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Date:   Fri, 8 Feb 2019 05:01:12 -0500
From:   Kimberly Brown <kimbrownkd@gmail.com>
To:     Michael Kelley <mikelley@microsoft.com>,
        Long Li <longli@microsoft.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Dexuan Cui <decui@microsoft.com>
Cc:     "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        devel@linuxdriverproject.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] Drivers: hv: vmbus: Display nothing in sysfs if
 monitor_allocated not set
Message-ID: <52d58fe5805f2ba2405c9091b4c86033d434d2b9.1549619051.git.kimbrownkd@gmail.com>
References: <cover.1549619051.git.kimbrownkd@gmail.com>
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If monitor pages are not allocated to a channel, the channel does not
have a valid monitor id or valid monitor page data. In these cases, some
of the "_show" functions display incorrect data. The "_show" functions
that display monitor page data access and display data that is beyond
the bounds of the hv_monitor_page array fields, which is obviously
incorrect. The "_show" functions that display the monitor id display an
invalid monitor id.

The "channel->offermsg.monitor_allocated" value can be used to determine
whether monitor pages have been allocated to a channel. In the affected
"_show" functions, verify that "channel->offermsg.monitor_allocated" is
set before accessing the monitor id or the monitor_page data. If
"channel->offermsg.monitor_allocated" is not set, display nothing.

Signed-off-by: Kimberly Brown <kimbrownkd@gmail.com>
---
 Documentation/ABI/stable/sysfs-bus-vmbus |  9 ++++--
 drivers/hv/vmbus_drv.c                   | 37 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/Documentation/ABI/stable/sysfs-bus-vmbus b/Documentation/ABI/stable/sysfs-bus-vmbus
index 3fed8fdb873d..af52be4ffc5d 100644
--- a/Documentation/ABI/stable/sysfs-bus-vmbus
+++ b/Documentation/ABI/stable/sysfs-bus-vmbus
@@ -81,7 +81,8 @@ What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>/latency
 Date:		September. 2017
 KernelVersion:	4.14
 Contact:	Stephen Hemminger <sthemmin@microsoft.com>
-Description:	Channel signaling latency
+Description:	Channel signaling latency. If monitor pages are not allocated
+		to the channel, nothing is displayed.
 Users:		Debugging tools
 
 What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>/out_mask
@@ -95,7 +96,8 @@ What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>/pending
 Date:		September. 2017
 KernelVersion:	4.14
 Contact:	Stephen Hemminger <sthemmin@microsoft.com>
-Description:	Channel interrupt pending state
+Description:	Channel interrupt pending state. If monitor pages are not
+		allocated to the channel, nothing is displayed.
 Users:		Debugging tools
 
 What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>/read_avail
@@ -137,7 +139,8 @@ What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>/monitor_id
 Date:		January. 2018
 KernelVersion:	4.16
 Contact:	Stephen Hemminger <sthemmin@microsoft.com>
-Description:	Monitor bit associated with channel
+Description:	Monitor bit associated with channel. If monitor pages are not
+		allocated to the channel, nothing is displayed.
 Users:		Debugging tools and userspace drivers
 
 What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>/ring
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index f2a79f5129d7..c88a3623be56 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -171,6 +171,10 @@ static ssize_t monitor_id_show(struct device *dev,
 
 	if (!hv_dev->channel)
 		return -ENODEV;
+
+	if (!hv_dev->channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n", hv_dev->channel->offermsg.monitorid);
 }
 static DEVICE_ATTR_RO(monitor_id);
@@ -232,6 +236,10 @@ static ssize_t server_monitor_pending_show(struct device *dev,
 
 	if (!hv_dev->channel)
 		return -ENODEV;
+
+	if (!hv_dev->channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_pending(hv_dev->channel,
 				       vmbus_connection.monitor_pages[0]));
@@ -246,6 +254,10 @@ static ssize_t client_monitor_pending_show(struct device *dev,
 
 	if (!hv_dev->channel)
 		return -ENODEV;
+
+	if (!hv_dev->channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_pending(hv_dev->channel,
 				       vmbus_connection.monitor_pages[1]));
@@ -260,6 +272,10 @@ static ssize_t server_monitor_latency_show(struct device *dev,
 
 	if (!hv_dev->channel)
 		return -ENODEV;
+
+	if (!hv_dev->channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_latency(hv_dev->channel,
 				       vmbus_connection.monitor_pages[0]));
@@ -274,6 +290,10 @@ static ssize_t client_monitor_latency_show(struct device *dev,
 
 	if (!hv_dev->channel)
 		return -ENODEV;
+
+	if (!hv_dev->channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_latency(hv_dev->channel,
 				       vmbus_connection.monitor_pages[1]));
@@ -288,6 +308,10 @@ static ssize_t server_monitor_conn_id_show(struct device *dev,
 
 	if (!hv_dev->channel)
 		return -ENODEV;
+
+	if (!hv_dev->channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_conn_id(hv_dev->channel,
 				       vmbus_connection.monitor_pages[0]));
@@ -302,6 +326,10 @@ static ssize_t client_monitor_conn_id_show(struct device *dev,
 
 	if (!hv_dev->channel)
 		return -ENODEV;
+
+	if (!hv_dev->channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_conn_id(hv_dev->channel,
 				       vmbus_connection.monitor_pages[1]));
@@ -1469,6 +1497,9 @@ static VMBUS_CHAN_ATTR(cpu, S_IRUGO, show_target_cpu, NULL);
 static ssize_t channel_pending_show(const struct vmbus_channel *channel,
 				    char *buf)
 {
+	if (!channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_pending(channel,
 				       vmbus_connection.monitor_pages[1]));
@@ -1478,6 +1509,9 @@ static VMBUS_CHAN_ATTR(pending, S_IRUGO, channel_pending_show, NULL);
 static ssize_t channel_latency_show(const struct vmbus_channel *channel,
 				    char *buf)
 {
+	if (!channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%d\n",
 		       channel_latency(channel,
 				       vmbus_connection.monitor_pages[1]));
@@ -1499,6 +1533,9 @@ static VMBUS_CHAN_ATTR(events, S_IRUGO, channel_events_show, NULL);
 static ssize_t subchannel_monitor_id_show(const struct vmbus_channel *channel,
 					  char *buf)
 {
+	if (!channel->offermsg.monitor_allocated)
+		return sprintf(buf, "\n");
+
 	return sprintf(buf, "%u\n", channel->offermsg.monitorid);
 }
 static VMBUS_CHAN_ATTR(monitor_id, S_IRUGO, subchannel_monitor_id_show, NULL);
-- 
2.17.1