CVE-2026-64328
Received Received - Intake

Memory Leak in Linux Kernel USB Gadget

Publication date: 2026-07-25

Last updated on: 2026-07-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Fix DMA fence leak In ffs_dmabuf_transfer(), a ffs_dma_fence object is kmalloc'd, with the underlying dma_fence later initialized by dma_fence_init(), which sets its kref counter to 1. Then, dma_resv_add_fence() gets a second reference, and a pointer to the ffs_dma_fence is passed as the usb_request's "context" field. The dma-resv mechanism will manage the second reference, but the first reference is never properly released; the ffs_dmabuf_cleanup() function decreases the reference count, but only to balance with the reference grab in ffs_dmabuf_signal_done(). The code will then slowly leak memory as more ffs_dma_fence objects are created without being ever freed. Address this issue by transferring ownership of the fence to the DMA reservation object, by calling dma_fence_put() right after dma_resv_add_fence(). The ffs_dma_fence then gets properly discarded after being signalled.

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Meta Information

Published
2026-07-25
Last Modified
2026-07-25
Generated
2026-07-25
AI Q&A
2026-07-25
EPSS Evaluated
N/A
NVD
CVE-2026-64328
EUVD
EUVD-2026-48872

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a memory leak in the USB gadget function filesystem (f_fs). When handling DMA operations, a ffs_dma_fence object is allocated but not properly freed. The first reference to the fence is never released, causing memory to leak as more objects are created without cleanup.

Detection Guidance

This vulnerability is specific to the Linux kernel's USB gadget filesystem (f_fs) and involves a DMA fence leak. Detection requires checking kernel logs for related errors or monitoring memory usage for gradual leaks in USB gadget subsystems. Commands like 'dmesg | grep -i fence' or 'journalctl -k | grep -i fence' may help identify issues. Regularly monitor system memory with tools like 'top' or 'htop' for unusual patterns.

Impact Analysis

This vulnerability can lead to gradual memory exhaustion on systems using the affected USB gadget functionality. Over time, the system may run out of memory, causing performance degradation or crashes in applications relying on USB device operations.

Mitigation Strategies

Update your Linux kernel to a patched version that includes the fix for this vulnerability. If immediate patching is not possible, consider disabling USB gadget functionality if not required. Monitor system logs for DMA fence-related errors and ensure DMA operations are properly managed.

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