Drivers: hv: vmbus: fix the race when querying & updating the percpu list
There is a rare race when we remove an entry from the global list hv_context.percpu_list[cpu] in hv_process_channel_removal() -> percpu_channel_deq() -> list_del(): at this time, if vmbus_on_event() -> process_chn_event() -> pcpu_relid2channel() is trying to query the list, we can get the kernel fault. Similarly, we also have the issue in the code path: vmbus_process_offer() -> percpu_channel_enq(). We can resolve the issue by disabling the tasklet when updating the list. The patch also moves vmbus_release_relid() to a later place where the channel has been removed from the per-cpu and the global lists. Reported-by: NRolf Neugebauer <rolf.neugebauer@docker.com> Signed-off-by: NDexuan Cui <decui@microsoft.com> Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com> Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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