gpio: mpsse: fix race when arming the IRQ poll worker

Overview

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

gpio: mpsse: fix race when arming the IRQ poll worker

gpio_mpsse_irq_enable() arms the poll worker before publishing it: schedule_work() runs before the worker is added to priv->workers. If gpio_mpsse_disconnect() walks the list in that window it misses the worker, and once disconnect returns, the USB core frees mpsse_priv while the orphaned gpio_mpsse_poll() work keeps accessing it, causing a use-after-free.

Fix this by publishing and arming the worker in one irq_spin critical section. Teardown walks the same list under irq_spin, so a worker found on the list is guaranteed to be armed, and cancel_work_sync() handles it whether it is queued or running.

A worker armed after the disconnect walk would still be missed, so also set a new priv->dying flag under irq_spin before the teardown walk, and check it in the same critical section, freeing it via kfree_rcu() instead when the device is going away, since kfree() would be called with the IRQ core's raw spinlock held and may sleep on PREEMPT_RT. schedule_work() is safe to call with irq_spin held, and the next probe gets a fresh mpsse_priv, so the flag never needs to be cleared.

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

Affected

• Linux >= 472d900c8bcac301ae0e40fdca7db799bd989ff5 < 76390ac0bca7e5058b7482eb4d951c3bda5df812
• Linux >= 179ef1127d7a4f09f0e741fa9f30b8a8e7886271 < c0071ee496e1228976c72b096f529503222708a0
• Linux >= 179ef1127d7a4f09f0e741fa9f30b8a8e7886271 < 7efa1a1953cd6b20b23a3524d5b4b81789c6ef25
• Linux >= 6.18.6 < 6.18.57
• Linux 6.19

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.