From a46ded1de5cf0edd6c780e071ddafb92601070b5 Mon Sep 17 00:00:00 2001 From: Edgar Kaziakhmedov Date: Wed, 10 Jan 2018 18:39:24 +0300 Subject: [PATCH] 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: Edgar Kaziakhmedov Signed-off-by: Daniel P. Berrange --- io/channel-websock.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/io/channel-websock.c b/io/channel-websock.c index 7fd6bb68ba..ec48a305f0 100644 --- a/io/channel-websock.c +++ b/io/channel-websock.c @@ -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';