On Tue, Nov 24, 2020 at 5:19 PM David Laight <david.lai...@aculab.com> wrote:
>
> From: Arnd Bergmann
> > Sent: 24 November 2020 15:18
> >
> > The ethtool compat ioctl handling is hidden away in net/socket.c,
> > which introduces a couple of minor oddities:
> >
> ...
> > +
> > +static int ethtool_rxnfc_copy_from_compat(struct ethtool_rxnfc *rxnfc,
> > + const struct compat_ethtool_rxnfc
> > __user *useraddr,
> > + size_t size)
> > +{
>
> I think this (and possibly others) want a 'noinline_for_stack'.
> So that both the normal and compat structures aren't both on the
> stack when the real code is called.
Yes, makes sense. I checked that the difference is small unless
CONFIG_KASAN_STACK is enabled, and that gcc is smart enough
not to inline these by default, but adding noinline_for_stack is
both consistent with the rest of the file and the safe bet here.
Arnd
