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

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Message-ID: <8a6e309687d647e3aef8a88bdb0922af@AcuMS.aculab.com>
Date:   Mon, 14 Feb 2022 17:10:05 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christoph Hellwig' <hch@...radead.org>,
        Arnd Bergmann <arnd@...nel.org>
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        Christoph Hellwig <hch@....de>,
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Subject: RE: [PATCH 03/14] nds32: fix access_ok() checks in get/put_user

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@...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?

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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