Re: graft_tree/attach_mnt rfc

From: Mike Wray (mike_wrayat_private)
Date: Tue Oct 01 2002 - 02:51:18 PDT

  • Next message: Serge E. Hallyn: "Re: graft_tree/attach_mnt rfc"

    >From: Serge E. Hallyn <hallynat_private>
    >Sent: 30 September 2002 09:28
    
    
    > > > label.  Is attaching a tree to the namespace something that needs to
    be
    > > > mediated, or simply recorded?
    > > >
    > >
    > > Anyone using a security policy that derives inode security
    > > information from the namespace needs to follow additions and removals
    > > in the namespace, not just references to superblocks.
    > > We do it that way for one.
    >
    > He's not asking whether we want record, but whether we are willing
    > *only* to record, and not mediate.
    >
    > If we only record, DTE can no longer say "this fs can't be mounted under
    > this pathname."  But it does make for a far cleaner patch, and I can
    > still intercept the attach in order to pretend it was mounted elsewhere.
    >
    > So, given how much cleaner Chris' patch is, I'd say simply recording is
    > the better way to go.
    >
    > Unless someone else needs to mediate?
    
    It looks like you are proposing that it should no longer be possible
    to veto a loopback mount with an LSM security hook, and that
    only controls for do_kern_mount() should remain.
    Like I said, we need to record all namespace operations,
    but we need to be able to veto a loopback mount too (mediate),
    so I'd be against that.
    
    BTW, in Serge and Chris's patches moving the sb_post_addmount hook
    from the end of graft_tree() into attach_mount() means that it
    would be called with the dcache_lock held - whereas before
    it wasn't. It also means that sb_post_addmount() might be called
    multiple times on one mount (via copy_tree()).
    
    Mike Wray
    
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