linux-kernel - Re: [PATCH net-next] modules: allow modprobe load regular elf binaries

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Date:   Fri, 9 Mar 2018 10:43:04 -0800
From:   Kees Cook <keescook@...omium.org>
To:     David Miller <davem@...emloft.net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexei Starovoitov <ast@...com>,
        Andy Lutomirski <luto@...capital.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Djalal Harouni <tixxdz@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Daniel Borkmann <daniel@...earbox.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH net-next] modules: allow modprobe load regular elf binaries

On Fri, Mar 9, 2018 at 10:35 AM, David Miller <davem@...emloft.net> wrote:
> From: Linus Torvalds <torvalds@...ux-foundation.org>
> Date: Fri, 9 Mar 2018 10:17:42 -0800
>
>>  - use deny_write_access() to make sure that we don't have active
>> writers and cannot get them during the execve.
>
> I agree that this is necessary for image validation purposes.

Module loading (via kernel_read_file()) already uses
deny_write_access(), and so does do_open_execat(). As long as module
loading doesn't call allow_write_access() before the execve() has
started in the new implementation, I think we'd be covered here.

-Kees

-- 
Kees Cook
Pixel Security