CVE-2026-98779 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu: fix ACP MFD device leak on init failure
acp_hw_init() registers ACP child devices with mfd_add_devices() before attaching them to the ACP power domain and initializing the hardware.
If attaching a child to the power domain fails, or if the ACP reset or clock enable operation times out, the failure path frees only the source cell, resource, and platform-data allocations. The child platform devices already registered by mfd_add_devices() remain registered and are never released.
Remove the children from the power domain and unregister the MFD devices on failures that occur after mfd_add_devices() succeeds. Keep mfd_add_devices() failures on the existing cleanup path since the MFD core already rolls back partially registered children itself.
The issue was identified by a static analysis tool I developed and confirmed by manual review.
(cherry picked from commit 63da68d6a2279ec945581c990c5a59a5ae8b5560)
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Analysis
by VulDB Data Team • 10/19/2026
The Linux kernel driver for AMD GPU hardware, specifically the Audio Co-Processor subsystem within the amdgpu module, contains a resource management flaw that leads to device leaks during initialization failures. This vulnerability arises from an inconsistent cleanup sequence in the acp_hw_init function, which is responsible for setting up the ACP hardware components. The core of the issue lies in the order of operations and the handling of error paths when registering Multi-Function Device children using mfd_add_devices. During normal operation, this function registers child devices with the multi-function device core before attempting to attach them to a power domain or initializing their clocks and resets. This architectural decision is intended to ensure that hardware resources are properly accounted for by the kernel's device model early in the process. However, when subsequent steps such as attaching to the power domain or enabling clocks fail due to timeouts or other errors, the existing error handling logic only frees the source cell, resource structures, and platform data allocations associated with the parent context. It fails to address the child platform devices that have already been registered with the MFD core.
This oversight results in a persistent leak of device objects within the kernel's internal data structures. Because mfd_add_devices registers these children with the system, they become visible to the rest of the operating system and are tracked by the driver model subsystems. When the initialization fails but the cleanup routine does not explicitly unregister these child devices, they remain in a registered state without being properly released or destroyed. Over time, particularly on systems where GPU drivers are frequently loaded and unloaded or re-initialized due to hardware resets or configuration changes, this can lead to an accumulation of orphaned device structures. While this may not immediately cause a system crash, it represents a significant resource leak that degrades kernel memory efficiency and can eventually contribute to instability if the number of leaked objects grows large enough to impact other subsystems or exhaust available identifiers for new devices.
From a security and stability perspective, this vulnerability aligns with CWE-401, which describes a missing release of memory after successful allocation, specifically in the context of kernel object management rather than simple heap memory. The failure to properly clean up registered device structures means that references held by the MFD core are not dereferenced or removed from internal lists. This can complicate debugging efforts and make it difficult for system administrators to identify which components are consuming resources unnecessarily. Furthermore, in scenarios where an attacker might induce repeated initialization failures through malicious hardware interaction or specific driver triggers, this leak could be exploited as a denial-of-service vector by gradually exhausting kernel memory reserves dedicated to device management structures. The lack of proper teardown also violates the principle of least privilege and robust resource handling expected in secure system design, as it leaves dangling references that could potentially interfere with subsequent initialization attempts or other drivers interacting with similar hardware resources.
The remediation for this issue involves modifying the error handling paths within acp_hw_init to ensure symmetry between registration and deregistration operations. When mfd_add_devices succeeds but a subsequent step such as power domain attachment or clock enablement fails, the code must now explicitly remove the children from their respective power domains and unregister them using the appropriate MFD core functions. This ensures that all references held by the kernel are properly released, returning the system to a clean state before reporting the initialization failure. It is important to note that this fix does not alter behavior for failures occurring during mfd_add_devices itself, as the MFD core already handles rollback of partially registered children in those cases automatically. By addressing only the post-registration errors, the patch maintains compatibility with existing kernel behaviors while closing the specific gap identified by static analysis tools and manual code review.
To mitigate similar vulnerabilities in other parts of the Linux kernel or third-party drivers, developers should adhere to strict resource management protocols that mirror allocation patterns during cleanup routines. This includes ensuring that every call to a registration function like mfd_add_devices is paired with a corresponding deregistration call on all error paths where it succeeded. Adhering to ATT&CK techniques related to resource exhaustion and persistence mechanisms can help security teams identify such flaws by monitoring for unusual growth in kernel object counts or driver-specific metrics during stress testing. Organizations should also prioritize static analysis tools that track state transitions across initialization sequences, as these are effective at identifying mismatches between setup and teardown logic. Regular code audits focusing on error handling paths, particularly those involving hardware interaction and power management subsystems, remain critical for maintaining the integrity and stability of kernel-level software components.