CyberRota Analysis
AI-GeneratedThe vulnerability affects the Linux kernel's USB gadget subsystem, specifically in the handling of port counts during LUN (Logical Unit Number) teardown processes. An attacker could exploit a race condition between LUN removal and nexus removal, potentially leading to use-after-free conditions that could crash the system or allow unauthorized access to memory. Organizations using Linux kernel versions that include this subsystem should prioritize patching to mitigate the risk of system instability and potential exploitation.
Original NVD 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 nonzero until core_dev_del_lun() has finished draining active LUN references, preventing nexus removal from freeing the session during command completion.