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From:   Kees Cook <keescook@chromium.org>
Date:   Tue, 27 Mar 2018 20:34:41 -0700
Message-ID: <CAGXu5jLASUx_SJV-WfKLq5wPXeDpJzBOKneG8q_TjA4jY9w0aA@mail.gmail.com>
Subject: Re: [PATCH v2 05/21] kconfig: remove string expansion in file_lookup()
To:     Masahiro Yamada <yamada.masahiro@socionext.com>
Cc:     linux-kbuild <linux-kbuild@vger.kernel.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Ulf Magnusson <ulfalizer@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Luis R . Rodriguez" <mcgrof@kernel.org>,
        Nicolas Pitre <nico@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, Mar 26, 2018 at 10:29 PM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> There are two callers of file_lookup().
>
> [1] zconf_initscan()
>     This is used to open the first Kconfig.  However, it cannot
>     contain environments in the file path because zconf_fopen() is
>     called before file_lookup().  By swapping the call order,
>     KBUILD_KCONFIG would be able to contain environments, but I do
>     not see practical benefits to support it.
>
> [2] zconf_nextfile()
>     This is used to open the next file from 'source' statement like
>         source "arch/$SRCARCH/Kconfig"
>     but this has already been expanded in the lexer phase.
>
> So, file_lookup() does not need to expand the given path.
>
> By the way, file_lookup() was already buggy; it expanded a given path,
> but it used the path before expansion for look-up:
>         if (!strcmp(name, file->name)) {
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

-- 
Kees Cook
Pixel Security