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Drivers: hv: vmbus: fix the race when querying & updating the percpu list

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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: Rolf Neugebauer <rolf.neugebauer@docker.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dexuan Cui
2016-06-09 18:47:24 -07:00
committed by Greg Kroah-Hartman
parent e0fa3e5e7d
commit 638fea33ae
3 changed files with 33 additions and 8 deletions
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6
drivers/hv/channel.c
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@@ -505,7 +505,6 @@ static void reset_channel_cb(void *arg)
static int vmbus_close_internal(struct vmbus_channel *channel)
{
struct vmbus_channel_close_channel *msg;
struct tasklet_struct *tasklet;
int ret;
/*
@@ -517,8 +516,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
* To resolve the race, we can serialize them by disabling the
* tasklet when the latter is running here.
*/
tasklet = hv_context.event_dpc[channel->target_cpu];
tasklet_disable(tasklet);
hv_event_tasklet_disable(channel);
/*
* In case a device driver's probe() fails (e.g.,
@@ -584,7 +582,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
get_order(channel->ringbuffer_pagecount * PAGE_SIZE));
out:
tasklet_enable(tasklet);
hv_event_tasklet_enable(channel);
return ret;
}