linux-kernel - Re: [PATCH 1/4] module: add syscall to load module from fd

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Message-ID: <loom.20121019T124226-687@post.gmane.org>
Date:	Fri, 19 Oct 2012 10:46:50 +0000 (UTC)
From:	Alon Ziv <alon@...aviz.org>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] module: add syscall to load module from fd

H. Peter Anvin <hpa <at> zytor.com> writes:
> > 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.

Two things:
1. finit_module() lets LSMs make decisions based on full information on the
   module to be loaded
2. On some systems (such as Chromium OS) we have a trusted root OS (e.g. the
   entire root filesystem is protected using dm-verity); requiring signatures
   on top of this is a waste of resources


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