linux-kernel - Re: Does vdso_install attempt to re-compile objects under root privilege?

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Message-ID: <CALCETrVSM0vrMVr2y0ECAQ=tNGvBs=im2Kxongq-jvdzUBevbg@mail.gmail.com>
Date:   Tue, 23 Apr 2019 11:47:34 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        X86 ML <x86@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Does vdso_install attempt to re-compile objects under root privilege?

On Thu, Apr 18, 2019 at 1:08 AM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> Hi.
>
> I have a question about 'vdso_install'.
>
>
> In my understanding, vdso is embedded in the kernel.
> In addition, you can run 'make vdso_install'
> to install an unstripped version of vdso.
> (Mainly, debugging purpose?)
>
> By default, 'make vdso_install' will install it to
> /lib/modules/$(uname -r)/vdso/.
>
>
> Since that directly is owned by root,
> 'make vdso_install' could potentially be
> executed by root, isn't it?
>
>
> Currently, 'vdso_install' depends on vdso,
> so it may cause recompilation of objects
> in the source tree.

Hmm.  I suppose an alternative would be for vdso_install to fail if
the vdso isn't built?

What's the ideal outcome here?