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

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Message-Id: <E459E6CC-F51B-4F2A-9D26-FFB7166E0A47@amacapital.net>
Date:   Fri, 9 Mar 2018 10:48:51 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Alexei Starovoitov <ast@...com>, Kees Cook <keescook@...omium.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Djalal Harouni <tixxdz@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        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 Mar 9, 2018, at 10:17 AM, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 

> 
> Hmm. I wish we had an "execute blob" model, but we really don't, and
> it would be hard/impossible to do without pinning the pages in memory.
> 

Why so hard?  We can already execute a struct file for execveat, and Alexei already has this working for umh. Surely we can make an immutable (as in even root can’t write it) kernel-internal tmpfs file, execveat it, then unlink it. And /proc/PID/exe should be openable and readable.  The blob itself would be __initdata so it gets discarded after it lands in tmpfs.