linux-kernel - Re: [PATCH v3] lib/string.c: implement stpcpy

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Message-ID: <CAKwvOdnV6GySbhKGVEUBV5GdanR9xRWAFE0JPcpORR=2dmRWPg@mail.gmail.com>
Date:   Mon, 31 Aug 2020 16:21:17 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Kees Cook <keescook@...omium.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Joe Perches <joe@...ches.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        stable <stable@...r.kernel.org>, Andy Lavr <andy.lavr@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        Yury Norov <yury.norov@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] lib/string.c: implement stpcpy

On Thu, Aug 27, 2020 at 1:59 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> strcpy() is not a bad API for the cases when you know what you are
> doing. A problem that most of the developers do not know what they are
> doing.
> No need to split everything to bad and good by its name or semantics,
> each API has its own pros and cons and programmers must use their
> brains.

On Fri, Aug 28, 2020 at 1:17 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> Seems to me that this is a fixation on an abstract problem that never
> exists (of course, if a developer has brains to think).

Of course, no "True Scotsman" would accidentally misuse C string.h API!
https://yourlogicalfallacyis.com/no-true-scotsman

(I will note the irony of my off by one in my v1 implementation of
stpcpy. I've also missed strncpy zeroing the rest of a destination
buffer before.  I might not be a "True Scotsman.")

On Thu, Aug 27, 2020 at 11:30 AM Kees Cook <keescook@...omium.org> wrote:
>
> I equate "unsafe" or "fragile" with "bad". There's no reason to use our
> brains for remembering what's safe or not when we can just remove unsafe
> things from the available APIs, and/or lean on the compiler to help
> (e.g. CONFIG_FORTIFY_SOURCE).

Having seatbelts is great (ie. fortify source), but is no substitute
for driving carefully (having proper APIs that help me not shoot my
foot off).  I think it's nice to have *both*, but if I drove solely
relying on my seatbelts, we might all be in trouble.  Not disagreeing
with you, Kees.
-- 
Thanks,
~Nick Desaulniers