[bionic/linux-azure][PATCH] UBUNTU: SAUCE: vmbus: don't return values for uninitalized channels

[Marcelo Henrique Cerri]

From: Stephen Hemminger <stephen at networkplumber.org>

BugLink: http://bugs.launchpad.net/bugs/1789638

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 at microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys at microsoft.com>
Cc: <stable at vger.kernel.org> # 4.15
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri at canonical.com>
---
 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 610223f0e945..4652990f0298 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1180,6 +1180,9 @@ 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);
 }
 
-- 
2.17.1