CVE-2026-80854

/// Technical description

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

usb: gadget: f_tcm: keep port count until LUN teardown completes

tcm_usbg_drop_nexus() permits session removal once tpg_port_count

reaches zero. However, usbg_port_unlink() currently decrements that

count from the fabric_pre_unlink() callback, before core_dev_del_lun()

waits for active se_lun references to drain.

If removal of the last LUN races a nexus removal, the latter can observe

a zero port count and call target_remove_session(). This frees

sess_cmd_map while an in-flight struct usbg_cmd, including its work item,

can still be accessed.

Overlapping the last-LUN unlink with nexus removal reproduces this

lifetime violation as a DEBUG_OBJECTS "free active" warning for

usbg_cmd_work, followed by a target-core BUG/Oops.

The generic target-core unlink path has no callback after

core_dev_del_lun() completes. Add an optional fabric_post_unlink()

callback and use it for the f_tcm port count. The count now remains

nonz

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References