[PATCH 4.18 109/235] vmbus: dont return values for uninitalized channels

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>

commit 6712cc9c22117a8af9f3df272b4a44fd2e4201cd upstream.

For unsupported device types, the vmbus channel ringbuffer is never
initialized, and therefore reading the sysfs files will return garbage
or cause a kernel OOPS.

Fixes: c2e5df616e1a ("vmbus: add per-channel sysfs info")

Signed-off-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.15
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/hv/vmbus_drv.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1178,6 +1178,9 @@ static ssize_t vmbus_chan_attr_show(stru
 	if (!attribute->show)
 		return -EIO;
 
+	if (chan->state != CHANNEL_OPENED_STATE)
+		return -EINVAL;
+
 	return attribute->show(chan, buf);
 }