Subject: Re: [PATCH net] net: axienet: fix a signedness bug in probe

From: Dan Carpenter <[email-masked]>
Date: Thu, 26 Sep 2019 16:18:11 +0300

On Wed, Sep 25, 2019 at 01:05:43PM +0200, Alvaro G. M wrote:
> Hi, Dan
> 
> On Wed, Sep 25, 2019 at 01:59:11PM +0300, Dan Carpenter wrote:
> > The "lp->phy_mode" is an enum but in this context GCC treats it as an
> > unsigned int so the error handling is never triggered.
> > 
> >  		lp->phy_mode = of_get_phy_mode(pdev->dev.of_node);
> > -		if (lp->phy_mode < 0) {
> > +		if ((int)lp->phy_mode < 0) {
> 
> This (almost) exact code appears in a lot of different drivers too,
> so maybe it'd be nice to review them all and apply the same cast if needed?
> 

This is a new warning in Smatch.  I did send patches for the whole
kernel.  We won't get these bugs in the future because people run Smatch
on the kernel and will find the bugs.  All the bugs were from 2017 or
later which suggests that someone cleared these out two years ago but
soon the 0-day bot will warn about issues so they will get fixed
quicker.

I'm sort of out of it today...

The get_phy_mode() function seem like they lend themselves to creating
these bugs.  The ->phy_mode variables tend to be declared in the driver
so it would require quite a few patches to make them all int and I'm not
sure that's more beautiful.  Andrew Lunn's idea to update the API would
probably be a good idea.

I'm going back to bed for now and I'll think about this some more.

regards,
dan carpenter