Re: [PATCH] iio: imu: adis16480: clean up a condition

[Jonathan Cameron]

On Sun, 6 Oct 2019 21:14:40 +0300
Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:

> On Sun, Oct 06, 2019 at 09:51:33AM +0100, Jonathan Cameron wrote:
> > On Thu, 26 Sep 2019 14:36:30 +0300
> > Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> >   
> > > On Thu, Sep 26, 2019 at 11:06:39AM +0000, Ardelean, Alexandru wrote:  
> > > > On Thu, 2019-09-26 at 11:10 +0300, Dan Carpenter wrote:    
> > > > > [External]
> > > > > 
> > > > > The "t" variable is unsigned so it can't be less than zero.  We really
> > > > > are just trying to prevent divide by zero bugs so just checking against
> > > > > zero is sufficient.  
> > 
> > I'm not sure that true.  It if were signed we'd be detecting that the
> > input from userspace was negative.  
> 
> It does a really bad job of that though so it raises more questions than
> answers.  Maybe just one of the parameters is negative or maybe the
> multiply or the addition overflowed?  Should scenarios those be checked?
> 
> It turns out none of those situations matter, only divide by zero needs
> to be checked.

It isn't being nearly paranoid enough. Either val or val2 being
negative is a reason to fault out.  Divide by zero needs handling after
that.  Obviously divide by zero is the only one that causes a crash but
negatives are going to cause rather 'unexpected' results.

What fun.

Jonathan