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

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Message-ID: <Ygq4wy9fikDYmuHU@zeniv-ca.linux.org.uk>
Date:   Mon, 14 Feb 2022 20:17:07 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
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Subject: Re: [PATCH 04/14] x86: use more conventional access_ok() definition

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@...nel.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...