[Qemu-devel] [Bug 1586194] [NEW] VNC reverse broken in qemu 2.6.0

[Andreas Hofmeister]

Public bug reported:

Hi all,

I recently tried to upgrade from Qemu 2.4.1 to 2.6.0, but found some
problems with VNC reverse connections.

1) In "-vnc 172.16.1.3:5902,reverse" used to mean "connect to port 5902"
   That seems to have changed changed since 2.4.1, the thing after the IP 
address is now interpreted
   as a display number. If that change was intentional, the man-page needs to 
be fixed.

2) After subtracting 5900 from that port number (-vnc
172.16.1.3:2,reverse), I ran into a segfault.

---8<---   
Program received signal SIGSEGV, Segmentation fault.
qio_channel_socket_get_local_address (ioc=0x0, address@hidden) at 
io/channel-socket.c:33
33          return socket_sockaddr_to_address(&ioc->localAddr,
(gdb) bt
#0  qio_channel_socket_get_local_address (ioc=0x0, address@hidden) at 
io/channel-socket.c:33
#1  0x000055555594c0f5 in vnc_init_basic_info_from_server_addr 
(errp=0x7fffffffe118, info=0x555558f35990, 
    ioc=<optimized out>) at ui/vnc.c:146
#2  vnc_server_info_get (vd=0x7fffecc4b010) at ui/vnc.c:223
#3  0x000055555595192a in vnc_qmp_event (vs=0x555558f41f30, vs=0x555558f41f30, 
event=QAPI_EVENT_VNC_CONNECTED)
    at ui/vnc.c:279
#4  vnc_connect (address@hidden, address@hidden, address@hidden, 
    address@hidden) at ui/vnc.c:2994
#5  0x00005555559520d8 in vnc_display_open (address@hidden "default", 
address@hidden)
    at ui/vnc.c:3773
#6  0x0000555555952fd3 in vnc_init_func (opaque=<optimized out>, 
opts=<optimized out>, errp=<optimized out>)
    at ui/vnc.c:3868
#7  0x0000555555a011da in qemu_opts_foreach (list=<optimized out>, 
func=0x555555952fa0 <vnc_init_func>, opaque=0x0, 
    errp=0x0) at util/qemu-option.c:1116
#8  0x00005555556dcfbe in main (argc=<optimized out>, argv=<optimized out>, 
envp=<optimized out>) at vl.c:4592
--->8---

A git bisect shows that this happens since

---8<---
commit 98481bfcd661daa3c160cc87a297b0e60a307788
Author: Eric Blake <address@hidden>
Date:   Mon Oct 26 16:34:45 2015 -0600

    vnc: Hoist allocation of VncBasicInfo to callers
--->8--- 

TIA
  Andi

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1586194

Title:
  VNC reverse broken in qemu 2.6.0

Status in QEMU:
  New

Bug description:
  Hi all,

  I recently tried to upgrade from Qemu 2.4.1 to 2.6.0, but found some
  problems with VNC reverse connections.

  1) In "-vnc 172.16.1.3:5902,reverse" used to mean "connect to port 5902"
     That seems to have changed changed since 2.4.1, the thing after the IP 
address is now interpreted
     as a display number. If that change was intentional, the man-page needs to 
be fixed.

  2) After subtracting 5900 from that port number (-vnc
  172.16.1.3:2,reverse), I ran into a segfault.

  ---8<---   
  Program received signal SIGSEGV, Segmentation fault.
  qio_channel_socket_get_local_address (ioc=0x0, address@hidden) at 
io/channel-socket.c:33
  33          return socket_sockaddr_to_address(&ioc->localAddr,
  (gdb) bt
  #0  qio_channel_socket_get_local_address (ioc=0x0, address@hidden) at 
io/channel-socket.c:33
  #1  0x000055555594c0f5 in vnc_init_basic_info_from_server_addr 
(errp=0x7fffffffe118, info=0x555558f35990, 
      ioc=<optimized out>) at ui/vnc.c:146
  #2  vnc_server_info_get (vd=0x7fffecc4b010) at ui/vnc.c:223
  #3  0x000055555595192a in vnc_qmp_event (vs=0x555558f41f30, 
vs=0x555558f41f30, event=QAPI_EVENT_VNC_CONNECTED)
      at ui/vnc.c:279
  #4  vnc_connect (address@hidden, address@hidden, address@hidden, 
      address@hidden) at ui/vnc.c:2994
  #5  0x00005555559520d8 in vnc_display_open (address@hidden "default", 
address@hidden)
      at ui/vnc.c:3773
  #6  0x0000555555952fd3 in vnc_init_func (opaque=<optimized out>, 
opts=<optimized out>, errp=<optimized out>)
      at ui/vnc.c:3868
  #7  0x0000555555a011da in qemu_opts_foreach (list=<optimized out>, 
func=0x555555952fa0 <vnc_init_func>, opaque=0x0, 
      errp=0x0) at util/qemu-option.c:1116
  #8  0x00005555556dcfbe in main (argc=<optimized out>, argv=<optimized out>, 
envp=<optimized out>) at vl.c:4592
  --->8---

  A git bisect shows that this happens since

  ---8<---
  commit 98481bfcd661daa3c160cc87a297b0e60a307788
  Author: Eric Blake <address@hidden>
  Date:   Mon Oct 26 16:34:45 2015 -0600

      vnc: Hoist allocation of VncBasicInfo to callers
  --->8--- 

  TIA
    Andi

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