed-off-by: Greg Kroah-Hartman 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 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 alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).