Bug 1375677

Summary:	Crash when performing VNC websockets handshake
Product:	Red Hat Enterprise Linux 7	Reporter:	Daniel Berrangé <berrange>
Component:	qemu-kvm-rhev	Assignee:	Daniel Berrangé <berrange>
Status:	CLOSED ERRATA	QA Contact:	Guo, Zhiyi <zhguo>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	7.3	CC:	chayang, juzhang, knoel, mrezanin, qzhang, tlavigne, virt-maint
Target Milestone:	rc	Keywords:	Regression
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	qemu-kvm-rhev-2.6.0-26.el7	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-11-07 21:36:01 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Daniel Berrangé 2016-09-13 16:33:01 UTC

Description of problem:
When using VNC with TLS and websockets, QEMU will crash when the client connects

https://bugs.launchpad.net/qemu/+bug/1589923

This is a regression vs 2.4.0 and fixed in

commit bc35d51077b33e68a0ab10a057f352747214223f
Author: Daniel P. Berrange <berrange>
Date:   Tue Jun 7 12:27:51 2016 +0100

    io: remove mistaken call to object_ref on QTask
    
    The QTask struct is just a standalone struct, not a QOM Object,
    so calling object_ref() on it is not appropriate. This results
    in mangling the 'destroy' field in the QTask struct, causing
    the later call to qtask_free() to try to call the function
    at address 0x1, with predictably segfault happy results.
    
    There is in fact no need for ref counting with QTask, as the
    call to qtask_abort() or qtask_complete() will automatically
    free associated memory.
    
    This fixes the crash shown in
    
      https://bugs.launchpad.net/qemu/+bug/1589923
    
    Reviewed-by: Eric Blake <eblake>
    Signed-off-by: Daniel P. Berrange <berrange>



Version-Release number of selected component (if applicable):
qemu-kvm-rhev-2.6.0-22.el7

How reproducible:
Always

Steps to Reproduce:
1. Run QEMU with websockets + TLS eg

  $ qemu-system-x86_64 -vnc 0.0.0.0:1,tls,x509=/etc/pki/qemu,websocket=5701

2. Connect with the noVNC client with TLS enabled

Actual results:
QEMU crashes

Expected results:
Connection completes

Additional info:

Comment 3 Miroslav Rezanina 2016-09-20 12:30:53 UTC

Fix included in qemu-kvm-rhev-2.6.0-26.el7

Comment 5 Daniel Berrangé 2016-09-21 10:48:45 UTC

NB you can actually trigger the crash without TLS too. eg with just

  $QEMU -vnc 127.0.0.1:0,websocket=5902,password


If you are trying to trigger the crash with TLS, then you need to make sure to import the CA certificate used by QEMU into the web browser CA store, otherwise firefox will drop the connection before triggering the crash due to invalid CA.

Comment 6 Guo, Zhiyi 2016-09-21 13:48:15 UTC

Reproduce this issue against qemu-kvm-rhev-2.6.0-25.el7.x86_64.

Steps:
1. boot qemu by: /usr/libexec/qemu-kvm -vnc :1,websocket=5701
2. Download noVNC and lauch websocket server by: ./utils/launch.sh, follow the onVNC prompt, browse http://dhcp-9-154.nay.redhat.com:6080/vnc.html?host=dhcp-9-154.nay.redhat.com&port=5701 from firefox or chrome

Results:
After step 2, qemu crash with backtrace:
#0  0x0000000000000001 in ?? ()
#1  0x00007f96fdc731d3 in qio_task_free (task=0x7f97021675a0) at io/task.c:58
#2  0x00007f96fdc732da in qio_task_complete (task=<optimized out>)
    at io/task.c:145
#3  0x00007f96fdc72fb1 in qio_channel_websock_handshake_send (
    ioc=0x7f9701bdbce0, condition=<optimized out>, user_data=0x7f97021675a0)
    at io/channel-websock.c:289
#4  0x00007f96f4a08d7a in g_main_context_dispatch ()
   from /lib64/libglib-2.0.so.0
#5  0x00007f96fdc119e0 in glib_pollfds_poll () at main-loop.c:213
#6  os_host_main_loop_wait (timeout=<optimized out>) at main-loop.c:258
#7  main_loop_wait (nonblocking=<optimized out>) at main-loop.c:506
#8  0x00007f96fd9df70f in main_loop () at vl.c:1936
#9  main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>)
    at vl.c:4692

Verify against qemu-kvm-rhev-2.6.0-26.el7.x86_64, after step 2, no qemu crash happen, and noVNC connect to websocket of qemu

Comment 9 errata-xmlrpc 2016-11-07 21:36:01 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2673.html