linux-kernel - Re: [PATCH 7/7] include/linux/string.h: add the option of fortified string.h functions

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Date:   Sun, 10 Sep 2017 12:55:15 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Kees Cook <keescook@...omium.org>,
        Daniel Micay <danielmicay@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Axtens <dja@...ens.net>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Chris Metcalf <cmetcalf@...hip.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 7/7] include/linux/string.h: add the option of fortified
 string.h functions

Hi Kees, Daniel,

On Mon, Jun 19, 2017 at 10:26 PM, Kees Cook <keescook@...omium.org> wrote:
> From: Daniel Micay <danielmicay@...il.com>
>
> This adds support for compiling with a rough equivalent to the glibc
> _FORTIFY_SOURCE=1 feature, providing compile-time and runtime buffer
> overflow checks for string.h functions when the compiler determines the
> size of the source or destination buffer at compile-time.  Unlike glibc,
> it covers buffer reads in addition to writes.

[...]

> Link: http://lkml.kernel.org/r/20170526095404.20439-1-danielmicay@gmail.com
> Signed-off-by: Daniel Micay <danielmicay@...il.com>
> Acked-by: Kees Cook <keescook@...omium.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Daniel Axtens <dja@...ens.net>
> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Cc: Chris Metcalf <cmetcalf@...hip.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> [kees: move from -mm, add ARCH_HAS_FORTIFY_SOURCE, tweak Kconfig help]
> Signed-off-by: Kees Cook <keescook@...omium.org>

This is now commit 6974f0c4555e285a upstream.

> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -187,4 +187,204 @@ static inline const char *kbasename(const char *path)
>         return tail ? tail + 1 : path;
>  }
>
> +#define __FORTIFY_INLINE extern __always_inline __attribute__((gnu_inline))

With gcc-4.1.2, I now get zillions of:

    include/linux/string.h:439: warning: ‘gnu_inline’ attribute
directive ignored

This attribute seems to be supported as of gcc 4.2?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds