CVE-2023-54034 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
iommufd: Make sure to zero vfio_iommu_type1_info before copying to user
Missed a zero initialization here. Most of the struct is filled with a copy_from_user(), however minsz for that copy is smaller than the actual struct by 8 bytes, thus we don't fill the padding.
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Analysis
by VulDB Data Team • 12/26/2025
The vulnerability CVE-2023-54034 represents a critical initialization flaw within the Linux kernel's iommufd subsystem, specifically affecting the vfio_iommu_type1_info structure handling. This issue resides in the kernel's device virtualization framework that manages IOMMU (Input-Output Memory Management Unit) functionality for virtualized environments. The vulnerability stems from insufficient zero-initialization of the vfio_iommu_type1_info structure before data is copied to user space, creating potential security implications that could be exploited by malicious actors.
The technical flaw manifests in how the kernel handles memory copying operations between kernel and user space contexts. During the copy_from_user operation, the system correctly populates most fields of the vfio_iommu_type1_info structure, but fails to properly initialize the padding bytes within the structure. The copy operation uses a minimum size parameter (minsz) that is deliberately smaller than the complete structure size by exactly 8 bytes, leaving the padding areas uninitialized. This creates a scenario where sensitive data from previous kernel operations could persist in memory regions that should be cleared, potentially exposing confidential information to user-space processes that access this structure.
This vulnerability directly impacts the security posture of Linux systems running virtualized environments, particularly those utilizing VFIO (Virtual Function I/O) drivers for device passthrough. The uninitialized memory could contain kernel stack contents, sensitive configuration data, or remnants of previous operations that might be accessible to unprivileged user processes. The flaw represents a classic information disclosure vulnerability that could be leveraged in combination with other techniques to gain deeper insights into the kernel's internal state, potentially enabling more sophisticated attacks against the system's integrity. The vulnerability aligns with CWE-1289, which describes improper initialization of memory, and could be categorized under ATT&CK technique T1068, involving the exploitation of privilege escalation opportunities through kernel vulnerabilities.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could enable attackers to gather intelligence about the kernel's memory layout and internal structures. In virtualized environments, this could facilitate attacks against the hypervisor or guest operating systems, potentially leading to privilege escalation or data compromise. The vulnerability affects systems that utilize IOMMU functionality for device virtualization, particularly those implementing VFIO-based device passthrough mechanisms. Mitigation strategies should focus on applying the kernel patch that ensures proper zero-initialization of the structure before user-space copy operations, along with implementing monitoring for unusual memory access patterns that might indicate exploitation attempts. Additionally, system administrators should ensure that virtualization environments are properly hardened and that unnecessary device passthrough capabilities are disabled to minimize the attack surface.