linux-kernel - Re: [PATCH 1/5] string.h: add array-wrappers for (v)memdup

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Message-ID: <CAHp75VcNyE9uJu8-v2eVWRdZ3-nm2r-kdxE-naQB4VN6zxPFxg@mail.gmail.com>
Date:   Thu, 31 Aug 2023 16:16:17 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Philipp Stanner <pstanner@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Andy Shevchenko <andy@...nel.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Christian Brauner <brauner@...nel.org>,
        David Disseldorp <ddiss@...e.de>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Siddh Raman Pant <code@...dh.me>,
        Nick Alcock <nick.alcock@...cle.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Zack Rusin <zackr@...are.com>,
        VMware Graphics Reviewers 
        <linux-graphics-maintainer@...are.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, linux-hardening@...r.kernel.org,
        David Airlie <airlied@...hat.com>
Subject: Re: [PATCH 1/5] string.h: add array-wrappers for (v)memdup_user()

On Thu, Aug 31, 2023 at 3:22 PM Philipp Stanner <pstanner@...hat.com> wrote:
> On Wed, 2023-08-30 at 17:11 +0300, Andy Shevchenko wrote:
> > On Wed, Aug 30, 2023 at 4:46 PM Philipp Stanner <pstanner@...hat.com>
> > wrote:

...

> > I'm wondering if this has no side-effects as string.h/string.c IIRC
> > is used also for early stages where some of the APIs are not available.
>
> I forgot to address this point in my previous reply.
>
> Who's going to decide whether this is a problem or not?
>
> My personal guess is that this is unlikely to be a problem because
>
>    A. either (v)memdup_user() is available, in which case
>       (v)memdup_array_user() will always work –
>    B. or (v)memdup_user() is not available, which would cause the code
>       that currently uses (v)memdup_user() for copying arrays to fail
>       anyways.

It also uses something from overflow.h. I don't remember if that
header was ever been used in early stage modules (like
boot/decompressor).

-- 
With Best Regards,
Andy Shevchenko