Re: [PATCH] perf/ring_buffer: Prefer struct_size over open coded arithmetic

Kees Cook
2024-05-02T22:55:37Z

On Thu, May 02, 2024 at 11:18:37AM +0200, Peter Zijlstra wrote:
> On Wed, May 01, 2024 at 01:21:42PM -0700, Kees Cook wrote:
> > On Tue, Apr 30, 2024 at 11:15:04AM +0200, Peter Zijlstra wrote:
> > > On Mon, Apr 29, 2024 at 07:40:58PM +0200, Erick Archer wrote:
> > > > This is an effort to get rid of all multiplications from allocation
> > > > functions in order to prevent integer overflows [1][2].
> > >
> > > So personally I detest struct_size() because I can never remember wtf it
> > > does, whereas the code it replaces is simple and straight forward :/
> >
> > Sure, new APIs can involved a learning curve. If we can all handle
> > container_of(), we can deal with struct_size(). :)
>
> containre_of() is actually *much* shorter than typing it all out. Which
> is a benefit.
>
> struct_size() not so much. That's just obfuscation for obfuscation's
> sake.

It's really not -- it's making sure that the calculation is semantically
sane: all the right things are being used for the struct size calculation
and things can't "drift", if types change, flex array changes, etc. It's
both a code robustness improvement and a wrap-around stopping improvement.

--
Kees Cook