linux-kernel - Re: [PATCH 04/14] x86: use more conventional access

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Date:   Mon, 14 Feb 2022 21:00:11 +0100
From:   Christoph Hellwig <hch@....de>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
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        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 04/14] x86: use more conventional access_ok() definition

On Mon, Feb 14, 2022 at 08:45:52PM +0100, Arnd Bergmann wrote:
> As Al pointed out, they turned out to be necessary on sparc64, but the only
> definitions are on sparc64 and x86, so it's possible that they serve a similar
> purpose here, in which case changing the limit from TASK_SIZE to
> TASK_SIZE_MAX is probably wrong as well.
> 
> So either I need to revert the original definition as I did on sparc64, or
> they can be removed completely. Hopefully Al or the x86 maintainers
> can clarify.

Looking at the x86 users I think:

 - valid_user_frame should go away and the caller should use get_user
   instead of __get_user
 - the one in copy_code can just go away, as there is another check
   in copy_from_user_nmi
 - copy_stack_frame should just use access_ok
 - as does copy_from_user_nmi

but yes, having someone who actually knows this code look over it
would be very helpful.