Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

Pull module and param fixes from Rusty Russell:
 "Surprising number of fixes this merge window :(

  The first two are minor fallout from the param rework which went in
  this merge window.

  The next three are a series which fixes a longstanding (but never
  previously reported and unlikely , so no CC stable) race between
  kallsyms and freeing the init section.

  Finally, a minor cleanup as our module refcount will now be -1 during
  unload"

* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux:
  module: make module_refcount() a signed integer.
  module: fix race in kallsyms resolution during module load success.
  module: remove mod arg from module_free, rename module_memfree().
  module_arch_freeing_init(): new hook for archs before module->module_init freed.
  param: fix uninitialized read with CONFIG_DEBUG_LOCK_ALLOC
  param: initialize store function to NULL if not available.

1 files changed, 68 insertions, 23 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 3965511ae133..d856e96a3cce 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -772,9 +772,18 @@ static int try_stop_module(struct module *mod, int flags, int *forced)
 	return 0;
 }
 
-unsigned long module_refcount(struct module *mod)
+/**
+ * module_refcount - return the refcount or -1 if unloading
+ *
+ * @mod:	the module we're checking
+ *
+ * Returns:
+ *	-1 if the module is in the process of unloading
+ *	otherwise the number of references in the kernel to the module
+ */
+int module_refcount(struct module *mod)
 {
-	return (unsigned long)atomic_read(&mod->refcnt) - MODULE_REF_BASE;
+	return atomic_read(&mod->refcnt) - MODULE_REF_BASE;
 }
 EXPORT_SYMBOL(module_refcount);
 
@@ -856,7 +865,7 @@ static inline void print_unload_info(struct seq_file *m, struct module *mod)
 	struct module_use *use;
 	int printed_something = 0;
 
-	seq_printf(m, " %lu ", module_refcount(mod));
+	seq_printf(m, " %i ", module_refcount(mod));
 
 	/*
 	 * Always include a trailing , so userspace can differentiate
@@ -908,7 +917,7 @@ EXPORT_SYMBOL_GPL(symbol_put_addr);
 static ssize_t show_refcnt(struct module_attribute *mattr,
 			   struct module_kobject *mk, char *buffer)
 {
-	return sprintf(buffer, "%lu\n", module_refcount(mk->mod));
+	return sprintf(buffer, "%i\n", module_refcount(mk->mod));
 }
 
 static struct module_attribute modinfo_refcnt =
@@ -1795,7 +1804,7 @@ static void unset_module_core_ro_nx(struct module *mod) { }
 static void unset_module_init_ro_nx(struct module *mod) { }
 #endif
 
-void __weak module_free(struct module *mod, void *module_region)
+void __weak module_memfree(void *module_region)
 {
 	vfree(module_region);
 }
@@ -1804,6 +1813,10 @@ void __weak module_arch_cleanup(struct module *mod)
 {
 }
 
+void __weak module_arch_freeing_init(struct module *mod)
+{
+}
+
 /* Free a module, remove from lists, etc. */
 static void free_module(struct module *mod)
 {
@@ -1841,7 +1854,8 @@ static void free_module(struct module *mod)
 
 	/* This may be NULL, but that's OK */
 	unset_module_init_ro_nx(mod);
-	module_free(mod, mod->module_init);
+	module_arch_freeing_init(mod);
+	module_memfree(mod->module_init);
 	kfree(mod->args);
 	percpu_modfree(mod);
 
@@ -1850,7 +1864,7 @@ static void free_module(struct module *mod)
 
 	/* Finally, free the core (containing the module structure) */
 	unset_module_core_ro_nx(mod);
-	module_free(mod, mod->module_core);
+	module_memfree(mod->module_core);
 
 #ifdef CONFIG_MPU
 	update_protections(current->mm);
@@ -2785,7 +2799,7 @@ static int move_module(struct module *mod, struct load_info *info)
 		 */
 		kmemleak_ignore(ptr);
 		if (!ptr) {
-			module_free(mod, mod->module_core);
+			module_memfree(mod->module_core);
 			return -ENOMEM;
 		}
 		memset(ptr, 0, mod->init_size);
@@ -2930,8 +2944,9 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
 static void module_deallocate(struct module *mod, struct load_info *info)
 {
 	percpu_modfree(mod);
-	module_free(mod, mod->module_init);
-	module_free(mod, mod->module_core);
+	module_arch_freeing_init(mod);
+	module_memfree(mod->module_init);
+	module_memfree(mod->module_core);
 }
 
 int __weak module_finalize(const Elf_Ehdr *hdr,
@@ -2983,10 +2998,31 @@ static void do_mod_ctors(struct module *mod)
 #endif
 }
 
+/* For freeing module_init on success, in case kallsyms traversing */
+struct mod_initfree {
+	struct rcu_head rcu;
+	void *module_init;
+};
+
+static void do_free_init(struct rcu_head *head)
+{
+	struct mod_initfree *m = container_of(head, struct mod_initfree, rcu);
+	module_memfree(m->module_init);
+	kfree(m);
+}
+
 /* This is where the real work happens */
 static int do_init_module(struct module *mod)
 {
 	int ret = 0;
+	struct mod_initfree *freeinit;
+
+	freeinit = kmalloc(sizeof(*freeinit), GFP_KERNEL);
+	if (!freeinit) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+	freeinit->module_init = mod->module_init;
 
 	/*
 	 * We want to find out whether @mod uses async during init.  Clear
@@ -2999,18 +3035,7 @@ static int do_init_module(struct module *mod)
 	if (mod->init != NULL)
 		ret = do_one_initcall(mod->init);
 	if (ret < 0) {
-		/*
-		 * Init routine failed: abort.  Try to protect us from
-		 * buggy refcounters.
-		 */
-		mod->state = MODULE_STATE_GOING;
-		synchronize_sched();
-		module_put(mod);
-		blocking_notifier_call_chain(&module_notify_list,
-					     MODULE_STATE_GOING, mod);
-		free_module(mod);
-		wake_up_all(&module_wq);
-		return ret;
+		goto fail_free_freeinit;
 	}
 	if (ret > 0) {
 		pr_warn("%s: '%s'->init suspiciously returned %d, it should "
@@ -3055,15 +3080,35 @@ static int do_init_module(struct module *mod)
 	mod->strtab = mod->core_strtab;
 #endif
 	unset_module_init_ro_nx(mod);
-	module_free(mod, mod->module_init);
+	module_arch_freeing_init(mod);
 	mod->module_init = NULL;
 	mod->init_size = 0;
 	mod->init_ro_size = 0;
 	mod->init_text_size = 0;
+	/*
+	 * We want to free module_init, but be aware that kallsyms may be
+	 * walking this with preempt disabled.  In all the failure paths,
+	 * we call synchronize_rcu/synchronize_sched, but we don't want
+	 * to slow down the success path, so use actual RCU here.
+	 */
+	call_rcu(&freeinit->rcu, do_free_init);
 	mutex_unlock(&module_mutex);
 	wake_up_all(&module_wq);
 
 	return 0;
+
+fail_free_freeinit:
+	kfree(freeinit);
+fail:
+	/* Try to protect us from buggy refcounters. */
+	mod->state = MODULE_STATE_GOING;
+	synchronize_sched();
+	module_put(mod);
+	blocking_notifier_call_chain(&module_notify_list,
+				     MODULE_STATE_GOING, mod);
+	free_module(mod);
+	wake_up_all(&module_wq);
+	return ret;
 }
 
 static int may_init_module(void)