From: "K. Y. Srinivasan" <kys@microsoft.com>
Date: Tue, 14 Nov 2017 06:53:33 -0700
Patch-mainline: v4.15-rc3
Subject: Drivers: hv: vmbus: Fix a rescind issue
Git-commit: 7fa32e5ec28b1609abc0b797b58267f725fc3964
References: fate#323887

The current rescind processing code will not correctly handle
the case where the host immediately rescinds a channel that has
been offerred. In this case, we could be blocked in the open call and
since the channel is rescinded, the host will not respond and we could
be blocked forever in the vmbus open call.i Fix this problem.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Olaf Hering <ohering@suse.de>
---
 drivers/hv/channel.c      | 10 ++++++++--
 drivers/hv/channel_mgmt.c |  7 ++++---
 include/linux/hyperv.h    |  1 +
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -659,22 +659,28 @@ void vmbus_close(struct vmbus_channel *channel)
 		 */
 		return;
 	}
-	mutex_lock(&vmbus_connection.channel_mutex);
 	/*
 	 * Close all the sub-channels first and then close the
 	 * primary channel.
 	 */
 	list_for_each_safe(cur, tmp, &channel->sc_list) {
 		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
-		vmbus_close_internal(cur_channel);
 		if (cur_channel->rescind) {
+			wait_for_completion(&cur_channel->rescind_event);
+			mutex_lock(&vmbus_connection.channel_mutex);
+			vmbus_close_internal(cur_channel);
 			hv_process_channel_removal(
 					   cur_channel->offermsg.child_relid);
+		} else {
+			mutex_lock(&vmbus_connection.channel_mutex);
+			vmbus_close_internal(cur_channel);
 		}
+		mutex_unlock(&vmbus_connection.channel_mutex);
 	}
 	/*
 	 * Now close the primary.
 	 */
+	mutex_lock(&vmbus_connection.channel_mutex);
 	vmbus_close_internal(channel);
 	mutex_unlock(&vmbus_connection.channel_mutex);
 }
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -333,6 +333,7 @@ static struct vmbus_channel *alloc_channel(void)
 		return NULL;
 
 	spin_lock_init(&channel->lock);
+	init_completion(&channel->rescind_event);
 
 	INIT_LIST_HEAD(&channel->sc_list);
 	INIT_LIST_HEAD(&channel->percpu_list);
@@ -898,6 +899,7 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 	/*
 	 * Now wait for offer handling to complete.
 	 */
+	vmbus_rescind_cleanup(channel);
 	while (READ_ONCE(channel->probe_done) == false) {
 		/*
 		 * We wait here until any channel offer is currently
@@ -913,7 +915,6 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 	if (channel->device_obj) {
 		if (channel->chn_rescind_callback) {
 			channel->chn_rescind_callback(channel);
-			vmbus_rescind_cleanup(channel);
 			return;
 		}
 		/*
@@ -922,7 +923,6 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 		 */
 		dev = get_device(&channel->device_obj->device);
 		if (dev) {
-			vmbus_rescind_cleanup(channel);
 			vmbus_device_unregister(channel->device_obj);
 			put_device(dev);
 		}
@@ -936,13 +936,14 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 		 * 2. Then close the primary channel.
 		 */
 		mutex_lock(&vmbus_connection.channel_mutex);
-		vmbus_rescind_cleanup(channel);
 		if (channel->state == CHANNEL_OPEN_STATE) {
 			/*
 			 * The channel is currently not open;
 			 * it is safe for us to cleanup the channel.
 			 */
 			hv_process_channel_removal(rescind->child_relid);
+		} else {
+			complete(&channel->rescind_event);
 		}
 		mutex_unlock(&vmbus_connection.channel_mutex);
 	}
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -708,6 +708,7 @@ struct vmbus_channel {
 	u8 monitor_bit;
 
 	bool rescind; /* got rescind msg */
+	struct completion rescind_event;
 
 	u32 ringbuffer_gpadlhandle;