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    Subject[PATCH 4.14 108/137] RDMA/uverbs: Atomically flush and mark closed the comp event queue
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Steve Wise <swise@opengridcomputing.com>

    commit 67e3816842fe6414d629c7515b955952ec40c7d7 upstream.

    Currently a uverbs completion event queue is flushed of events in
    ib_uverbs_comp_event_close() with the queue spinlock held and then
    released. Yet setting ev_queue->is_closed is not set until later in
    uverbs_hot_unplug_completion_event_file().

    In between the time ib_uverbs_comp_event_close() releases the lock and
    uverbs_hot_unplug_completion_event_file() acquires the lock, a completion
    event can arrive and be inserted into the event queue by
    ib_uverbs_comp_handler().

    This can cause a "double add" list_add warning or crash depending on the
    kernel configuration, or a memory leak because the event is never dequeued
    since the queue is already closed down.

    So add setting ev_queue->is_closed = 1 to ib_uverbs_comp_event_close().

    Cc: stable@vger.kernel.org
    Fixes: 1e7710f3f656 ("IB/core: Change completion channel to use the reworked objects schema")
    Signed-off-by: Steve Wise <swise@opengridcomputing.com>
    Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/infiniband/core/uverbs_main.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/drivers/infiniband/core/uverbs_main.c
    +++ b/drivers/infiniband/core/uverbs_main.c
    @@ -424,6 +424,7 @@ static int ib_uverbs_comp_event_close(st
    list_del(&entry->obj_list);
    kfree(entry);
    }
    + file->ev_queue.is_closed = 1;
    spin_unlock_irq(&file->ev_queue.lock);

    uverbs_close_fd(filp);

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