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    SubjectRe: [PATCH v5 3/3] cred: change keyctl_session_to_parent() to use task_work_add()
    Date
    Oleg Nesterov <oleg@redhat.com> wrote:

    > Change keyctl_session_to_parent() to use task_work_add() and
    > move key_replace_session_keyring() logic into task_work->func().
    >
    > Note that we do task_work_cancel() before task_work_add() to
    > ensure that only one work can be pending at any time. This is
    > important, we must not allow user-space to abuse the parent's
    > ->task_works list.
    >
    > The callback, replace_session_keyring(), checks PF_EXITING.
    > I guess this is not really needed but looks better.
    >
    > As a side effect, this fixes the (unlikely) race. The callers
    > of key_replace_session_keyring() and keyctl_session_to_parent()
    > lack the necessary barriers, the parent can miss the request.
    >
    > Now we can remove task_struct->replacement_session_keyring and
    > related code.
    >
    > Signed-off-by: Oleg Nesterov <oleg@redhat.com>

    Acked-by: David Howells <dhowells@redhat.com>


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