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

Greg KH
2024-05-04T16:53:09Z

On Wed, Apr 24, 2024 at 08:09:05PM +0800, Yafang Shao wrote:
> On Sun, Apr 7, 2024 at 11:58 AM Yafang Shao <laoar.shao@gmail.com> wrote:
> >
> > 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
> >
>
> Luis, Greg,
>
> Since the last version, there hasn't been any response. Would you mind
> taking a moment to review it and provide your feedback on the
> kernel/module changes?

There was response on patch 2/2, which is why I deleted this from my
review queue a long time ago.

Please address that if you wish to, and then resend if you feel this is
still needed.

Personally, I really don't like this function you added...

thanks,

greg k-h