usb: gadget: udc: fix use-after-free in usb_gadget_state_work

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: udc: fix use-after-free in usb_gadget_state_work A race condition during gadget teardown can lead to a use-after-free in usb_gadget_state_work(), as reported by KASAN: BUG: KASAN: invalid-access in sysfs_notify+0x2c/0xd0 Workqueue: events usb_gadget_state_work The fundamental race occurs because a concurrent event (e.g., an interrupt) can call usb_gadget_set_state() and schedule gadget->work at any time during the cleanup process in usb_del_gadget(). Commit 399a45e5237c ("usb: gadget: core: flush gadget workqueue after device removal") attempted to fix this by moving flush_work() to after device_del(). However, this does not fully solve the race, as a new work item can still be scheduled *after* flush_work() completes but before the gadget's memory is freed, leading to the same use-after-free. This patch fixes the race condition robustly by introducing a 'teardown' flag and a 'state_lock' spinlock to the usb_gadget struct. The flag is set during cleanup in usb_del_gadget() *before* calling flush_work() to prevent any new work from being scheduled once cleanup has commenced. The scheduling site, usb_gadget_set_state(), now checks this flag under the lock before queueing the work, thus safely closing the race window.

References

• https://git.kernel.org/stable/c/dddc944d65169b552e09cb54e3ed4fbb9ea26416
• https://git.kernel.org/stable/c/eee16f3ff08e759ea828bdf7dc1c0ef2f22134f5
• https://git.kernel.org/stable/c/c12a0c3ef815ddd67e47f9c819f9fe822fed5467
• https://git.kernel.org/stable/c/f02a412c0a18f02f0f91b0a3d9788315a721b7fd
• https://git.kernel.org/stable/c/10014310193cf6736c1aeb4105c5f4a0818d0c65
• https://git.kernel.org/stable/c/3b32caa73d135eea8fb9cabb45e9fc64c5a3ecb9
• https://git.kernel.org/stable/c/baeb66fbd4201d1c4325074e78b1f557dff89b5b