RE: [PATCH 03/14] nds32: fix access_ok() checks in get/put_user

[David Laight <David.Laight@xxxxxxxxxx>]

From: Christoph Hellwig
> Sent: 14 February 2022 17:01
> 
> On Mon, Feb 14, 2022 at 05:34:41PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > The get_user()/put_user() functions are meant to check for
> > access_ok(), while the __get_user()/__put_user() functions
> > don't.
> >
> > This broke in 4.19 for nds32, when it gained an extraneous
> > check in __get_user(), but lost the check it needs in
> > __put_user().
> 
> Can we follow the lead of MIPS (which this was originally copied
> from I think) and kill the pointless __get/put_user_check wrapper
> that just obsfucate the code?

Is it possible to make all these architectures fall back to
a common definition somewhere?

Maybe they need to define ACCESS_OK_USER_LIMIT - which can be
different from TASK_SIZE.

There'll be a few special cases, but most architectures have
kernel addresses above userspace ones.

	David

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