vnc: fix use-after-free

When vnc_client_read() return value is -1
vs is not valid any more.

Fixes: d49b87f0d1e0520443a990fc610d0f02bc63c556
Reported-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180420084820.3873-1-kraxel@redhat.com

1 files changed, 3 insertions, 2 deletions

diff --git a/ui/vnc.c b/ui/vnc.c
index e164eb798c..5526e54f48 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -1539,13 +1539,14 @@ gboolean vnc_client_io(QIOChannel *ioc G_GNUC_UNUSED,
     VncState *vs = opaque;
     if (condition & G_IO_IN) {
         if (vnc_client_read(vs) < 0) {
-            goto end;
+            /* vs is free()ed here */
+            return TRUE;
         }
     }
     if (condition & G_IO_OUT) {
         vnc_client_write(vs);
     }
-end:
+
     if (vs->disconnecting) {
         if (vs->ioc_tag != 0) {
             g_source_remove(vs->ioc_tag);