Re: [RESEND][PATCH v3 03/17] module: Properly propagate MODULE_STATE_COMING failure

+++ Peter Zijlstra [24/03/20 14:56 +0100]:

quoted

Now that notifiers got unbroken; use the proper interface to handle
notifier errors and propagate them.

There were already MODULE_STATE_COMING notifiers that failed; notably:

- jump_label_module_notifier()
- tracepoint_module_notify()
- bpf_event_notify()

By propagating this error, we fix those users.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: jeyu@kernel.org
---
kernel/module.c |   10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/kernel/module.c
+++ b/kernel/module.c

@@ -3751,9 +3751,13 @@ static int prepare_coming_module(struct

	if (err)
		return err;

-	blocking_notifier_call_chain(&module_notify_list,
-				     MODULE_STATE_COMING, mod);
-	return 0;
+	err = blocking_notifier_call_chain_robust(&module_notify_list,
+			MODULE_STATE_COMING, MODULE_STATE_GOING, mod);
+	err = notifier_to_errno(err);
+	if (err)
+		klp_module_going(mod);
+
+	return err;
}

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

This looks fine to me - klp_module_going() is only called after
successful klp_module_coming(), and klp_module_going() is fine with
mod->state still being MODULE_STATE_COMING here. Would be good to have
livepatch folks double check. Which reminds me - Miroslav had pointed
out in the past that if there is an error when calling the COMING
notifiers, the GOING notifiers will be called while the mod->state is
still MODULE_STATE_COMING. I've briefly looked through all the module
notifiers and it looks like nobody is looking at mod->state directly
at least.

Acked-by: Jessica Yu <jeyu@kernel.org>