[Qemu-devel] Guest crash when VNC connection is established with password (QEMU 2.5.1.1)

[John Y.]

(Sorry for repost,  I had asked in qemu-stable, but someone told me that I
should send to qemu-devel.)

After I updated my Centos to 7.5.1804, my virtual machine crashed when I
connected with vnc password.

*1. My problem：*

Here  what I tested:
(1).  started a guest with : qemu-system-x86_64 -m 2048 test.img -vnc
0.0.0.0:3 <http://0.0.0.0:7>,password -monitor stdio
(2). change password to 1234567.
(3). connected with VncViewer

Here was the output:

# qemu-system-x86_64 -m 2048 test.img -vnc 0.0.0.0:3,password -monitor stdio
> QEMU 2.5.1.1 monitor - type 'help' for more information
> (qemu) change vnc password 12345678
> (qemu) Segmentation fault
>

I  debugged with gdb and got:

> (qemu) change vnc password 12345678
> (qemu)
> Program received signal SIGSEGV, Segmentation fault.
> 0x00007ffff528cc80 in pthread_mutex_lock () from /lib64/libpthread.so.0
> (gdb) bt
> #0  0x00007ffff528cc80 in pthread_mutex_lock () from /lib64/libpthread.so.0
> #1  0x0000555555a97f4a in qemu_mutex_lock (mutex=0x0) at
> util/qemu-thread-posix.c:73
> #2  0x0000555555a5cce3 in qcrypto_gcrypt_mutex_lock (priv=0x7ffff6e90ca0)
> at crypto/init.c:97
> #3  0x00007ffff6c217c5 in mutex_init () from /lib64/libgcrypt.so.11
> #4  0x00007ffff6c21baa in _gcry_ath_mutex_lock () from
> /lib64/libgcrypt.so.11
> #5  0x00007ffff6c5ad20 in lock_pool () from /lib64/libgcrypt.so.11
> #6  0x00007ffff6c5be2e in _gcry_rngcsprng_fast_poll () from
> /lib64/libgcrypt.so.11
> #7  0x00007ffff6c23d4d in _gcry_cipher_open () from /lib64/libgcrypt.so.11
> #8  0x0000555555a60251 in qcrypto_cipher_new
> (alg=QCRYPTO_CIPHER_ALG_DES_RFB, mode=QCRYPTO_CIPHER_MODE_ECB,
> key=0x7fffffffdf30 "12345678\020", nkey=8, errp=0x7fffffffdf08) at
> ./crypto/cipher-gcrypt.c:97
> #9  0x00005555559d8912 in protocol_client_auth_vnc (vs=0x5555565b5660,
> data=0x555557a6c0a0 "\036\352\"s٘\373\345<ܯ\210L\b;$\220\300\246WUU",
> len=16) at ui/vnc.c:2551
> #10 0x00005555559d60b5 in vnc_client_read (opaque=0x5555565b5660) at
> ui/vnc.c:1564
> #11 0x0000555555a046a7 in aio_dispatch (ctx=0x555556508790) at
> aio-posix.c:326
> #12 0x00005555559f4166 in aio_ctx_dispatch (source=0x555556508790,
> callback=0x0, user_data=0x0) at async.c:231
> #13 0x00007ffff5f10969 in g_main_context_dispatch () from
> /lib64/libglib-2.0.so.0
> #14 0x0000555555a026e7 in glib_pollfds_poll () at main-loop.c:211
> #15 0x0000555555a027c4 in os_host_main_loop_wait (timeout=54752182) at
> main-loop.c:256
> #16 0x0000555555a02874 in main_loop_wait (nonblocking=0) at main-loop.c:504
> #17 0x00005555558251c1 in main_loop () at vl.c:1923
> #18 0x000055555582cbe5 in main (argc=8, argv=0x7fffffffe558,
> envp=0x7fffffffe5a0) at vl.c:4699
>


*2.  Other Infomation*
(1).  Version of qemu:
QEMU emulator version 2.5.1.1, Copyright (c) 2003-2008 Fabrice Bellard

(2).  kernel and os：
kernel : 4.16.3-1.el7.elrepo.x86_64
os: CentOS Linux release 7.5.1804 (Core)

(3).  I had try /usr/libexec/qemu-kvm(qemu-kvm-1.5.3-156.el7_5.5)  and qemu
2.11, both of them worked fine.

(4).  Has no problem witout vnc password.

(5). I update my host with yum update.

(6).  Everything work find before update.

*3.  My Question*
For some reasons I have to use qemu 2.5.11 and update Centos.
(1) What causes this problem and how can I solve it ?

Looking forward to your reply.

Regards,
John