[PATCH RESEND] pinctrl: single: fix potential NULL dereference in pcs_get_function()

[Ma Ke]

Andrew Morton<akpm at linux-foundation.org> wrote:
> On Wed, 21 Aug 2024 14:21:32 +0800 Ma Ke <make24 at iscas.ac.cn> wrote:
> 
> > pinmux_generic_get_function() can return NULL and the pointer 'function'
> > was dereferenced without checking against NULL. Add checking of pointer
> > 'function' in pcs_get_function().
> > 
> > Found by code review.
> > 
> > ...
> >
> > --- a/drivers/pinctrl/pinctrl-single.c
> > +++ b/drivers/pinctrl/pinctrl-single.c
> > @@ -345,6 +345,8 @@ static int pcs_get_function(struct pinctrl_dev *pctldev, unsigned pin,
> >  		return -ENOTSUPP;
> >  	fselector = setting->func;
> >  	function = pinmux_generic_get_function(pctldev, fselector);
> > +	if (!function)
> > +		return -EINVAL;
> >  	*func = function->data;
> >  	if (!(*func)) {
> >  		dev_err(pcs->dev, "%s could not find function%i\n",
> 
> Maybe.  Or maybe pinmux_generic_get_function() must always return a
> valid pointer, in which case
> 
> 	BUG_ON(!function);
> 
> is an appropriate thing.  But a null-pointer deref gives us the same
> info, so no change is needed.
> 
> btw, pinmux_generic_get_function() is funny:
> 
> 	if (!function)
> 		return NULL;
> 
> 	return function;
Thank you for your response to the vulnerability I submitted. Yes, we 
believe there is a similar issue. As described in [1], 
pinmux_generic_get_function() could return as NULL and lead to a d
ereferencing problem, and a similar issue exists in this code. It is better
to add checking of pointer 'function' in pcs_get_function(). The discovery 
of this problem was confirmed through manual review of the code and 
compilation testing.

[1] https://lore.kernel.org/linux-arm-kernel/CACRpkdYwBNjGzODYqvz+oScsO3u=R0dXMkP4UfqmosDugPFWRA@mail.gmail.com/T/

--
Regards,

Ma Ke