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    SubjectRe: fanotify - overall design before I start sending patches
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    On Tue, 2009-08-04 at 17:09 +0100, Tvrtko Ursulin wrote:
    > Hi Eric, all,
    >
    > On Friday 24 July 2009 21:13:49 Eric Paris wrote:
    > > If a FAN_ACCESS_PERM or FAN_OPEN_PERM event is received the listener
    > > must send a response before the 5 second timeout. If no response is
    > > sent before the 5 second timeout the original operation is allowed. If
    > > this happens too many times (10 in a row) the fanotify group is evicted
    > > from the kernel and will not get any new events. Sending a response is
    >
    > Would it make more sense to deny on timeouts and then evict? I am thinking it
    > would be more secure with no significant drawbacks. Also for usages like HSM
    > allowing it without data being in place might present wrong content to the
    > user.

    I'd be willing to go that route as long as noone else complains.

    > > The only other current interface is the ability to ignore events by
    > > superblock magic number. This makes it easy to ignore all events
    > > in /proc which can be difficult to accomplish firing FANOTIFY_SET_MARK
    > > with ignored_masks over and over as processes are created and destroyed.
    >
    > Just to double-check, that would also work for any other filesystem and is
    > controllable from userspace?

    Yes you set these in userspace using setsockopt(). It is based on
    superblock magic number as found in linux/magic.h. So one could
    exclude, procfs, sysfs, selinuxfs, etc. It does not provide a way to
    say 'this ext3 filesystem but not that ext3 filesystem' as ext3 has a
    single magic number.



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