Linux Kernel EUVD-2026-28730

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

usb: gadget: f_tcm: Fix NULL pointer dereferences in nexus handling

The tpg->tpg_nexus pointer in the USB Target driver is dynamically managed and tied to userspace configuration via ConfigFS. It can be NULL if the USB host sends requests before the nexus is fully established or immediately after it is dropped.

Currently, functions like bot_submit_command() and the data transfer paths retrieve tv_nexus = tpg->tpg_nexus and immediately dereference tv_nexus->tvn_se_sess without any validation. If a malicious or misconfigured USB host sends a BOT (Bulk-Only Transport) command during this race window, it triggers a NULL pointer dereference, leading to a kernel panic (local DoS).

This exposes an inconsistent API usage within the module, as peer functions like usbg_submit_command() and bot_send_bad_response() correctly implement a NULL check for tv_nexus before proceeding.

Fix this by bringing consistency to the nexus handling. Add the missing if (!tv_nexus) checks to the vulnerable BOT command and request processing paths, aborting the command gracefully with an error instead of crashing the system.