From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 04/14] x86: use more conventional access_ok() definition
Date: Mon, 14 Feb 2022 21:00:11 +0100
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To: Arnd Bergmann <arnd@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>, Linus Torvalds <torvalds@linux-foundation.org>, Christoph Hellwig <hch@lst.de>, linux-arch <linux-arch@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>, Linux API <linux-api@vger.kernel.org>, Arnd Bergmann <arnd@arndb.de>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Mark Rutland <mark.rutland@arm.com>, Rich Felker <dalias@libc.org>, linux-ia64@vger.kernel.org, Linux-sh list <linux-sh@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org>, Max Filippov <jcmvbkbc@gmail.com>, Guo Ren <guoren@kernel.org>, sparclinux <sparclinux@vger.kernel.org>, "open list:QUALCOMM HEXAGON..." <linux-hexagon@vger.kernel.org>, linux-riscv <linux-riscv@lists.infradead.org>, Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>, linux-s390 <linux-s390@vger.kernel.org>, Brian Cain <bcain@codeaurora.org>, Helge Deller <deller@gmx.de>

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.