CVE-2026-89738

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

usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed

In polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a

self-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and

at91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via

mod_timer(). Both recover the same udc through container_of and dereference

it on every iteration.

Neither teardown path cancels this cycle. udc is devm-allocated, so it is

freed after at91udc_remove() returns, and is likewise freed when probe

fails and devres runs. A timer callback or work item that is pending or

running at either point dereferences the freed udc.

Add at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and

from the usb_add_gadget_udc() failure path in probe; the remaining probe

error paths fail before the timer is armed. timer_shutdown_sync() waits

for a running callback and clears timer->function, which makes the work

handler's mod_timer() a permanent no-op; cancel_work_sync() then drains

any pending or running work whose re-arm attempt now does nothing. The

timer must be shut down first, since cancelling the work alone would let

the timer re-queue it. The guard mirrors probe: in IRQ mode the timer and

work_struct are never initialized.

This does not require a fault; a normal driver unbind can interleave with

an already queued work item.

This issue was found by an in-house static analysis tool.