1 files changed, 75 insertions, 41 deletions

diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 56add6327736..7c6631e693bc 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.
@@ -80,7 +82,6 @@ static void klp_complete_transition(void)
 	struct klp_func *func;
 	struct task_struct *g, *task;
 	unsigned int cpu;
-	bool immediate_func = false;
 
 	pr_debug("'%s': completing %s transition\n",
 		 klp_transition_patch->mod->name,
@@ -102,16 +103,9 @@ static void klp_complete_transition(void)
 		klp_synchronize_transition();
 	}
 
-	if (klp_transition_patch->immediate)
-		goto done;
-
-	klp_for_each_object(klp_transition_patch, obj) {
-		klp_for_each_func(obj, func) {
+	klp_for_each_object(klp_transition_patch, obj)
+		klp_for_each_func(obj, func)
 			func->transition = false;
-			if (func->immediate)
-				immediate_func = true;
-		}
-	}
 
 	/* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */
 	if (klp_target_state == KLP_PATCHED)
@@ -130,7 +124,6 @@ static void klp_complete_transition(void)
 		task->patch_state = KLP_UNDEFINED;
 	}
 
-done:
 	klp_for_each_object(klp_transition_patch, obj) {
 		if (!klp_is_object_loaded(obj))
 			continue;
@@ -144,13 +137,11 @@ done:
 		  klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
 
 	/*
-	 * See complementary comment in __klp_enable_patch() for why we
-	 * keep the module reference for immediate patches.
+	 * klp_forced 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_target_state == KLP_UNPATCHED)
 		module_put(klp_transition_patch->mod);
-	}
 
 	klp_target_state = KLP_UNDEFINED;
 	klp_transition_patch = NULL;
@@ -218,9 +209,6 @@ static int klp_check_stack_func(struct klp_func *func,
 	struct klp_ops *ops;
 	int i;
 
-	if (func->immediate)
-		return 0;
-
 	for (i = 0; i < trace->nr_entries; i++) {
 		address = trace->entries[i];
 
@@ -383,13 +371,6 @@ void klp_try_complete_transition(void)
 	WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED);
 
 	/*
-	 * If the patch can be applied or reverted immediately, skip the
-	 * per-task transitions.
-	 */
-	if (klp_transition_patch->immediate)
-		goto success;
-
-	/*
 	 * Try to switch the tasks to the target patch state by walking their
 	 * stacks and looking for any to-be-patched or to-be-unpatched
 	 * functions.  If such functions are found on a stack, or if the stack
@@ -432,7 +413,6 @@ void klp_try_complete_transition(void)
 		return;
 	}
 
-success:
 	/* we're done, now cleanup the data structures */
 	klp_complete_transition();
 }
@@ -453,13 +433,6 @@ void klp_start_transition(void)
 		  klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
 
 	/*
-	 * If the patch can be applied or reverted immediately, skip the
-	 * per-task transitions.
-	 */
-	if (klp_transition_patch->immediate)
-		return;
-
-	/*
 	 * Mark all normal tasks as needing a patch state update.  They'll
 	 * switch either in klp_try_complete_transition() or as they exit the
 	 * kernel.
@@ -509,13 +482,6 @@ void klp_init_transition(struct klp_patch *patch, int state)
 		 klp_target_state == KLP_PATCHED ? "patching" : "unpatching");
 
 	/*
-	 * If the patch can be applied or reverted immediately, skip the
-	 * per-task transitions.
-	 */
-	if (patch->immediate)
-		return;
-
-	/*
 	 * Initialize all tasks to the initial patch state to prepare them for
 	 * switching to the target state.
 	 */
@@ -608,3 +574,71 @@ void klp_copy_process(struct task_struct *child)
 
 	/* TIF_PATCH_PENDING gets copied in setup_thread_stack() */
 }
+
+/*
+ * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.
+ * Kthreads with TIF_PATCH_PENDING set are woken up. Only admin can request this
+ * action currently.
+ */
+void klp_send_signals(void)
+{
+	struct task_struct *g, *task;
+
+	pr_notice("signaling remaining tasks\n");
+
+	read_lock(&tasklist_lock);
+	for_each_process_thread(g, task) {
+		if (!klp_patch_pending(task))
+			continue;
+
+		/*
+		 * There is a small race here. We could see TIF_PATCH_PENDING
+		 * set and decide to wake up a kthread or send a fake signal.
+		 * Meanwhile the task could migrate itself and the action
+		 * would be meaningless. It is not serious though.
+		 */
+		if (task->flags & PF_KTHREAD) {
+			/*
+			 * Wake up a kthread which sleeps interruptedly and
+			 * still has not been migrated.
+			 */
+			wake_up_state(task, TASK_INTERRUPTIBLE);
+		} else {
+			/*
+			 * Send fake signal to all non-kthread tasks which are
+			 * still not migrated.
+			 */
+			spin_lock_irq(&task->sighand->siglock);
+			signal_wake_up(task, 0);
+			spin_unlock_irq(&task->sighand->siglock);
+		}
+	}
+	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;
+}