[Qemu-devel] [PATCH] vnc: clear vs->tlscreds after unparenting it

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

This pointer should be cleared in vnc_display_close()
otherwise a use-after-free can happen when when using the
old style 'x509' and 'tls' options rather than a persistent
tls-creds -object, by issuing monitor commands to change
the vnc server like so:

Start with: -vnc unix:test.socket,x509,tls
Then use the following monitor command:
  change vnc unix:test.socket

After this the pointer is still set but invalid and a crash
can be triggered for instance by issuing the same command a
second time which will try to object_unparent() the same
pointer again.
---
 ui/vnc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ui/vnc.c b/ui/vnc.c
index 09756cd..35843b5 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -3134,6 +3134,7 @@ static void vnc_display_close(VncDisplay *vs)
     vs->subauth = VNC_AUTH_INVALID;
     if (vs->tlscreds) {
         object_unparent(OBJECT(vs->tlscreds));
+        vs->tlscreds = NULL;
     }
     g_free(vs->tlsaclname);
     vs->tlsaclname = NULL;
-- 
2.1.4