[PATCH 4.19 30/48] Drivers: hv: vmbus: Ignore CHANNELMSG_TL_CONNECT_RESULT(23)

Greg Kroah-Hartman
2020-08-10T15:31:37Z

From: Dexuan Cui <decui@microsoft.com>

[ Upstream commit ddc9d357b991838c2d975e8d7e4e9db26f37a7ff ]

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@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 3bf1f9ef8ea25..c83361a8e2033 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -1249,6 +1249,8 @@ 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 },
};

/*
@@ -1260,25 +1262,16 @@ 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 fb22b72fd535a..0699c60188895 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -939,6 +939,10 @@ 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 c43e694fef7dd..35461d49d3aee 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -428,6 +428,8 @@ 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
};

--
2.25.1