linux-hardening - Re: [PATCH for-next 18/25] fortify: Prepare to improve strnlen() and strlen() warnings

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Date:   Wed, 25 Aug 2021 15:01:54 -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 18/25] fortify: Prepare to improve strnlen() and
 strlen() warnings

On Sun, Aug 22, 2021 at 12:57 AM Kees Cook <keescook@...omium.org> wrote:
>
> In order to have strlen() use fortified strnlen() internally, swap their
> positions in the source. Doing this as part of later changes makes
> review difficult, so reoroder it here; no code changes.
>
> Cc: 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 | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
> index 68bc5978d916..a3cb1d9aacce 100644
> --- a/include/linux/fortify-string.h
> +++ b/include/linux/fortify-string.h
> @@ -56,6 +56,17 @@ __FORTIFY_INLINE char *strcat(char *p, const char *q)
>         return p;
>  }
>
> +extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
> +__FORTIFY_INLINE __kernel_size_t strnlen(const char *p, __kernel_size_t maxlen)
> +{
> +       size_t p_size = __builtin_object_size(p, 1);
> +       __kernel_size_t ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size);
> +
> +       if (p_size <= ret && maxlen != ret)
> +               fortify_panic(__func__);
> +       return ret;
> +}
> +
>  __FORTIFY_INLINE __kernel_size_t strlen(const char *p)
>  {
>         __kernel_size_t ret;
> @@ -71,17 +82,6 @@ __FORTIFY_INLINE __kernel_size_t strlen(const char *p)
>         return ret;
>  }
>
> -extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
> -__FORTIFY_INLINE __kernel_size_t strnlen(const char *p, __kernel_size_t maxlen)
> -{
> -       size_t p_size = __builtin_object_size(p, 1);
> -       __kernel_size_t ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size);
> -
> -       if (p_size <= ret && maxlen != ret)
> -               fortify_panic(__func__);
> -       return ret;
> -}
> -
>  /* defined after fortified strlen to reuse it */
>  extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy);
>  __FORTIFY_INLINE size_t strlcpy(char *p, const char *q, size_t size)
> --
> 2.30.2
>
> --
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-- 
Thanks,
~Nick Desaulniers