From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98178][LOW] drm/amdgpu: Skip KFD mapping clear before initialization Date: Thu, 08 Oct 2026 07:57:29 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98178 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: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 157d3f1db7e7e6f320daa221fae84a4c13555b6f List-Id: CVE: CVE-2026-98178 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: drm/amdgpu: Skip KFD mapping clear before initialization Commit: 157d3f1db7e7e6f320daa221fae84a4c13555b6f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=157d3f1db7e7e6f320daa221fae84a4c13555b6f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98178 Analysis date: Thu, 08 Oct 2026 07:57:29 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: An AMDGPU KFD initialization failure can leave a partially initialized device state that causes a NULL-pointer dereference during a later GPU reset, resulting in a local denial of service without demonstrated memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98178 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98178 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-2026-98178 LOW https://www.kernelcve.org/list/?q=CVE-2026-98178 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW) 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-665;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'The supplied source contains only the abbreviated stable commit ID 7f9caa7. The analysis is based on the shown commit message and diff. Reassess manually if a report demonstrates GPU reset triggering without local render or compute access, or any memory corruption beyond the shown NULL dereference.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE INIT SIMPLEFIX HARDWARE INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 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**:: No floor or cap was applied. The paranoid interpretation cannot defensibly add a reachability or corruption point because the supplied patch establishes only an uninitialized pointer dereference after a failed KFD initialization and later GPU reset. ## 2. Signal breakdown * +1 Reliable kernel fault or strong DoS. The commit directly describes a later GPU reset dereferencing `nodes[0]->id` when `nodes[0]` was never allocated. This can produce a kernel NULL-pointer dereference and an Oops or crash. Important non-awarded signals: * No real UAF. `kfd_dev` remains allocated and attached. The invalid object state is that its `nodes[0]` member was never initialized. There is no freed object, dangling reference, or post-lifetime use. * No repeated release or refcount mutation. The vulnerable path walks the node array and dereferences an uninitialized entry. It does not perform a second `put`, `free`, or refcount operation on a potentially freed object. * No controlled reclaim, object replacement, arbitrary write, OOB access, callback control, or attacker-shaped post-free data is established. * No confidentiality or integrity signal. The patch supports a NULL-pointer dereference, not information disclosure or unauthorized modification. * No local-unprivileged-trigger point. The supplied evidence does not establish that an ordinary local user can cause the required GPU reset after the failed KFD initialization. * No host-admin penalty. Host-admin-equivalent privilege is not positively established as required for the complete reset trigger. * No rare-hardware penalty. Polaris hardware and missing PCIe atomics support are configuration and platform conditions, but the evidence does not establish genuinely rare physical-only access requirements. * No remote-reachability point. Network input does not reach this path. ## 3. Reachability analysis The vulnerable state is created when KFD initialization fails after probe. The described example is a Polaris GPU without required PCIe atomics support. `num_nodes` is already set, but `nodes[0]` is not allocated, while `kfd_dev` remains attached to the AMDGPU device. A later GPU reset reaches `amdgpu_amdkfd_clear_kfd_mapping()` and dereferences the uninitialized node pointer. The patch does not show what actor can reliably initiate that reset. It may occur through driver recovery, GPU hang handling, display operations, or privileged device management, but none of those complete paths is established in the supplied context. A logged-in graphical user, DRM render client, DRM master, compositor, delegated graphics service, and host administrator have materially different permissions. The supplied patch does not prove that any below-host-admin actor can trigger the complete sequence. Therefore: * HostAdminRequired is `UNKNOWN`. * NamespaceScopedPrivilege is `UNKNOWN`. * No ordinary-user or delegated-capability reachability bonus is applied. * No host-admin penalty is applied either, because host-admin privilege is not positively proven. The issue is not network reachable. No namespace-specific capability check or attacker-created namespace path is relevant in the supplied evidence. ## 4. Primitive and severity interpretation The exact primitive is a NULL-pointer dereference caused by an initialization-state mismatch: `kfd_dev exists` `num_nodes is nonzero` `nodes[0] was never allocated` `GPU reset walks nodes[0]` `kernel dereferences nodes[0]->id` This is not an active-object lifetime violation. `kfd_dev` has not been freed, and the pointer is not stale after object lifetime termination. The node array entry is simply absent because initialization failed before node allocation. The vulnerable operation is neither a destructor UAF nor a repeated lifetime/refcount mutation. It is a direct invalid-state dereference during KFD mapping cleanup before KFD initialization completed. The demonstrated consequence is local denial of service through a kernel fault during GPU reset. A GPU-only disruption may also be possible depending on kernel Oops and panic policy, but no stronger host integrity, confidentiality, or privilege-escalation primitive is supported. The primitive is therefore `CLASS_C`. It is not a meaningful Important candidate because no memory corruption, controlled reuse, active-object lifetime corruption, security-boundary bypass, or privilege-escalation mechanism is established. Automatic downgrade is allowed because the available evidence supports a constrained crash/DoS condition only. ## 5. One-sentence report phrase An AMDGPU KFD initialization failure can leave a partially initialized device state that causes a NULL-pointer dereference during a later GPU reset, resulting in a local denial of service without demonstrated memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch and commit message establish a deterministic NULL-pointer dereference in a partially initialized KFD state, but do not establish a UAF, arbitrary memory access, privilege-boundary bypass, or below-host-admin trigger path requiring escalation review. ## 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu: Skip KFD mapping clear before initialization Commit: 157d3f1db7e7e6f320daa221fae84a4c13555b6f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=157d3f1db7e7e6f320daa221fae84a4c13555b6f Commit description: amdgpu_amdkfd_clear_kfd_mapping() assumes that a non-NULL kfd_dev has a fully populated node array. This is not true when KFD device initialization fails after probe. For example, kgd2kfd_device_init() sets num_nodes before checking PCIe atomics support. On Polaris systems without the required atomics, it returns before allocating nodes[0], but the kfd_dev remains attached to the amdgpu device. A later GPU reset then dereferences nodes[0]->id. Require the authoritative KFD initialization flag before walking the node array, matching the existing KFD reset and teardown paths. Fixes: 70cadef ("drm/amdgpu: unmap all user mappings of framebuffer and doorbell before mode1 reset") Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5833 Reviewed-by: Alex Deucher Signed-off-by: Mario Limonciello Signed-off-by: Alex Deucher (cherry picked from commit 4ac1835 ) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.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=157d3f1db7e7e6f320daa221fae84a4c13555b6f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98178 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98178 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: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 alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).