linux-kernel - [PATCH 4.9 112/153] Drivers: hv: vmbus: Fix a rescind handling bug

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Date:   Fri, 10 Mar 2017 10:09:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 4.9 112/153] Drivers: hv: vmbus: Fix a rescind handling bug

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: K. Y. Srinivasan <kys@...rosoft.com>

commit ccb61f8a99e6c29df4fb96a65dad4fad740d5be9 upstream.

The host can rescind a channel that has been offered to the
guest and once the channel is rescinded, the host does not
respond to any requests on that channel. Deal with the case where
the guest may be blocked waiting for a response from the host.

Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/hv/channel.c      |   18 ++++++++++++++++++
 drivers/hv/channel_mgmt.c |   25 +++++++++++++++++++++++++
 include/linux/hyperv.h    |    1 +
 3 files changed, 44 insertions(+)

--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -157,6 +157,7 @@ int vmbus_open(struct vmbus_channel *new
 	}
 
 	init_completion(&open_info->waitevent);
+	open_info->waiting_channel = newchannel;
 
 	open_msg = (struct vmbus_channel_open_channel *)open_info->msg;
 	open_msg->header.msgtype = CHANNELMSG_OPENCHANNEL;
@@ -194,6 +195,11 @@ int vmbus_open(struct vmbus_channel *new
 	list_del(&open_info->msglistentry);
 	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 
+	if (newchannel->rescind) {
+		err = -ENODEV;
+		goto error_free_gpadl;
+	}
+
 	if (open_info->response.open_result.status) {
 		err = -EAGAIN;
 		goto error_free_gpadl;
@@ -405,6 +411,7 @@ int vmbus_establish_gpadl(struct vmbus_c
 		return ret;
 
 	init_completion(&msginfo->waitevent);
+	msginfo->waiting_channel = channel;
 
 	gpadlmsg = (struct vmbus_channel_gpadl_header *)msginfo->msg;
 	gpadlmsg->header.msgtype = CHANNELMSG_GPADL_HEADER;
@@ -441,6 +448,11 @@ int vmbus_establish_gpadl(struct vmbus_c
 	}
 	wait_for_completion(&msginfo->waitevent);
 
+	if (channel->rescind) {
+		ret = -ENODEV;
+		goto cleanup;
+	}
+
 	/* At this point, we received the gpadl created msg */
 	*gpadl_handle = gpadlmsg->gpadl;
 
@@ -474,6 +486,7 @@ int vmbus_teardown_gpadl(struct vmbus_ch
 		return -ENOMEM;
 
 	init_completion(&info->waitevent);
+	info->waiting_channel = channel;
 
 	msg = (struct vmbus_channel_gpadl_teardown *)info->msg;
 
@@ -493,6 +506,11 @@ int vmbus_teardown_gpadl(struct vmbus_ch
 
 	wait_for_completion(&info->waitevent);
 
+	if (channel->rescind) {
+		ret = -ENODEV;
+		goto post_msg_err;
+	}
+
 post_msg_err:
 	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 	list_del(&info->msglistentry);
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -147,6 +147,29 @@ static const struct {
 	{ HV_RDV_GUID	},
 };
 
+/*
+ * The rescinded channel may be blocked waiting for a response from the host;
+ * take care of that.
+ */
+static void vmbus_rescind_cleanup(struct vmbus_channel *channel)
+{
+	struct vmbus_channel_msginfo *msginfo;
+	unsigned long flags;
+
+
+	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+
+	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
+				msglistentry) {
+
+		if (msginfo->waiting_channel == channel) {
+			complete(&msginfo->waitevent);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+}
+
 static bool is_unsupported_vmbus_devs(const uuid_le *guid)
 {
 	int i;
@@ -825,6 +848,8 @@ static void vmbus_onoffer_rescind(struct
 	channel->rescind = true;
 	spin_unlock_irqrestore(&channel->lock, flags);
 
+	vmbus_rescind_cleanup(channel);
+
 	if (channel->device_obj) {
 		if (channel->chn_rescind_callback) {
 			channel->chn_rescind_callback(channel);
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -641,6 +641,7 @@ struct vmbus_channel_msginfo {
 
 	/* Synchronize the request/response if needed */
 	struct completion  waitevent;
+	struct vmbus_channel *waiting_channel;
 	union {
 		struct vmbus_channel_version_supported version_supported;
 		struct vmbus_channel_open_result open_result;