linux-kernel - [PATCH v2] Drivers: hv: vmbus: Ignore CHANNELMSG_TL_CONNECT

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Message-Id: <1579476562-125673-1-git-send-email-decui@microsoft.com>
Date:   Sun, 19 Jan 2020 15:29:22 -0800
From:   Dexuan Cui <decui@...rosoft.com>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com,
        Alexander.Levin@...rosoft.com
Cc:     sunilmut@...rosoft.com, Andrea.Parri@...rosoft.com,
        weh@...rosoft.com, Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v2] Drivers: hv: vmbus: Ignore CHANNELMSG_TL_CONNECT_RESULT(23)

When a Linux hv_sock app tries to connect to a Service GUID on which no
host app is listening, a recent host (RS3+) sends a
CHANNELMSG_TL_CONNECT_RESULT (23) message to Linux and this triggers such
a warning:

unknown msgtype=23
WARNING: CPU: 2 PID: 0 at drivers/hv/vmbus_drv.c:1031 vmbus_on_msg_dpc

Actually Linux can safely ignore the message because the Linux app's
connect() will time out in 2 seconds: see VSOCK_DEFAULT_CONNECT_TIMEOUT
and vsock_stream_connect(). We don't bother to make use of the message
because: 1) it's only supported on recent hosts; 2) a non-trivial effort
is required to use the message in Linux, but the benefit is small.

So, let's not see the warning by silently ignoring the message.

Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---

In v2 (followed Michael Kelley's suggestions):
    Removed the redundant code in vmbus_onmessage()
    Added the new enries into channel_message_table[].

 drivers/hv/channel_mgmt.c | 21 +++++++--------------
 drivers/hv/vmbus_drv.c    |  4 ++++
 include/linux/hyperv.h    |  2 ++
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 8eb167540b4f..0370364169c4 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -1351,6 +1351,8 @@ channel_message_table[CHANNELMSG_COUNT] = {
 	{ CHANNELMSG_19,			0, NULL },
 	{ CHANNELMSG_20,			0, NULL },
 	{ CHANNELMSG_TL_CONNECT_REQUEST,	0, NULL },
+	{ CHANNELMSG_22,			0, NULL },
+	{ CHANNELMSG_TL_CONNECT_RESULT,		0, NULL },
 };
 
 /*
@@ -1362,25 +1364,16 @@ void vmbus_onmessage(void *context)
 {
 	struct hv_message *msg = context;
 	struct vmbus_channel_message_header *hdr;
-	int size;
 
 	hdr = (struct vmbus_channel_message_header *)msg->u.payload;
-	size = msg->header.payload_size;
 
 	trace_vmbus_on_message(hdr);
 
-	if (hdr->msgtype >= CHANNELMSG_COUNT) {
-		pr_err("Received invalid channel message type %d size %d\n",
-			   hdr->msgtype, size);
-		print_hex_dump_bytes("", DUMP_PREFIX_NONE,
-				     (unsigned char *)msg->u.payload, size);
-		return;
-	}
-
-	if (channel_message_table[hdr->msgtype].message_handler)
-		channel_message_table[hdr->msgtype].message_handler(hdr);
-	else
-		pr_err("Unhandled channel message type %d\n", hdr->msgtype);
+	/*
+	 * vmbus_on_msg_dpc() makes sure the hdr->msgtype here can not go
+	 * out of bound and the message_handler pointer can not be NULL.
+	 */
+	channel_message_table[hdr->msgtype].message_handler(hdr);
 }
 
 /*
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 4ef5a66df680..029378c27421 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1033,6 +1033,10 @@ void vmbus_on_msg_dpc(unsigned long data)
 	}
 
 	entry = &channel_message_table[hdr->msgtype];
+
+	if (!entry->message_handler)
+		goto msg_handled;
+
 	if (entry->handler_type	== VMHT_BLOCKING) {
 		ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
 		if (ctx == NULL)
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 8fa0938f9aee..692c89ccf5df 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -425,6 +425,8 @@ enum vmbus_channel_message_type {
 	CHANNELMSG_19				= 19,
 	CHANNELMSG_20				= 20,
 	CHANNELMSG_TL_CONNECT_REQUEST		= 21,
+	CHANNELMSG_22				= 22,
+	CHANNELMSG_TL_CONNECT_RESULT		= 23,
 	CHANNELMSG_COUNT
 };
 
-- 
2.19.1