On Fri, Jan 29, 2016 at 03:04:51PM -0500, Jessica Yu wrote:
> +++ Josh Poimboeuf [29/01/16 11:30 -0600]:
> >On Fri, Jan 29, 2016 at 05:30:46PM +0100, Miroslav Benes wrote:
> >>Otherwise than that it looks good. I agree there are advantages to split
> >>the notifiers. For example we can replace the coming one with the function
> >>call somewhere in load_module() to improve error handling if the patching
> >>fails while loading a module. This would be handy with a consistency model
> >>in the future.
> >
> >Yeah, we'll need something like that eventually. Though we'll need to
> >make sure that ftrace_module_enable() is still called beforehand, after
> >setting MODULE_STATE_COMING state, due to the race described in 5156dca.
> >
> >Something like:
> >
> >[note: klp_module_notify_coming() is replaced with klp_module_enable()]
> >
> >diff --git a/kernel/module.c b/kernel/module.c
> >index 8358f46..aeabd81 100644
> >--- a/kernel/module.c
> >+++ b/kernel/module.c
> >@@ -3371,6 +3371,13 @@ static int complete_formation(struct module *mod, struct load_info *info)
> > mod->state = MODULE_STATE_COMING;
> > mutex_unlock(&module_mutex);
> >
> >+ ftrace_module_enable(mod);
> >+ err = klp_module_enable(mod);
> >+ if (err) {
> >+ ftrace_release_mod(mod);
> >+ return err;
> >+ }
>
> If we go this route, should we should print a big warning ("Livepatch
> couldn't patch loading module X") instead of aborting the module load
> completely?
I think aborting the module load is better. Otherwise the patch would
be applied in an inconsistent state. Which might not be all that bad
now, since we don't have a consistency model anyway; but it could be
disastrous once we get one, if somebody is relying on that consistency.
--
Josh
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