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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 6 Apr 2023 13:20:52 +0300
Message-ID: <CAHp75Vf-nG865UwbVjwFjVTtXA7mAdi4FfKCpTHDx55eFnbvAA@mail.gmail.com>
Subject: Re: [PATCH 6/9] fortify: Split reporting and avoid passing string pointer
To:     Kees Cook <keescook@chromium.org>
Cc:     linux-hardening@vger.kernel.org, Andy Shevchenko <andy@kernel.org>,
        Cezary Rojewski <cezary.rojewski@intel.com>,
        Puyou Lu <puyou.lu@gmail.com>, Mark Brown <broonie@kernel.org>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Brendan Higgins <brendan.higgins@linux.dev>,
        David Gow <davidgow@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Alexander Potapenko <glider@google.com>,
        Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Miguel Ojeda <ojeda@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Liam Howlett <liam.howlett@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Dan Williams <dan.j.williams@intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Yury Norov <yury.norov@gmail.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Sander Vanheule <sander@svanheule.net>,
        Eric Biggers <ebiggers@google.com>,
        "Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Daniel Latypov <dlatypov@google.com>,
        =?UTF-8?B?Sm9zw6kgRXhww7NzaXRv?= <jose.exposito89@gmail.com>,
        linux-kernel@vger.kernel.org, kunit-dev@googlegroups.com
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On Thu, Apr 6, 2023 at 3:02=E2=80=AFAM Kees Cook <keescook@chromium.org> wr=
ote:
>
> In preparation for KUnit testing and further improvements in fortify
> failure reporting, split out the report and encode the function and
> access failure (read or write overflow) into a single int argument. This
> mainly ends up saving some space in the data segment. For a defconfig
> with FORTIFY_SOURCE enabled:
>
> $ size gcc/vmlinux.before gcc/vmlinux.after
>    text           data     bss     dec              hex filename
> 26132309        9760658 2195460 38088427        2452eeb gcc/vmlinux.befor=
e
> 26132386        9748382 2195460 38076228        244ff44 gcc/vmlinux.after

...

> +       const char *name;
> +       const bool write =3D !!(reason & 0x1);

Perhaps define that as

FORTIFY_READ_WRITE  BIT(0)
FORTIFY_FUNC_SHIFT  1

const bool write =3D reason & FORTIFY_READ_WRITE; // and note no need for !=
! part

switch (reason >> FORTIFY_FUNC_SHIFT) {

> +       switch (reason >> 1) {
> +       case FORTIFY_FUNC_strncpy:
> +               name =3D "strncpy";
> +               break;
> +       case FORTIFY_FUNC_strnlen:
> +               name =3D "strnlen";
> +               break;
> +       case FORTIFY_FUNC_strlen:
> +               name =3D "strlen";
> +               break;
> +       case FORTIFY_FUNC_strlcpy:
> +               name =3D "strlcpy";
> +               break;
> +       case FORTIFY_FUNC_strscpy:
> +               name =3D "strscpy";
> +               break;
> +       case FORTIFY_FUNC_strlcat:
> +               name =3D "strlcat";
> +               break;
> +       case FORTIFY_FUNC_strcat:
> +               name =3D "strcat";
> +               break;
> +       case FORTIFY_FUNC_strncat:
> +               name =3D "strncat";
> +               break;
> +       case FORTIFY_FUNC_memset:
> +               name =3D "memset";
> +               break;
> +       case FORTIFY_FUNC_memcpy:
> +               name =3D "memcpy";
> +               break;
> +       case FORTIFY_FUNC_memmove:
> +               name =3D "memmove";
> +               break;
> +       case FORTIFY_FUNC_memscan:
> +               name =3D "memscan";
> +               break;
> +       case FORTIFY_FUNC_memcmp:
> +               name =3D "memcmp";
> +               break;
> +       case FORTIFY_FUNC_memchr:
> +               name =3D "memchr";
> +               break;
> +       case FORTIFY_FUNC_memchr_inv:
> +               name =3D "memchr_inv";
> +               break;
> +       case FORTIFY_FUNC_kmemdup:
> +               name =3D "kmemdup";
> +               break;
> +       case FORTIFY_FUNC_strcpy:
> +               name =3D "strcpy";
> +               break;
> +       default:
> +               name =3D "unknown";
> +       }

...

> +       WARN(1, "%s: detected buffer %s overflow\n", name, write ? "write=
" : "read");

Using str_read_write() ?

Dunno if it's already there or needs to be added. I have some patches
to move those str_*() to string_choices.h. We can also prepend yours
with those.

--=20
With Best Regards,
Andy Shevchenko