On Fri, 14 Jan 2022, Jann Horn wrote:
uhid has to run hid_add_device() from workqueue context while allowing parallel use of the userspace API (which is protected with ->devlock). But hid_add_device() can fail. Currently, that is handled by immediately destroying the associated HID device, without using ->devlock - but if there are concurrent requests from userspace, that's wrong and leads to NULL dereferences and/or memory corruption (via use-after-free).
Fix it by leaving the HID device as-is in the worker. We can clean it up later, either in the UHID_DESTROY command handler or in the ->release() handler.
Cc: stable@vger.kernel.org Fixes: 67f8ecc550b5 ("HID: uhid: fix timeout when probe races with IO") Signed-off-by: Jann Horn jannh@google.com
I've queued both patches for 5.17, thanks a lot for fixing this.