It seems that you try to remove the disabled module by the kip replace. However, changing the code of sys call may introduce some unnecessary changes to non-livepatch module. Is that really a safe way to do so?
> On Mar 31, 2024, at 21:38, Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> Enhance the functionality of kpatch to automatically remove the associated
> module when replacing an old livepatch with a new one. This ensures that no
> leftover modules remain in the system. For instance:
>
> - Load the first livepatch
> $ kpatch load 6.9.0-rc1+/livepatch-test_0.ko
> loading patch module: 6.9.0-rc1+/livepatch-test_0.ko
> waiting (up to 15 seconds) for patch transition to complete...
> transition complete (2 seconds)
>
> $ kpatch list
> Loaded patch modules:
> livepatch_test_0 [enabled]
>
> $ lsmod |grep livepatch
> livepatch_test_0 16384 1
>
> - Load a new livepatch
> $ kpatch load 6.9.0-rc1+/livepatch-test_1.ko
> loading patch module: 6.9.0-rc1+/livepatch-test_1.ko
> waiting (up to 15 seconds) for patch transition to complete...
> transition complete (2 seconds)
>
> $ kpatch list
> Loaded patch modules:
> livepatch_test_1 [enabled]
>
> $ lsmod |grep livepatch
> livepatch_test_1 16384 1
> livepatch_test_0 16384 0 <<<< leftover
>
> With this improvement, executing
> `kpatch load 6.9.0-rc1+/livepatch-test_1.ko` will automatically remove the
> livepatch-test_0.ko module.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> include/linux/module.h | 1 +
> kernel/livepatch/core.c | 11 +++++++++--
> kernel/module/main.c | 43 ++++++++++++++++++++++++-----------------
> 3 files changed, 35 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 1153b0d99a80..9a95174a919b 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 void delete_module(struct module *mod);
>
> #ifndef MODULE
> /**
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index ecbc9b6aba3a..f1edc999f3ef 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -711,6 +711,8 @@ static void klp_free_patch_start(struct klp_patch *patch)
> */
> static void klp_free_patch_finish(struct klp_patch *patch)
> {
> + struct module *mod = patch->mod;
> +
> /*
> * Avoid deadlock with enabled_store() sysfs callback by
> * calling this outside klp_mutex. It is safe because
> @@ -721,8 +723,13 @@ static void klp_free_patch_finish(struct klp_patch *patch)
> wait_for_completion(&patch->finish);
>
> /* Put the module after the last access to struct klp_patch. */
> - if (!patch->forced)
> - module_put(patch->mod);
> + if (!patch->forced) {
> + module_put(mod);
> + if (module_refcount(mod))
> + return;
> + mod->state = MODULE_STATE_GOING;
> + delete_module(mod);
> + }
> }
>
> /*
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index e1e8a7a9d6c1..e863e1f87dfd 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -695,12 +695,35 @@ EXPORT_SYMBOL(module_refcount);
> /* This exists whether we can unload or not */
> static void free_module(struct module *mod);
>
> +void delete_module(struct module *mod)
> +{
> + char buf[MODULE_FLAGS_BUF_SIZE];
> +
> + /* 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);
> +}
> +
> 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 +773,7 @@ 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
>
>
