| Message ID | 20180110153924.17391-1-edgar.kaziakhmedov@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jan 10, 2018 at 06:39:24PM +0300, Edgar Kaziakhmedov wrote: > 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 <edgar.kaziakhmedov@virtuozzo.com> > --- > io/channel-websock.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) Thanks, I have queued this patch. Regards, Daniel
diff --git a/io/channel-websock.c b/io/channel-websock.c index 87ebdebfc0..1152715535 100644 --- a/io/channel-websock.c +++ b/io/channel-websock.c @@ -502,9 +502,12 @@ 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';
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 <edgar.kaziakhmedov@virtuozzo.com> --- io/channel-websock.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) -- 2.11.0