Re: Specifications (the beginning)

From: Philippe Biondi (philippe.biondi@enst-bretagne.fr)
Date: Mon Apr 16 2001 - 07:45:39 PDT

  • Next message: Crispin Cowan: "Re: Benchmarks (was Re: Hooking into Linux using the LTT)"

    On Sun, 15 Apr 2001, Crispin Cowan wrote:
    
    > Philippe Biondi wrote:
    >
    > > On Sat, 14 Apr 2001, Crispin Cowan wrote:
    > > > "module" is the *most* important word in the list name.  There's lots & lots of
    > > > generic security discussion forums, and even lots of linux security discussion
    > > > forums.  I'm trying to chase awasy all of the discussion about the merrits of one
    > > > security model over another, and concentrate on the LSM features needed to support
    > > > a diverse set of security modules.
    > >
    > > I agree if module means modular and not LKM.
    >
    > Yes, it means LKM.  We are not talking about turning Linux into a microkernel here,
    > just adding sufficient functionality to the LKM interface to enable security LKMs to
    > exist (which I've been denoting LSM for "Linux Security Module", hence the list name).
    >
    >
    > > Wanting to make a modular
    > > implementation is important and means that we can get security policies
    > > out of the kernel, in LKMs. Wanting to make a LKM is nonsense, IMHO.
    >
    > I don't really understand what you're saying here.  You seem to be contradicting
    > yourself, but mostly I'm just confused.
    
    Well, let's stop this unproductive nit-picking, I got your point and can
    make mine an yours cohabit as they are close to each other.
    
    >
    > As Greg helpfully reminded me, there are problems asking the kernel to read ASCII from
    > user space files:
    >
    >    * kernel blocking on a disk I/O
    >    * disk read errors
    >    * parsing errors
    >    * etc.
    >
    > So it's best to have a program push the file into the kernel, rather than let the
    > kernel read it direct from a file.  Then the program can fail gracefully, rather than
    > the kernel taking the hit when something goes wrong.
    Agreed. It's even done this way for modules.
    
    
    > > Can these fs work without patching the VFS layer ?
    >
    > By definition, yes:  ext2 supports a form of extended attributes.  You access those
    > attributes with the chattr and lsatter commands.
    > http://www.securityfocus.com/focus/linux/articles/ext2attr.html
    >
    > However, some other extended attributes projects apparently require patching the VFS
    > layer  http://lwn.net/2000/1026/a/extended-attributes.php3
    >
    > I agree with Greg: we don't want to get into a can of worms in the VFS
    > layer.  The trick is to figure out how to allow modules to use
    > extended attributes without getting entangled.
    
    If they are part of one of the VFS structs, modules could take these
    fields in account when taking a decision.
    
    
    
    --
    Philippe Biondi
    Systems administrator
    Webmotion Inc.
    http://www.webmotion.com
    mailto:philippe.biondiat_private
    Fax. (613) 260-9545
    
    
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