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    Subject[RFC][PATCH 0/4] utsns: RPC/NFS bug rework
    This series replaces the workaround for a bug reported by Cedric Le Goater 
    <> back in September:

    > On a system with nfs mounts, if a task unshares its mount namespace,
    > a oops can occur when the system is rebooted if the task is the last
    > to unreference the nfs mount. It will try to create a rpc request
    > using utsname() which has been invalidated by free_nsproxy().

    Cedric worked around this bug by always using the initial uts namespace's
    nodename (see commit: 63ffc23d307c9534c732edd87895e37b223004a3).

    This is a non-ideal solution because uts namespace nodenames are reported
    as the hostname during RPC authentication. Consider a machine configured
    to export directories via NFS from a parent container to designated "trusted"
    child containers. It would be unable to rely on the hostname during RPC
    authentication -- forcing the administration of more advanced authentication
    systems than might otherwise be necessary.

    The goal of this series is to report a namespace's UTS nodename rather than
    the initial UTS namespace's nodename during RPC-call authentication -- much as
    before Cedric's workaround. By changing the way that the nodename is cached and
    fetched we can simultaneously avoid the NULL dereference during shutdown and
    ensure that amalgamated RPC services (such as statd, lockd, mountd for NFS) see
    a consistent nodename.

    -Matt Helsley


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