Without the patch, vmbus_hvsock_device_unregister() can destroy the device
prematurely when close() is called, and can cause NULl dereferencing or
potential data loss (the last portion of the data stream may be dropped
prematurely).

Signed-off-by: Dexuan Cui <de...@microsoft.com>
Cc: K. Y. Srinivasan <k...@microsoft.com>
Cc: Haiyang Zhang <haiya...@microsoft.com>
Cc: Stephen Hemminger <sthem...@microsoft.com>
---

The patch is rebased on today's char-misc tree's char-misc-linus branch.
Please consider it for v4.14.

 drivers/hv/channel_mgmt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 018d2e0..379b0df 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -937,7 +937,10 @@ void vmbus_hvsock_device_unregister(struct vmbus_channel 
*channel)
 {
        BUG_ON(!is_hvsock_channel(channel));
 
-       channel->rescind = true;
+       /* We always get a rescind msg when a connection is closed. */
+       while (!READ_ONCE(channel->probe_done) || !READ_ONCE(channel->rescind))
+               msleep(1);
+
        vmbus_device_unregister(channel->device_obj);
 }
 EXPORT_SYMBOL_GPL(vmbus_hvsock_device_unregister);
-- 
2.7.4

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