Re: graft_tree/attach_mnt rfc

From: Chris Wright (chrisat_private)
Date: Tue Oct 01 2002 - 12:38:54 PDT

  • Next message: Trent Jaeger: "LSM Verification Tools"

    * Mike Wray (mike_wrayat_private) wrote:
    > 
    > 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.
    
    Well, first, which loopback mount to you mean?  mount -o loop, or
    mount --bind?  Assuming you mean do_loopback (--bind) how do you need to
    control these operations?  Case by case, or simply disabling?
    do_loopback() whether recursive or not eventually calls graft_tree which
    would do the check on the new tree attachment.
    
    > 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.
    
    Yes, this is a known side effect.
    
    > It also means that sb_post_addmount() might be called
    > multiple times on one mount (via copy_tree()).
    
    This is rather intentional so that recursive bind mounts and
    copy_namespace operations get the full picture.
    
    thanks,
    -chris
    -- 
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