Re: [PATCH v2][next] cgroup: Avoid -Wstringop-overflow warnings

[Gustavo A. R. Silva]

On 8/16/23 15:01, Tejun Heo wrote:
> On Wed, Aug 16, 2023 at 01:57:16PM -0700, Kees Cook wrote:
> > On Wed, Aug 16, 2023 at 10:51:12AM -1000, Tejun Heo wrote:
> > > Hello,
> > >
> > > On Wed, Aug 16, 2023 at 02:50:16PM -0600, Gustavo A. R. Silva wrote:
> > > > Change the notation from pointer-to-array to pointer-to-pointer.
> > > > With this, we avoid the compiler complaining about trying
> > > > to access a region of size zero as an argument during function
> > > > calls.
> > >
> > > Haha, I thought the functions were actually accessing the memory. This can't
> > > be an intended behavior on the compiler's side, right?
> >
> > I think it's a result of inlining -- the compiler ends up with a case
> > where it looks like it might be possible to index a zero-sized array,
> > but it is "accidentally safe".
>
> Ah I see. It's not that the compiler knows that ** access is safe. It's more
> that it only applies the check on arrays. Is that right? Gustavo, I don't

That's correct.

> mind the patch but can you update the patch description a bit explaining a
> bit more on what's going on with the complier? It doesn't have to be the
> full explanation but it'd be useful to explicitly point out that we're just
> working around the compiler being a bit silly.

I just sent v3:

	https://lore.kernel.org/linux-hardening/ZN5WkbPelHUSTXOA@work/

Thanks
--
Gustavo