[Qemu-devel] [PATCH 1/1] io/channel-websock: handle continuous reads without any data

[Denis V. Lunev]

From: Edgar Kaziakhmedov <address@hidden>

According to the current implementation of websocket protocol in QEMU,
qio_channel_websock_handshake_io tries to read handshake from the
channel to start communication over tcp socket. But this subroutine
doesn't cover scenario when socket was closed while handshaking. Therefore,
if G_IO_IN is caught and qio_channel_websock_handshake_read returns
zero, error has to be set and connection has to be done.

Such behaviour causes 100% CPU load in main QEMU loop, because main loop
poll continues to receive and handle G_IO_IN events from websocket.

Step to reproduce 100% CPU load:
- start qemu with the simplest configuration
    $ qemu -vnc [::1]:1,websocket=7500
2) open any vnc listener (which doesn't follow websocket protocol)
    $ vncviewer :7500
3) kill listener
4) qemu main thread eats 100% CPU usage

Signed-off-by: Edgar Kaziakhmedov <address@hidden>
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Daniel P. Berrange <address@hidden>
---
 io/channel-websock.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/io/channel-websock.c b/io/channel-websock.c
index 87ebdeb..71f046a 100644
--- a/io/channel-websock.c
+++ b/io/channel-websock.c
@@ -581,9 +581,11 @@ static gboolean 
qio_channel_websock_handshake_io(QIOChannel *ioc,
         return FALSE;
     }
     if (ret == 0) {
-        trace_qio_channel_websock_handshake_pending(ioc, G_IO_IN);
-        /* need more data still */
-        return TRUE;
+        /* If G_IN_IO happened and there is no data to read, close connection 
*/
+        error_setg(&err, "connection was closed");
+        qio_task_set_error(task, err);
+        qio_task_complete(task);
+        return FALSE;
     }
 
     if (err) {
-- 
2.7.4