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

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Message-Id: <1508253453.4234.81.camel@linux.vnet.ibm.com>
Date:   Tue, 17 Oct 2017 11:17:33 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     Julia Lawall <julia.lawall@...6.fr>
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, 2017-10-17 at 14:58 +0200, Julia Lawall wrote:
> 
> 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.

True, thanks for the reminder.  Is this common in new code?  Is there
a script/ or some other automated way of catching this usage before
patches are upstreamed?

Just as you're doing here, the patch description should reference this
in the patch description.

Mimi