CVE-2026-64328usb: gadget: f_fs: Fix DMA fence leak

Official 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b7475b2dce5e121e687280ba5732ccefe77ffd2f
• https://git.kernel.org/stable/c/e086c16962a1b0142e2675610e9c06fcfcd4c3a8
• https://git.kernel.org/stable/c/0cae3d6109427c455bad0a18dfb3e2a91657e38a
• https://git.kernel.org/stable/c/baa6b6068a3f2bf2ed525a1cb37975905dadc658