[PATCH v2 1/2] module: Add a new helper delete_module()

[Yafang Shao <laoar.shao@gmail.com>]

Introduce a new helper function, delete_module(), designed to delete kernel
modules from locations outside of the `kernel/module` directory.

No functional change.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/module.h |  1 +
 kernel/module/main.c   | 82 ++++++++++++++++++++++++++++++++----------
 2 files changed, 65 insertions(+), 18 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 1153b0d99a80..c24557f1b795 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -75,6 +75,7 @@ extern struct module_attribute module_uevent;
 /* These are either module local, or the kernel's dummy ones. */
 extern int init_module(void);
 extern void cleanup_module(void);
+extern int delete_module(struct module *mod);
 
 #ifndef MODULE
 /**
diff --git a/kernel/module/main.c b/kernel/module/main.c
index e1e8a7a9d6c1..3b48ee66db41 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -695,12 +695,74 @@ EXPORT_SYMBOL(module_refcount);
 /* This exists whether we can unload or not */
 static void free_module(struct module *mod);
 
+static void __delete_module(struct module *mod)
+{
+	char buf[MODULE_FLAGS_BUF_SIZE];
+
+	WARN_ON_ONCE(mod->state != MODULE_STATE_GOING);
+
+	/* Final destruction now no one is using it. */
+	if (mod->exit != NULL)
+		mod->exit();
+	blocking_notifier_call_chain(&module_notify_list,
+				     MODULE_STATE_GOING, mod);
+	klp_module_going(mod);
+	ftrace_release_mod(mod);
+
+	async_synchronize_full();
+
+	/* Store the name and taints of the last unloaded module for diagnostic purposes */
+	strscpy(last_unloaded_module.name, mod->name, sizeof(last_unloaded_module.name));
+	strscpy(last_unloaded_module.taints, module_flags(mod, buf, false),
+		sizeof(last_unloaded_module.taints));
+
+	free_module(mod);
+	/* someone could wait for the module in add_unformed_module() */
+	wake_up_all(&module_wq);
+}
+
+int delete_module(struct module *mod)
+{
+	int ret;
+
+	mutex_lock(&module_mutex);
+	if (!list_empty(&mod->source_list)) {
+		/* Other modules depend on us: get rid of them first. */
+		ret = -EWOULDBLOCK;
+		goto out;
+	}
+
+	/* Doing init or already dying? */
+	if (mod->state != MODULE_STATE_LIVE) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/* If it has an init func, it must have an exit func to unload */
+	if (mod->init && !mod->exit) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (try_release_module_ref(mod) != 0) {
+		ret = -EWOULDBLOCK;
+		goto out;
+	}
+	mod->state = MODULE_STATE_GOING;
+	mutex_unlock(&module_mutex);
+	__delete_module(mod);
+	return 0;
+
+out:
+	mutex_unlock(&module_mutex);
+	return ret;
+}
+
 SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
 		unsigned int, flags)
 {
 	struct module *mod;
 	char name[MODULE_NAME_LEN];
-	char buf[MODULE_FLAGS_BUF_SIZE];
 	int ret, forced = 0;
 
 	if (!capable(CAP_SYS_MODULE) || modules_disabled)
@@ -750,23 +812,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
 		goto out;
 
 	mutex_unlock(&module_mutex);
-	/* Final destruction now no one is using it. */
-	if (mod->exit != NULL)
-		mod->exit();
-	blocking_notifier_call_chain(&module_notify_list,
-				     MODULE_STATE_GOING, mod);
-	klp_module_going(mod);
-	ftrace_release_mod(mod);
-
-	async_synchronize_full();
-
-	/* Store the name and taints of the last unloaded module for diagnostic purposes */
-	strscpy(last_unloaded_module.name, mod->name, sizeof(last_unloaded_module.name));
-	strscpy(last_unloaded_module.taints, module_flags(mod, buf, false), sizeof(last_unloaded_module.taints));
-
-	free_module(mod);
-	/* someone could wait for the module in add_unformed_module() */
-	wake_up_all(&module_wq);
+	__delete_module(mod);
 	return 0;
 out:
 	mutex_unlock(&module_mutex);
-- 
2.39.1