linux-hardening - Re: [PATCH for-next 15/25] fortify: Move remaining fortify helpers into fortify-string.h

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Message-ID: <CAKwvOdk0TC_D3ZOQF38=hqH3JRJ608HfzcnczmDunEF5_t0Buw@mail.gmail.com>
Date:   Wed, 25 Aug 2021 14:59:24 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Francis Laniel <laniel_francis@...vacyrequired.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Daniel Micay <danielmicay@...il.com>,
        Bart Van Assche <bvanassche@....org>,
        David Gow <davidgow@...gle.com>, linux-mm@...ck.org,
        clang-built-linux@...glegroups.com, linux-hardening@...r.kernel.org
Subject: Re: [PATCH for-next 15/25] fortify: Move remaining fortify helpers
 into fortify-string.h

On Sun, Aug 22, 2021 at 12:57 AM Kees Cook <keescook@...omium.org> wrote:
>
> When commit a28a6e860c6c ("string.h: move fortified functions definitions
> in a dedicated header.") moved the fortify-specific code, some helpers
> were left behind. Move the remaining fortify-specific helpers into
> fortify-string.h so they're together where they're used. This requires
> that any FORTIFY helper function prototypes be conditionally built to
> avoid "no prototype" warnings. Additionally removes unused helpers.
>
> Acked-by: Francis Laniel <laniel_francis@...vacyrequired.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  include/linux/fortify-string.h | 7 +++++++
>  include/linux/string.h         | 9 ---------
>  lib/string_helpers.c           | 2 ++
>  3 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
> index c1be37437e77..7e67d02764db 100644
> --- a/include/linux/fortify-string.h
> +++ b/include/linux/fortify-string.h
> @@ -2,6 +2,13 @@
>  #ifndef _LINUX_FORTIFY_STRING_H_
>  #define _LINUX_FORTIFY_STRING_H_
>
> +#define __FORTIFY_INLINE extern __always_inline __attribute__((gnu_inline))
> +#define __RENAME(x) __asm__(#x)
> +
> +void fortify_panic(const char *name) __noreturn __cold;
> +void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)");
> +void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)");
> +void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)");
>
>  #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
>  extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr);
> diff --git a/include/linux/string.h b/include/linux/string.h
> index b48d2d28e0b1..9473f81b9db2 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -249,15 +249,6 @@ static inline const char *kbasename(const char *path)
>         return tail ? tail + 1 : path;
>  }
>
> -#define __FORTIFY_INLINE extern __always_inline __attribute__((gnu_inline))
> -#define __RENAME(x) __asm__(#x)
> -
> -void fortify_panic(const char *name) __noreturn __cold;
> -void __read_overflow(void) __compiletime_error("detected read beyond size of object passed as 1st parameter");
> -void __read_overflow2(void) __compiletime_error("detected read beyond size of object passed as 2nd parameter");
> -void __read_overflow3(void) __compiletime_error("detected read beyond size of object passed as 3rd parameter");
> -void __write_overflow(void) __compiletime_error("detected write beyond size of object passed as 1st parameter");
> -
>  #if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
>  #include <linux/fortify-string.h>
>  #endif
> diff --git a/lib/string_helpers.c b/lib/string_helpers.c
> index e9433caab217..1274f45ffaf4 100644
> --- a/lib/string_helpers.c
> +++ b/lib/string_helpers.c
> @@ -879,9 +879,11 @@ char *strreplace(char *s, char old, char new)
>  }
>  EXPORT_SYMBOL(strreplace);
>
> +#ifdef CONFIG_FORTIFY_SOURCE
>  void fortify_panic(const char *name)
>  {
>         pr_emerg("detected buffer overflow in %s\n", name);
>         BUG();
>  }
>  EXPORT_SYMBOL(fortify_panic);
> +#endif /* CONFIG_FORTIFY_SOURCE */
> --
> 2.30.2
>
> --
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-- 
Thanks,
~Nick Desaulniers