On Fri, Jul 06, 2018 at 12:08:14PM -0700, Matthew Wilcox wrote:
> On Fri, Jul 06, 2018 at 09:26:46PM +0300, Dan Carpenter wrote:
> > On Fri, Jul 06, 2018 at 10:51:30AM -0700, Matthew Wilcox wrote:
> > > On Fri, Jul 06, 2018 at 08:21:01PM +0300, Dan Carpenter wrote:
> > > > We need to unlock on this error path.
> > > >
> > > > Fixes: 29a6bfc32eb2 ("xarray: Track free entries in an XArray")
> > > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > > > ---
> > > >
> > > > There "UINT_MAX + 1" is an integer overflow and is equal to zero but I
> > > > don't know what was intended there.
> > >
> > > Ah. I didn't realise UINT_MAX was defined as ~0U. I had intended
> > > UINT_MAX + 1UL. ie 0x10000000UL on 64-bit and 0 on 32-bit.
> > >
> >
> > I will push a Smatch check so that the wrap around on 32 bit systems
> > will generate a warning.
>
> Do you mean "on 64-bit systems"? Because the code as-written was correct
> on 32-bit systems and buggy on 64-bit systems.
>
> I suppose generally, this is:
>
> if (unsigned long == unsigned int + int)
>
> where we can tell statically that the right hand side will wrap on 32-bit
> systems and not on 64-bit systems.
No no. I'm going to print a warning any time you add two numbers
together and it wraps around. It's normally a bug.
One idea to silence the warning would be to use #ifdef 64BIT #else.
regards,
dan carpenter
