Subject: Re: [PATCH] mm/nommu.c: Fix improperly call of security API in mmap
From: Eric Paris <eparis@redhat.com>
To: David Howells <dhowells@redhat.com>
Cc: graff.yang@gmail.com, linux-kernel@vger.kernel.org,
       gyang@blackfin.uclinux.org, akpm@linux-foundation.org,
       uclinux-dist-devel@blackfin.uclinux.org,
       Graff Yang <graf.yang@analog.com>,
       linux-security-module@vger.kernel.org
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Date: Fri, 16 Oct 2009 11:21:03 -0400
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On Fri, 2009-10-16 at 16:14 +0100, David Howells wrote:
> Eric Paris <eparis@parisplace.org> wrote:
> 
> > I really don't like seeing such irrelevant (that's not the right word,
> > but I can't think what is) ifdefs creeping down into the security
> > layer as LSM authors are likely to mess them up in the future.  I'd
> > probably rather see the addr_only argument changed into a flags field.
> >  One for addr_only and one flag for not_addr.  The nommu case could
> > just set the not_addr flag and it's obvious how the LSMs (or
> > capabilities if !CONFIG_SECURITY) should handle it, also works if some
> > other future need arises...
> 
> A better way still, might be to deny the possibility of CONFIG_SECURITY if
> CONFIG_MMU=n.  After all, security is sort of pointless when a userspace
> program can just edit the kernel at a whim.

That would still call cap_file_mmap() and wouldn't solve your problem.

-Eric

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