From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH 04/14] x86: use more conventional access_ok() definition
Date: Mon, 14 Feb 2022 20:17:07 +0000
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arnd Bergmann <arnd@kernel.org>, Christoph Hellwig <hch@infradead.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>, the

On Mon, Feb 14, 2022 at 12:01:05PM -0800, Linus Torvalds wrote:
> On Mon, Feb 14, 2022 at 11:46 AM Arnd Bergmann <arnd@kernel.org> 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.
> 
> x86-64 has always(*) used TASK_SIZE_MAX for access_ok(), and the
> get_user() assembler implementation does the same.
> 
> I think any __range_not_ok() users that use TASK_SIZE are entirely
> historical, and should be just fixed.

IIRC, that was mostly userland stack trace collection in perf.
I'll try to dig in archives and see what shows up - it's been
a while ago...