Type confusion in the device_deinit system call allows user-mode threads to execute arbitrary kernel code

The user-mode verification handler for the device_deinit() system call, z_vrfy_device_deinit() in kernel/device.c, validated its dev argument with K_SYSCALL_OBJ_INIT(dev, K_OBJ_ANY). k_object_validate() short-circuits its type comparison when the requested type is K_OBJ_ANY, so the check reduced to "this pointer is the base address of some kernel object the calling thread has been granted" — the object's actual type was never compared, and K_SYSCALL_OBJ_INIT also skips the initialization-state check. The sibling handlers z_vrfy_device_init() and z_vrfy_device_is_ready() already used K_OBJ_DRIVER_ANY and were unaffected. A thread running in user mode can therefore pass any kernel object it holds permission on — most usefully a thread stack object obtained from the k_thread_stack_alloc() syscall or a statically defined K_THREAD_STACK it was granted in order to spawn a child user thread — whose backing memory is writable from user mode. z_impl_device_deinit() then interprets those attacker-written bytes as a struct device: it dereferences the state pointer read out of the object, calls the function pointer read out of ops.deinit, and on success writes through state again. The result is an indirect call to an arbitrary address executed in supervisor mode, plus an arbitrary kernel read and a single-byte kernel write. Exploitation gives a local unprivileged thread full kernel code execution, defeating the CONFIG_USERSPACE isolation boundary entirely; a less precise attempt yields a