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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Stephen Hemminger <sthemmin@microsoft.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>
Subject: [PATCH 4.18 109/235] vmbus: dont return values for uninitalized channels
Date:   Mon, 24 Sep 2018 13:51:35 +0200
Message-Id: <20180924113116.640890602@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Stephen Hemminger <stephen@networkplumber.org>

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@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(+)

--- 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);
 }