3 files changed, 65 insertions, 2 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 88766bd..1c3c9b2 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -455,6 +455,7 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
  * /sys/kernel/livepatch/<patch>/enabled
  * /sys/kernel/livepatch/<patch>/transition
  * /sys/kernel/livepatch/<patch>/signal
+ * /sys/kernel/livepatch/<patch>/force
  * /sys/kernel/livepatch/<patch>/<object>
  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
  */
@@ -556,13 +557,42 @@ static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
 	return count;
 }
 
+static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct klp_patch *patch;
+	int ret;
+	bool val;
+
+	patch = container_of(kobj, struct klp_patch, kobj);
+
+	/*
+	 * klp_mutex lock is not grabbed here intentionally. It is not really
+	 * needed. The race window is harmless and grabbing the lock would only
+	 * hold the action back.
+	 */
+	if (patch != klp_transition_patch)
+		return -EINVAL;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	if (val)
+		klp_force_transition();
+
+	return count;
+}
+
 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
 static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
+static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
 static struct attribute *klp_patch_attrs[] = {
 	&enabled_kobj_attr.attr,
 	&transition_kobj_attr.attr,
 	&signal_kobj_attr.attr,
+	&force_kobj_attr.attr,
 	NULL
 };
 
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index edcfcb8..be5bfa5 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -33,6 +33,8 @@ struct klp_patch *klp_transition_patch;
 
 static int klp_target_state = KLP_UNDEFINED;
 
+static bool klp_forced = false;
+
 /*
  * This work can be performed periodically to finish patching or unpatching any
  * "straggler" tasks which failed to transition in the first attempt.
@@ -146,9 +148,12 @@ done:
 	/*
 	 * See complementary comment in __klp_enable_patch() for why we
 	 * keep the module reference for immediate patches.
+	 *
+	 * klp_forced or immediate_func set implies unbounded increase of
+	 * module's ref count if the module is disabled/enabled in a loop.
 	 */
-	if (!klp_transition_patch->immediate && !immediate_func &&
-	    klp_target_state == KLP_UNPATCHED) {
+	if (!klp_forced && !klp_transition_patch->immediate &&
+		!immediate_func && klp_target_state == KLP_UNPATCHED) {
 		module_put(klp_transition_patch->mod);
 	}
 
@@ -649,3 +654,30 @@ void klp_send_signals(void)
 	}
 	read_unlock(&tasklist_lock);
 }
+
+/*
+ * Drop TIF_PATCH_PENDING of all tasks on admin's request. This forces an
+ * existing transition to finish.
+ *
+ * NOTE: klp_update_patch_state(task) requires the task to be inactive or
+ * 'current'. This is not the case here and the consistency model could be
+ * broken. Administrator, who is the only one to execute the
+ * klp_force_transitions(), has to be aware of this.
+ */
+void klp_force_transition(void)
+{
+	struct task_struct *g, *task;
+	unsigned int cpu;
+
+	pr_warn("forcing remaining tasks to the patched state\n");
+
+	read_lock(&tasklist_lock);
+	for_each_process_thread(g, task)
+		klp_update_patch_state(task);
+	read_unlock(&tasklist_lock);
+
+	for_each_possible_cpu(cpu)
+		klp_update_patch_state(idle_task(cpu));
+
+	klp_forced = true;
+}
diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h
index 4052279..f9d0bc0 100644
--- a/kernel/livepatch/transition.h
+++ b/kernel/livepatch/transition.h
@@ -12,5 +12,6 @@ void klp_start_transition(void);
 void klp_try_complete_transition(void);
 void klp_reverse_transition(void);
 void klp_send_signals(void);
+void klp_force_transition(void);
 
 #endif /* _LIVEPATCH_TRANSITION_H */