From: kys@exchange.microsoft.com
To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com,
        vkuznets@redhat.com, jasowang@redhat.com,
        leann.ogasawara@canonical.com
Cc: "K. Y. Srinivasan" <kys@microsoft.com>, <Stable@vger.kernel.org>
Subject: [PATCH 5/5] Drivers: hv: vmbus: Prevent sending data on a rescinded channel
Date: Wed,  7 Dec 2016 01:16:28 -0800
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From: K. Y. Srinivasan <kys@microsoft.com>

After the channel is rescinded, the host does not read from the rescinded channel.
Fail writes to a channel that has already been rescinded. If we permit writes on a
rescinded channel, since the host will not respond we will have situations where
we will be unable to unload vmbus drivers that cannot have any outstanding requests
to the host at the point they are unoaded.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: <Stable@vger.kernel.org>
---
 drivers/hv/ring_buffer.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index cd49cb1..2cd4029 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -298,6 +298,9 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
 	unsigned long flags = 0;
 	struct hv_ring_buffer_info *outring_info = &channel->outbound;
 
+	if (channel->rescind)
+		return -ENODEV;
+
 	for (i = 0; i < kv_count; i++)
 		totalbytes_towrite += kv_list[i].iov_len;
 
@@ -350,6 +353,10 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
 		spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 
 	hv_signal_on_write(old_write, channel, kick_q);
+
+	if (channel->rescind)
+		return -ENODEV;
+
 	return 0;
 }
 
-- 
1.7.4.1