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SubjectRe: [RFC][PATCH] module: Propagate MODULE_STATE_COMING notifier errors
On Wed, Jun 19, 2019 at 01:23:50PM +0200, Peter Zijlstra wrote:
> On Wed, Jun 19, 2019 at 01:12:12PM +0200, Miroslav Benes wrote:
> > > @@ -3780,7 +3781,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
> > >
> > > err = prepare_coming_module(mod);
> > > if (err)
> > > - goto bug_cleanup;
> > > + goto coming_cleanup;
> >
> > Not good. klp_module_going() is not prepared to be called without
> > klp_module_coming() succeeding. "Funny" things might happen.
>
> Bah, I did look at that but failed to spot it :/
>
> > So it calls for more fine-grained error handling.
>
> Another approach that I considered was trying to re-iterate the notifier
> list up until the point we got, but that was fairly non-trivial and
> needed changes to the notifier crud itself.
>
> I'll try again.

How's something like so:

diff --git a/kernel/module.c b/kernel/module.c
index 80c7c09584cf..eba6560c89da 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3631,16 +3631,28 @@ static int complete_formation(struct module *mod, struct load_info *info)

static int prepare_coming_module(struct module *mod)
{
- int err;
+ struct blocking_notifier_head *nh = &module_notify_list;
+ int err, nr;

ftrace_module_enable(mod);
err = klp_module_coming(mod);
if (err)
return err;

- blocking_notifier_call_chain(&module_notify_list,
- MODULE_STATE_COMING, mod);
- return 0;
+ if (!rcu_access_pointer(nh->head))
+ return 0;
+
+ down_read(&nh->rwsem);
+ ret = notifier_call_chain(&nh->head, MODULE_STATE_COMING, mod, -1, &nr);
+ if (ret & NOTIFIER_STOP_MASK)
+ notifier_call_chain(&nh->head, MODULE_STATE_GOING, mod, nr, NULL);
+ up_read(&nh->rwsem);
+
+ err = notifier_to_err(err);
+ if (err)
+ klp_module_going(mod);
+
+ return err;
}

static int unknown_module_param_cb(char *param, char *val, const char *modname,
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