RDMA/erdma: Hold CQ references when processing EQ events

In the Linux kernel, the following vulnerability has been resolved: RDMA/erdma: Hold CQ references when processing EQ events EQ handlers look up CQs from dev->cq_xa and invoke CQ completion or error callbacks outside the xarray lock. erdma_destroy_cq() can erase the CQ from the xarray and free its queue buffer and doorbell record while a previously scheduled EQ handler is still using the CQ. Add a CQ refcount and take a reference under the xarray lock with refcount_inc_not_zero(). Remove the CQ from the xarray before dropping the destroy-path reference, then wait for in-flight EQ users before releasing CQ resources.

Where it's fixed