linux-kernel - Re: [PATCH 08/15] maccess: rename strnlen_unsafe_user to strnlen_user

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Message-ID: <20200506174747.GA7549@lst.de>
Date:   Wed, 6 May 2020 19:47:47 +0200
From:   Christoph Hellwig <hch@....de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Christoph Hellwig <hch@....de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-parisc@...r.kernel.org,
        linux-um <linux-um@...ts.infradead.org>,
        Netdev <netdev@...r.kernel.org>, bpf@...r.kernel.org,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/15] maccess: rename strnlen_unsafe_user to
 strnlen_user_unsafe

On Wed, May 06, 2020 at 10:44:15AM -0700, Linus Torvalds wrote:
> So while I think using a consistent convention is good, and it's true
> that there is a difference in the convention between the two cases
> ("unsafe" at the beginning vs end), one of them is actually about the
> safety and security of the operation (and we have automated logic
> these days to verify it on x86), the other has nothing to do with
> "safety", really.
> 
> Would it be better to standardize around a "probe_xyz()" naming?

So:

  probe_strncpy, probe_strncpy_user, probe_strnlen_user?

Sounds weird, but at least it is consistent.

> Or perhaps a "xyz_nofault()" naming?

That sounds a little better:

   strncpy_nofault, strncpy_user_nofault, strnlen_user_nofault

> I realize this is nit-picky, and I think the patch series as-is is
> already an improvement, but I do think our naming in this area is
> really quite bad.

Always open for improvements :)

> The fact that we have "probe_kernel_read()" but then
> "strncpy_from_user_unsafe()" for the _same_ conceptual difference
> really tells me how inconsistent the naming for these kinds of "we
> can't take page faults" is. No?

True.  If we wanted to do _nofaul, what would the basic read/write
versions be?