CVE-2025-40004

In the Linux kernel, the following vulnerability has been resolved:

net/9p: Fix buffer overflow in USB transport layer

A buffer overflow vulnerability exists in the USB 9pfs transport layer

where inconsistent size validation between packet header parsing and

actual data copying allows a malicious USB host to overflow heap buffers.

The issue occurs because:

- usb9pfs_rx_header() validates only the declared size in packet header

- usb9pfs_rx_complete() uses req->actual (actual received bytes) for

memcpy

This allows an attacker to craft packets with small declared size

(bypassing validation) but large actual payload (triggering overflow

in memcpy).

Add validation in usb9pfs_rx_complete() to ensure req->actual does not

exceed the buffer capacity before copying data.