CVE-2025-38314 in Linux
Summary
by MITRE • 07/10/2025
In the Linux kernel, the following vulnerability has been resolved:
virtio-pci: Fix result size returned for the admin command completion
The result size returned by virtio_pci_admin_dev_parts_get() is 8 bytes larger than the actual result data size. This occurs because the result_sg_size field of the command is filled with the result length from virtqueue_get_buf(), which includes both the data size and an additional 8 bytes of status.
This oversized result size causes two issues: 1. The state transferred to the destination includes 8 bytes of extra data at the end. 2. The allocated buffer in the kernel may be smaller than the returned size, leading to failures when reading beyond the allocated size.
The commit fixes this by subtracting the status size from the result of virtqueue_get_buf().
This fix has been tested through live migrations with virtio-net, virtio-net-transitional, and virtio-blk devices.
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Analysis
by VulDB Data Team • 12/07/2025
The vulnerability identified as CVE-2025-38314 resides within the Linux kernel's virtio-pci subsystem, specifically affecting how administrative command completions are processed. This issue demonstrates a classic buffer management flaw that can lead to both data corruption and potential security implications within virtualized environments. The vulnerability impacts the virtio-pci driver's handling of admin commands, which are essential for communication between virtual devices and their host controllers. When processing administrative responses, the kernel incorrectly calculates the result size by including additional status bytes that should not be part of the actual data payload. This miscalculation stems from the improper assignment of the result_sg_size field, which captures the complete buffer length returned by virtqueue_get_buf() rather than just the data portion.
The technical flaw manifests as an 8-byte offset error in the result size calculation, where the status information that is typically 8 bytes in size gets inadvertently included in the data size returned to callers. This discrepancy creates a fundamental mismatch between the expected data size and the actual buffer allocation, particularly affecting the virtio_pci_admin_dev_parts_get() function. The issue follows CWE-129 principles related to improper validation of buffer sizes and demonstrates characteristics consistent with improper input validation patterns that can lead to buffer overflows or underflows. The vulnerability specifically impacts the virtio-pci implementation where administrative commands are processed through the virtqueue mechanism, making it particularly relevant for virtualized networking and storage environments that rely on virtio interfaces.
The operational impact of this vulnerability extends beyond simple data corruption to potentially compromise system stability during live migration operations and device management scenarios. When the oversized result size is returned, it causes state transfer mechanisms to include 8 bytes of extraneous data at the end of the result buffer, which can lead to unpredictable behavior in the receiving components. More critically, the kernel's buffer allocation logic may attempt to read beyond the allocated memory boundaries when the returned size exceeds the actual allocated buffer size. This condition creates potential for kernel memory corruption and system crashes, particularly during migration operations where state consistency is paramount. The vulnerability affects the core virtio-pci functionality that underpins many virtualization technologies, making it a significant concern for cloud providers and virtualization platforms that rely heavily on virtio interfaces.
The mitigation implemented in this fix directly addresses the root cause by adjusting the result size calculation to properly exclude the status bytes from the data size returned to callers. This approach aligns with established best practices for buffer management and memory safety in kernel space operations. The fix specifically targets the virtqueue_get_buf() function call and ensures that the status size is properly subtracted from the total buffer length before assigning it to result_sg_size. Testing of this fix has been validated through comprehensive live migration scenarios involving virtio-net, virtio-net-transitional, and virtio-blk devices, demonstrating that the solution maintains compatibility while resolving the size calculation error. This remediation approach follows ATT&CK framework techniques related to kernel memory management and system stability, ensuring that the virtualization infrastructure maintains proper buffer boundaries during administrative command processing. The fix represents a targeted correction that preserves existing functionality while eliminating the risk of buffer overruns and memory access violations that could potentially be exploited by malicious actors in virtualized environments.