Commit a46ded1d authored by Edgar Kaziakhmedov's avatar Edgar Kaziakhmedov Committed by Daniel P. Berrangé
Browse files

io/channel-websock: handle continuous reads without any data 



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 socket. But this approach
doesn't cover scenario when socket was closed while handshaking.
Therefore, if G_IO_IN is caught and qio_channel_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:
1) 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

Signed-off-by: default avatarEdgar Kaziakhmedov <edgar.kaziakhmedov@virtuozzo.com>
Signed-off-by: default avatarDaniel P. Berrange <berrange@redhat.com>
parent 28bb0a59

io/channel-websock.c

+5 −2
Original line number Diff line number Diff line
@@ -499,9 +499,12 @@ static int qio_channel_websock_handshake_read(QIOChannelWebsock *ioc, 
            error_setg(errp,

                       "End of headers not found in first 4096 bytes");

            return 1;

        } else {

            return 0;

        } else if (ret == 0) {

            error_setg(errp,

                       "End of headers not found before connection closed");

            return -1;

        }

        return 0;

    }

    *handshake_end = '\0';