Affected: Linux

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

HID: sony: fix UAF of ghl_poke_timer / ghl_urb at driver unbind

For GHL (Guitar Hero Live) dongles, sony_probe() arms a periodic timer: ghl_magic_poke() (the timer callback) submits sc->ghl_urb, and the URB completion ghl_magic_poke_cb() re-arms the timer with mod_timer().

sony_remove() drained the timer with timer_delete_sync() and then freed the URB with usb_free_urb():

timer_delete_sync(&sc->ghl_poke_timer); usb_free_urb(sc->ghl_urb);

timer_delete_sync() does not block re-arming, and while the URB is in flight the timer is not pending, so the sync delete is a no-op. A URB completion that runs after the delete re-arms the timer, and usb_free_urb() only drops a reference -- it does not kill an in-flight URB. sc is allocated with devm_kzalloc() and freed once sony_remove() returns, so the re-armed ghl_poke_timer (embedded in sc) then fires on freed memory, a use-after-free from timer softirq. This is a disconnect/rmmod race.

Poison the URB first, then shut the timer down, before freeing the URB. usb_poison_urb() kills any in-flight URB and permanently rejects further submissions, so a poke timer that is still pending cannot re-submit the URB from ghl_magic_poke() in the window before timer_shutdown_sync() runs. usb_kill_urb() would not suffice: it only cancels the in-flight URB and leaves it submittable once it returns, so the pending timer could re-submit it and put a fresh URB in flight over the fr…