Re: [PATCH] pinctrl:sunplus: Add check for kmalloc

[Christophe JAILLET]

Le 23/05/2023 à 21:37, andy.shevchenko@xxxxxxxxx a écrit :
> Tue, May 23, 2023 at 05:39:51PM +0000, Wells Lu 呂芳騰 kirjoitti:
> > > > Fix Smatch static checker warning:
> > > > potential null dereference 'configs'. (kmalloc returns null)
>
> ...
>
> > > >   			configs = kmalloc(sizeof(*configs), GFP_KERNEL);
> > > > +			if (!configs)
> > >
> > > > +				return -ENOMEM;
> > >
> > > "Fixing" by adding a memory leak is not probably a good approach.
> >
> > Do you mean I need to free all memory which are allocated in this subroutine before
> > return -ENOMEM?
>
> This is my understanding of the code. But as I said... (see below)
>
> ...
>
> > > >   			configs = kmalloc(sizeof(*configs), GFP_KERNEL);
> > > > +			if (!configs)
> > > > +				return -ENOMEM;
> > >
> > > Ditto.
>
> ...
>
> > > It might be that I'm mistaken. In this case please add an explanation why in the commit
> > > message.
>
> ^^^

Hmmm, not so sure.

Should be looked at more carefully, but
  dt_to_map_one_config		(in /drivers/pinctrl/devicetree.c)
    .dt_node_to_map
      --> sppctl_dt_node_to_map

Should dt_to_map_one_config() fail, pinctrl_dt_free_maps() is called
(see 
https://elixir.bootlin.com/linux/v6.4-rc1/source/drivers/pinctrl/devicetree.c#L281)

pinctrl_dt_free_maps() calls dt_free_map(), which calls .dt_free_map, so 
pinctrl_utils_free_map()
(see 
https://elixir.bootlin.com/linux/v6.4-rc1/source/drivers/pinctrl/sunplus/sppctl.c#L978)

Finally the needed kfree seem to be called from here.
(see 
https://elixir.bootlin.com/linux/v6.4-rc1/source/drivers/pinctrl/pinctrl-utils.c#L119)


*This should obviously be double checked*, but looks safe to me.


BUT, in the same function, the of_get_parent() should be undone in case 
of error, as done at the end of the function, in the normal path.
This one seems to be missing, should a memory allocation error occur.


Just my 2c,

CJ