3 files changed, 65 insertions, 2 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 88766bd91803..1c3c9b27c916 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 edcfcb8ebb2d..be5bfa533ee8 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 40522795a5f6..f9d0bc016067 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 */