linux-hardening - Re: [PATCH v4] drivers/iio: Remove all strcpy() uses

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Date:   Sun, 15 Aug 2021 09:58:02 -0700
From:   Joe Perches <joe@...ches.com>
To:     Len Baker <len.baker@....com>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        David Laight <David.Laight@...lab.com>,
        Kees Cook <keescook@...omium.org>,
        linux-hardening@...r.kernel.org,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] drivers/iio: Remove all strcpy() uses

On Sun, 2021-08-15 at 18:36 +0200, Len Baker wrote:
> Hi Joe,

Hello Len.

Don't take this advice too seriously, it's just bikeshedding
but it seems to me an unexpected use of a strcmp equivalent
in a non performance sensitive path.
 
> On Sun, Aug 15, 2021 at 08:06:45AM -0700, Joe Perches wrote:
[]
> > bikeshed:
> > 
> > I think this change is less intelligible than the original strcmp.
> 
> So, if I understand correctly you suggest to change the above line for:
>                               else if (strcmp(orient, "0") == 0)

Yes.

In kernel sources it's about 2:1 in favor of '!strcmp()' over 'strcmp() == 0'

$ git grep -P '\!\s*strcmp\b' | wc -l
3457
$ git grep -P '\bstrcmp\s*\([^\)]+\)\s*==\s*0\b' | wc -l
1719

And it's your choice to use one or the other or just your V4 patch.

btw, according to godbolt:

gcc -O2 doesn't call strcmp and produces the same object code as your
byte comparisons.  clang 11 calls strcmp regardless of optimization level.