vmbus: hvsock: add proper sync for vmbus_hvsock_device_unregister()

dcui · gregkh · commit 9d35593b4f0b · 2017-10-20T14:56:25.000+02:00
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 &lt;decui@microsoft.com&gt;
Cc: Haiyang Zhang &lt;haiyangz@microsoft.com&gt;
Cc: Stephen Hemminger &lt;sthemmin@microsoft.com&gt;
Signed-off-by: K. Y. Srinivasan &lt;kys@microsoft.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
diff --git 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);

Original file line number	Diff line number	Diff line change
`@@ -937,7 +937,10 @@ void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)`
`937`	`937`	`{`
`938`	`938`	`BUG_ON(!is_hvsock_channel(channel));`
`939`	`939`
`940`		`- channel->rescind = true;`
	`940`	`+ /* We always get a rescind msg when a connection is closed. */`
	`941`	`+ while (!READ_ONCE(channel->probe_done) \|\| !READ_ONCE(channel->rescind))`
	`942`	`+ msleep(1);`
	`943`	`+`
`941`	`944`	`vmbus_device_unregister(channel->device_obj);`
`942`	`945`	`}`
`943`	`946`	`EXPORT_SYMBOL_GPL(vmbus_hvsock_device_unregister);`