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

Yafang Shao
2024-04-07T03:58:03Z

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