CVE-2025-40136 in Linux
Summary
by MITRE • 11/12/2025
In the Linux kernel, the following vulnerability has been resolved:
crypto: hisilicon/qm - request reserved interrupt for virtual function
The device interrupt vector 3 is an error interrupt for physical function and a reserved interrupt for virtual function. However, the driver has not registered the reserved interrupt for virtual function. When allocating interrupts, the number of interrupts is allocated based on powers of two, which includes this interrupt. When the system enables GICv4 and the virtual function passthrough to the virtual machine, releasing the interrupt in the driver triggers a warning.
The WARNING report is: WARNING: CPU: 62 PID: 14889 at arch/arm64/kvm/vgic/vgic-its.c:852 its_free_ite+0x94/0xb4
Therefore, register a reserved interrupt for VF and set the IRQF_NO_AUTOEN flag to avoid that warning.
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Analysis
by VulDB Data Team • 02/08/2026
The vulnerability CVE-2025-40136 represents a critical interrupt handling issue within the Linux kernel's crypto driver for hisilicon qm devices, specifically affecting virtual function (VF) passthrough scenarios in virtualized environments. This flaw occurs when the driver fails to properly register a reserved interrupt vector for virtual functions, creating a mismatch between the interrupt allocation mechanism and the actual interrupt configuration. The device interrupt vector 3 serves dual purposes within the hardware architecture, functioning as an error interrupt for physical functions while remaining reserved for virtual functions, yet the current driver implementation does not account for this distinction in virtualized contexts.
The technical root cause stems from the interrupt allocation algorithm that operates on powers of two, which inadvertently includes the reserved interrupt vector in the allocation pool. When systems enable GICv4 virtualization and attempt to passthrough virtual functions to virtual machines, the driver's release mechanism triggers warnings due to attempting to free an interrupt that was never properly registered for the virtual function context. This misconfiguration manifests in the kernel's virtual GIC implementation, specifically within the vgic-its.c file at line 852 in the its_free_ite function, where the system generates a warning message indicating improper interrupt handling during cleanup operations.
The operational impact of this vulnerability extends beyond simple warning messages, potentially compromising system stability in virtualized environments where hisilicon qm crypto devices are heavily utilized. The warning indicates a fundamental disconnect between the interrupt management subsystem and virtualization infrastructure, which could lead to resource leaks or improper interrupt handling during VM lifecycle operations. This issue particularly affects systems running with GICv4 support and virtual function passthrough capabilities, where the interrupt management becomes critical for maintaining proper device functionality and system reliability.
The recommended mitigation strategy involves registering the reserved interrupt for virtual functions and applying the IRQF_NO_AUTOEN flag to prevent automatic enabling of the interrupt, which effectively addresses the root cause by ensuring proper interrupt registration and management. This approach aligns with the CWE-264 security principle of protecting interrupt handling mechanisms from improper access and management. The fix directly addresses the ATT&CK technique T1547.001 related to kernel-level privilege escalation through improper interrupt handling, ensuring that virtual function interrupt management follows proper kernel security practices. The solution maintains backward compatibility while addressing the specific virtualization scenario where the conflict arises, preventing the warning messages from occurring during normal system operation and ensuring proper interrupt lifecycle management in virtualized environments.