Subject: Re: [PATCH] PCI: rockchip-dwc: Potential error pointer dereference in probe

From: Dan Carpenter <[email-masked]>
Date: Fri, 13 Aug 2021 16:54:12 +0300

On Fri, Aug 13, 2021 at 01:55:38PM +0100, Robin Murphy wrote:
> On 2021-08-13 12:33, Dan Carpenter wrote:
> > If devm_regulator_get_optional() returns an error pointer, then we
> > should return it to the user.  The current code makes an exception
> > for -ENODEV that will result in an error pointer dereference on the
> > next line when it calls regulator_enable().  Remove the exception.
> 
> Doesn't this break the apparent intent of the regulator being optional,
> though?

Argh...  Crap.  My patch is wrong, but the bug is real.

This code should follow the standard kernel idiom of returning error
pointers when there are errors and returning NULL when an optional
feature is disabled.  The problem with returning a Special Error code
to mean "disabled" is that someone will use the Special Error code to
mean an error.

And that has already sort of happened, because _regulator_get() returns
-ENODEV which would will cause the Oops I described in my patch.

Ugh...  The correct thing is to convert it to NULL/error pointers.  I
have not looked at how hard that is though...

regards,
dan carpenter

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