[Letux-kernel] BUG: drivers/pinctrl/core: races in pinctrl_groups and deferred probing

[Tony Lindgren]

* H. Nikolaus Schaller <hns at goldelico.com> [180618 16:46]:

> 
> I can also demonstrate that the duplication has gone:

OK good to hear.

> And I was no longer able to reproduce the strcmp(NULL) issue. So it is either better hidden
> or gone.

It should not be possible with checks preventing registering
a group or function with no name. I'll try to repost the whole
series tomorrow with that added.

> So code just needs group cleanup on failed probing and fixing the mutex around pinctrl_generic_add_group().
> 
> I think we need the mutex because a race still can happen when create_pinctrl() is calling pcs_dt_node_to_map()
> and pinctrl_generic_add_group() w/o being locked on pinctrl_maps_mutex.
> 
> The race I suspect is that two drivers are trying to insert the same name and may come
> both to the conclusion that it does not yet exist. And both insert into the radix tree.
> 
> The window of risk is small though... It is in pinctrl_generic_add_group() between calling
> pinctrl_generic_group_name_to_selector() and radix_tree_insert() so we probably won't
> see it in real hardware tests.

Hmm but that race should be already fixed with mutex held
by the pin controller drivers with these fixes? Or am I
missing something still?

Regards,

Tony