linux-kernel - Re: [PATCH 3/4] char/tpm: Improve a size determination in nine functions

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Date:   Tue, 17 Oct 2017 14:58:18 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
cc:     Alexander.Steffen@...ineon.com, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, andriy.shevchenko@...ux.intel.com,
        elfring@...rs.sourceforge.net, linux-integrity@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, benh@...nel.crashing.org,
        clabbe.montjoie@...il.com, jarkko.sakkinen@...ux.intel.com,
        jgunthorpe@...idianresearch.com, jsnitsel@...hat.com,
        kgold@...ux.vnet.ibm.com, mpe@...erman.id.au,
        nayna@...ux.vnet.ibm.com, paulus@...ba.org, PeterHuewe@....de,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/4] char/tpm: Improve a size determination in nine
 functions



On Tue, 17 Oct 2017, Mimi Zohar wrote:

> On Tue, 2017-10-17 at 11:50 +0000, Alexander.Steffen@...ineon.com
> wrote:
> > > > Replace the specification of data structures by pointer dereferences
> > > > as the parameter for the operator "sizeof" to make the corresponding
> > > > size
> > > > determination a bit safer according to the Linux coding style
> > > > convention.
> > >
> > >
> > > This patch does one style in favor of the other.
> >
> > I actually prefer that style, so I'd welcome this change :)
>
> Style changes should be reviewed and documented, like any other code
> change, and added to Documentation/process/coding-style.rst or an
> equivalent file.

Actually, it has been there for many years:

14) Allocating memory
---------------------
...
The preferred form for passing a size of a struct is the following:

.. code-block:: c

	p = kmalloc(sizeof(*p), ...);

The alternative form where struct name is spelled out hurts readability and
introduces an opportunity for a bug when the pointer variable type is changed
but the corresponding sizeof that is passed to a memory allocator is not.

julia

>
> > > At the end it's Jarkko's call, though I would NAK this as I think some
> > > one already told this to you for some other similar patch(es).
> > >
> > >
> > > I even would suggest to stop doing this noisy stuff, which keeps people
> > > busy for nothing.
> >
> > Cleaning up old code is also worth something, even if does not
> > change one bit in the assembly output in the end...
>
> Wow, you're opening the door really wide for all sorts of trivial
> changes!  Hope you have the time and inclination to review and comment
> on all of them.  I certainly don't.
>
> There is a major difference between adding these sorts of checks to
> the tools in the scripts directory or even to the zero day bots that
> catch different sorts of errors, BEFORE code is upstreamed, and
> patches like these, after the fact.
>
> After the code has been upstreamed, it is a lot more difficult to
> justify changes like this.  It impacts both code that is being
> developed AND backporting bug fixes.
>
> Mimi
>
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