[gtk-vnc] vnc_connection_start_tls: set tls_session to NULL after deinit

[Daniel P. Berrange <dberrange src gnome org>]

commit 7879ae9c747b4e95bb3850c4e67ca57d3ded82e3
Author: Ján Tomko <jtomko redhat com>
Date:   Fri Jan 11 16:34:31 2019 +0100

    vnc_connection_start_tls: set tls_session to NULL after deinit
    
    Avoid a double free in case of a failure, e.g. when vnc_connection_tls_initialize_cert_cred
    fails to read the certificate:
    
    ==1154== Invalid read of size 4
    ==1154==    at 0x60870FB: gnutls_bye (record.c:288)
    ==1154==    by 0x4A46B73: vnc_connection_close (vncconnection.c:5120)
    ==1154==    by 0x4A4E6CA: vnc_connection_coroutine (vncconnection.c:5650)
    ==1154==    by 0x4A51BCE: coroutine_trampoline (coroutine_ucontext.c:55)
    ==1154==    by 0x5BD81FF: ??? (in /usr/lib64/libc-2.28.so)
    ==1154==    by 0x175DB277: ???
    ==1154==  Address 0x1847fcf0 is 384 bytes inside a block of size 6,496 free'd
    ==1154==    at 0x4839A0C: free (vg_replace_malloc.c:540)
    ==1154==    by 0x4A4B019: vnc_connection_start_tls (vncconnection.c:4466)
    ==1154==    by 0x4A4CBE8: vnc_connection_perform_auth_vencrypt (vncconnection.c:4708)
    ==1154==    by 0x4A4CBE8: vnc_connection_perform_auth (vncconnection.c:4818)
    ==1154==    by 0x4A4CBE8: vnc_connection_initialize (vncconnection.c:5415)
    ==1154==    by 0x4A4E50F: vnc_connection_coroutine (vncconnection.c:5639)
    ==1154==    by 0x4A51BCE: coroutine_trampoline (coroutine_ucontext.c:55)
    ==1154==    by 0x5BD81FF: ??? (in /usr/lib64/libc-2.28.so)
    ==1154==    by 0x175DB277: ???
    ==1154==  Block was alloc'd at
    ==1154==    at 0x483AB1A: calloc (vg_replace_malloc.c:762)
    ==1154==    by 0x60B6FDE: gnutls_init (state.c:465)
    ==1154==    by 0x4A4AB28: vnc_connection_start_tls (vncconnection.c:4434)
    ==1154==    by 0x4A4CBE8: vnc_connection_perform_auth_vencrypt (vncconnection.c:4708)
    ==1154==    by 0x4A4CBE8: vnc_connection_perform_auth (vncconnection.c:4818)
    ==1154==    by 0x4A4CBE8: vnc_connection_initialize (vncconnection.c:5415)
    ==1154==    by 0x4A4E50F: vnc_connection_coroutine (vncconnection.c:5639)
    ==1154==    by 0x4A51BCE: coroutine_trampoline (coroutine_ucontext.c:55)
    ==1154==    by 0x5BD81FF: ??? (in /usr/lib64/libc-2.28.so)
    ==1154==    by 0x175DB277: ???
    
    Signed-off-by: Ján Tomko <jtomko redhat com>

 src/vncconnection.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/vncconnection.c b/src/vncconnection.c
index 9ca8c32..ffecf02 100644
--- a/src/vncconnection.c
+++ b/src/vncconnection.c
@@ -4508,6 +4508,7 @@ static gboolean vnc_connection_start_tls(VncConnection *conn, int anonTLS)
 
  deinit:
     gnutls_deinit(priv->tls_session);
+    priv->tls_session = NULL;
     return FALSE;
 }