Overview
About vulnerability
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.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
- Affected packages:
- kernel @ 4.18.0 (+13 more)
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.