Message-ID: <5080C100.2090703@zytor.com>
Date: Thu, 18 Oct 2012 19:54:56 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Rusty Russell <rusty@rustcorp.com.au>
CC: mtk.manpages@gmail.com, Kees Cook <keescook@chromium.org>,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        Arnd Bergmann <arnd@arndb.de>,
        James Morris <james.l.morris@oracle.com>,
        Al Viro <viro@zeniv.linux.org.uk>, Eric Paris <eparis@redhat.com>,
        Jiri Kosina <jkosina@suse.cz>, linux-security-module@vger.kernel.org
Subject: Re: [PATCH 1/4] module: add syscall to load module from fd
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On 10/18/2012 07:23 PM, Rusty Russell wrote:
> "H. Peter Anvin" <hpa@zytor.com> writes:
>> Given that, I have to say I now seriously question the value of
>> finit_module().  The kernel can trivially discover if the pointed-to
>> memory area is a MAP_SHARED mmap() of a file descriptor and if so which
>> file descriptor... why can't we handle this behind the scenes?
>
> It is a bit more indirect, but also in practice it's a bit trickier than
> that.  We need to ensure the memory doesn't change underneath us and
> stays attached to that fd.  I can easily see that code slipping and
> ending in an exploit.
>
> But that may be my irrational fear of the mm :)

You have to do the same thing with a file/file descriptor, I would think.

However, I keep wondering about the use case for this, as opposed to 
signatures.

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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