1 files changed, 26 insertions, 4 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 01ca08804f51..3f9f1d6b4c2e 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -89,16 +89,28 @@ static bool klp_is_object_loaded(struct klp_object *obj)
 /* sets obj->mod if object is not vmlinux and module is found */
 static void klp_find_object_module(struct klp_object *obj)
 {
+        struct module *mod;
+
         if (!klp_is_module(obj))
                 return;
 
         mutex_lock(&module_mutex);
         /*
-         * We don't need to take a reference on the module here because we have
-         * the klp_mutex, which is also taken by the module notifier.  This
-         * prevents any module from unloading until we release the klp_mutex.
+         * We do not want to block removal of patched modules and therefore
+         * we do not take a reference here. The patches are removed by
+         * a going module handler instead.
+         */
+        mod = find_module(obj->name);
+        /*
+         * Do not mess work of the module coming and going notifiers.
+         * Note that the patch might still be needed before the going handler
+         * is called. Module functions can be called even in the GOING state
+         * until mod->exit() finishes. This is especially important for
+         * patches that modify semantic of the functions.
          */
-        obj->mod = find_module(obj->name);
+        if (mod && mod->klp_alive)
+                obj->mod = mod;
+
         mutex_unlock(&module_mutex);
 }
 
@@ -767,6 +779,7 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
                 return -EINVAL;
 
         obj->state = KLP_DISABLED;
+        obj->mod = NULL;
 
         klp_find_object_module(obj);
 
@@ -961,6 +974,15 @@ static int klp_module_notify(struct notifier_block *nb, unsigned long action,
 
         mutex_lock(&klp_mutex);
 
+        /*
+         * Each module has to know that the notifier has been called.
+         * We never know what module will get patched by a new patch.
+         */
+        if (action == MODULE_STATE_COMING)
+                mod->klp_alive = true;
+        else /* MODULE_STATE_GOING */
+                mod->klp_alive = false;
+
         list_for_each_entry(patch, &klp_patches, list) {
                 for (obj = patch->objs; obj->funcs; obj++) {
                         if (!klp_is_module(obj) || strcmp(obj->name, mod->name))