linux-hardening - Re: [PATCH] fortify: Adjust KUnit test for modular build

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Date:   Wed, 14 Sep 2022 18:13:59 +0800
From:   David Gow <davidgow@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-hardening@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fortify: Adjust KUnit test for modular build

On Wed, Sep 14, 2022 at 1:31 AM Kees Cook <keescook@...omium.org> wrote:
>
> A much better "unknown size" string pointer is available directly from
> struct test, so use that instead of a global that isn't shared with
> modules.
>
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Link: https://lore.kernel.org/lkml/YyCOHOchVuE/E7vS@dev-arch.thelio-3990X
> Fixes: 875bfd5276f3 ("fortify: Add KUnit test for FORTIFY_SOURCE internals")
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> Whoops! Thanks Nathan! :) This fixes it for your reproducer.

Ah, this is better than saved_command_line, IMO. I don't think it'd
necessarily be a _disaster_ to just introduce a new dynamically-sized
string here, which would be more explicit, but test->name is at least
obviously related to this file anyway.

Reviewed-by: David Gow <davidgow@...gle.com>

Cheers
-- David

> ---
>  lib/fortify_kunit.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/lib/fortify_kunit.c b/lib/fortify_kunit.c
> index 99bc0ea60d27..409af07f340a 100644
> --- a/lib/fortify_kunit.c
> +++ b/lib/fortify_kunit.c
> @@ -17,7 +17,6 @@
>
>  #include <kunit/test.h>
>  #include <linux/string.h>
> -#include <linux/init.h>
>
>  static const char array_of_10[] = "this is 10";
>  static const char *ptr_of_11 = "this is 11!";
> @@ -31,7 +30,7 @@ static void known_sizes_test(struct kunit *test)
>
>         KUNIT_EXPECT_EQ(test, __compiletime_strlen(array_unknown), SIZE_MAX);
>         /* Externally defined and dynamically sized string pointer: */
> -       KUNIT_EXPECT_EQ(test, __compiletime_strlen(saved_command_line), SIZE_MAX);
> +       KUNIT_EXPECT_EQ(test, __compiletime_strlen(test->name), SIZE_MAX);
>  }
>
>  /* This is volatile so the optimizer can't perform DCE below. */
> --
> 2.34.1
>