sched: enforce ref-counting on current task/thread pointers

arch/x86_64/thread.c

@@ -95,25 +95,30 @@ kern_status_t ml_thread_config_set(
 	const void *ptr,
 	size_t len)
 {
+	struct thread *self = get_current_thread();
+	kern_status_t status = KERN_OK;
+
 	switch (key) {
 	case THREAD_CFG_FSBASE:
 		if (len != sizeof(thread->tr_ml.tr_fsbase)) {
-			return KERN_INVALID_ARGUMENT;
+			status = KERN_INVALID_ARGUMENT;
+			break;
 		}
 
 		thread->tr_ml.tr_fsbase = *(virt_addr_t *)ptr;
-		if (thread == current_thread()) {
+		if (thread == self) {
 			wrmsr(MSR_FS_BASE, thread->tr_ml.tr_fsbase);
 		}
 
 		break;
 	case THREAD_CFG_GSBASE:
 		if (len != sizeof(thread->tr_ml.tr_gsbase)) {
-			return KERN_INVALID_ARGUMENT;
+			status = KERN_INVALID_ARGUMENT;
+			break;
 		}
 
 		thread->tr_ml.tr_gsbase = *(virt_addr_t *)ptr;
-		if (thread == current_thread()) {
+		if (thread == self) {
 			/* we're in the kernel right now, so the user and kernel
 			 * gs-base registers are swapped. when we return to
 			 * usermode, this value will be swapped back into
@@ -123,8 +128,10 @@ kern_status_t ml_thread_config_set(
 
 		break;
 	default:
-		return KERN_INVALID_ARGUMENT;
+		status = KERN_INVALID_ARGUMENT;
+		break;
 	}
 
-	return KERN_OK;
+	put_current_thread(self);
+	return status;
 }