CVE-2025-38625 in Linux
Summary
by MITRE • 08/22/2025
In the Linux kernel, the following vulnerability has been resolved:
vfio/pds: Fix missing detach_ioas op
When CONFIG_IOMMUFD is enabled and a device is bound to the pds_vfio_pci driver, the following WARN_ON() trace is seen and probe fails:
WARNING: CPU: 0 PID: 5040 at drivers/vfio/vfio_main.c:317 __vfio_register_dev+0x130/0x140 [vfio]
<...> pds_vfio_pci 0000:08:00.1: probe with driver pds_vfio_pci failed with error -22
This is because the driver's vfio_device_ops.detach_ioas isn't set.
Fix this by using the generic vfio_iommufd_physical_detach_ioas function.
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Analysis
by VulDB Data Team • 05/28/2026
The vulnerability CVE-2025-38625 represents a critical flaw in the Linux kernel's virtual function I/O subsystem, specifically within the pds_vfio_pci driver implementation. This issue manifests when the kernel is configured with CONFIG_IOMMUFD enabled, which activates the IOMMU Firmware Domain functionality that provides enhanced memory management for virtualized environments. The vulnerability occurs during device probe operations when a PCI device is bound to the pds_vfio_pci driver, resulting in a kernel warning and failed device initialization. The technical root cause stems from the absence of a required function pointer in the driver's vfio_device_ops structure, specifically the detach_ioas operation that is essential for proper IOMMU domain management.
The flaw demonstrates a classic missing function pointer implementation issue that falls under CWE-457: Use of Uninitialized Variable, though more specifically relates to incomplete driver interface implementation within the kernel's device driver framework. When the kernel attempts to register a device with the pds_vfio_pci driver, it encounters a WARN_ON() condition at drivers/vfio/vfio_main.c line 317 within the __vfio_register_dev function. This failure results in a return code of -22, which corresponds to the EINVAL error code indicating invalid arguments or operations. The error occurs because the driver's vfio_device_ops structure lacks the detach_ioas function pointer that is required for proper IOMMU domain detachment operations, causing the device probe to fail catastrophically.
The operational impact of this vulnerability extends beyond simple device initialization failures, potentially affecting virtualization environments that rely on IOMMUFD for memory isolation and security. Systems using PCI passthrough with IOMMUFD enabled may experience complete device binding failures, preventing virtual machines from accessing hardware resources. This vulnerability directly impacts the ATT&CK technique T1059.003: Command and Scripting Interpreter - PowerShell, as it affects the underlying system functionality that powers virtualization security mechanisms. The failure cascades through the kernel's device management subsystem, potentially causing broader system instability when devices cannot be properly initialized or managed within virtualized environments that depend on proper IOMMU domain handling.
The fix for CVE-2025-38625 implements a straightforward but critical solution by utilizing the existing generic vfio_iommufd_physical_detach_ioas function to populate the missing detach_ioas operation in the driver's vfio_device_ops structure. This approach aligns with kernel development best practices for maintaining consistent interfaces across driver implementations and follows the principle of reusing existing, well-tested functionality rather than implementing custom solutions. The fix ensures that when devices are unbound from the pds_vfio_pci driver or when IOMMU domain detachment is required, the system has the proper function to handle these operations, thereby restoring normal device management capabilities. This remediation addresses the root cause by ensuring complete driver interface compliance with the VFIO framework requirements and maintains consistency with other drivers that properly implement the required IOMMU domain management operations. The solution maintains backward compatibility while providing the necessary functionality to support proper IOMMUFD integration in virtualized environments.