Re: [POC 2/7] livepatch: Allow to handle lifetime of shadow variables using the livepatch state

From: Petr Mladek
Date: Thu Aug 15 2024 - 09:44:01 EST


On Thu 2024-07-25 13:31:40, Miroslav Benes wrote:
> > diff --git a/kernel/livepatch/state.c b/kernel/livepatch/state.c
> > index 6693d808106b..4ec65afe3a43 100644
> > --- a/kernel/livepatch/state.c
> > +++ b/kernel/livepatch/state.c
> > @@ -198,11 +198,17 @@ void klp_release_states(struct klp_patch *patch)
> > if (is_state_in_other_patches(patch, state))
> > continue;
> >
> > - if (!state->callbacks.release)
> > - continue;
> > -
> > - if (state->callbacks.setup_succeeded)
> > + if (state->callbacks.release && state->callbacks.setup_succeeded)
> > state->callbacks.release(patch, state);
> > +
> > + if (state->is_shadow)
> > + klp_shadow_free_all(state->id, state->callbacks.shadow_dtor);
>
> The following
>
> > + /*
> > + * The @release callback is supposed to restore the original
> > + * state before the @setup callback was called.
> > + */
> > + state->callbacks.setup_succeeded = 0;
>
> should go to the previous patch perhaps?

Great catch!

I am going to refactor the code in the next version so that it would
look like:

void klp_states_post_unpatch(struct klp_patch *patch)
{
struct klp_state *state;

klp_for_each_state(patch, state) {
if (is_state_in_other_patches(patch, state))
continue;

if (!state->callbacks.pre_patch_succeeded)
continue;

if (state->callbacks.post_unpatch)
state->callbacks.post_unpatch(patch, state);

+ if (state->is_shadow)
+ klp_shadow_free_all(state->id, state->callbacks.shadow_dtor);
+
state->callbacks.pre_patch_succeeded = 0;
}
}


Best Regards,
Petr