From 6712cc9c22117a8af9f3df272b4a44fd2e4201cd Mon Sep 17 00:00:00 2001
From: Stephen Hemminger <stephen@networkplumber.org>
Date: Mon, 20 Aug 2018 21:16:40 +0000
Subject: [PATCH] vmbus: don't return values for uninitalized channels

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@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: <stable@vger.kernel.org> # 4.15
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/hv/vmbus_drv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index b1b548a21f91..c71cc857b649 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1291,6 +1291,9 @@ static ssize_t vmbus_chan_attr_show(struct kobject *kobj,
 	if (!attribute->show)
 		return -EIO;
 
+	if (chan->state != CHANNEL_OPENED_STATE)
+		return -EINVAL;
+
 	return attribute->show(chan, buf);
 }