linux-kernel - Re: [PATCH 03/14] nds32: fix access_ok() checks in get/put

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Date:   Tue, 15 Feb 2022 10:18:15 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        linux-arch <linux-arch@...r.kernel.org>,
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Subject: Re: [PATCH 03/14] nds32: fix access_ok() checks in get/put_user

On Mon, Feb 14, 2022 at 6:01 PM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Mon, Feb 14, 2022 at 05:34:41PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > 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?

I had another look, but I think that would be a bigger change than
I want to have in a fix for stable backports, as nds32 also uses
the _check versions in __{get,put}_user_error.

If we instead clean it up in a separate patch, it should be done for
all eight architectures that do the same thing, but at that point,
the time seems better spent at coming up with a new set of
calling conventions that work with asm-goto.

         Arnd