[PATCH] io: remove io watch if TLS channel is closed during handshake

["Daniel P. Berrangé" <berrange@redhat.com>]

The TLS handshake make take some time to complete, during which time an
I/O watch might be registered with the main loop. If the owner of the
I/O channel invokes qio_channel_close() while the handshake is waiting
to continue the I/O watch must be removed. Failing to remove it will
later trigger the completion callback which the owner is not expecting
to receive. In the case of the VNC server, this results in a SEGV as
vnc_disconnect_start() tries to shutdown a client connection that is
already gone / NULL.

CVE-2023-3354
Reported-by: jiangyegen <jiangyegen@huawei.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/io/channel-tls.h |  1 +
 io/channel-tls.c         | 18 ++++++++++++------
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/io/channel-tls.h b/include/io/channel-tls.h
index 5672479e9e..26c67f17e2 100644
--- a/include/io/channel-tls.h
+++ b/include/io/channel-tls.h
@@ -48,6 +48,7 @@ struct QIOChannelTLS {
     QIOChannel *master;
     QCryptoTLSSession *session;
     QIOChannelShutdown shutdown;
+    guint hs_ioc_tag;
 };
 
 /**
diff --git a/io/channel-tls.c b/io/channel-tls.c
index 9805dd0a3f..e327e6a5c2 100644
--- a/io/channel-tls.c
+++ b/io/channel-tls.c
@@ -198,12 +198,13 @@ static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
         }
 
         trace_qio_channel_tls_handshake_pending(ioc, status);
-        qio_channel_add_watch_full(ioc->master,
-                                   condition,
-                                   qio_channel_tls_handshake_io,
-                                   data,
-                                   NULL,
-                                   context);
+        ioc->hs_ioc_tag =
+            qio_channel_add_watch_full(ioc->master,
+                                       condition,
+                                       qio_channel_tls_handshake_io,
+                                       data,
+                                       NULL,
+                                       context);
     }
 }
 
@@ -218,6 +219,7 @@ static gboolean qio_channel_tls_handshake_io(QIOChannel *ioc,
     QIOChannelTLS *tioc = QIO_CHANNEL_TLS(
         qio_task_get_source(task));
 
+    tioc->hs_ioc_tag = 0;
     g_free(data);
     qio_channel_tls_handshake_task(tioc, task, context);
 
@@ -378,6 +380,10 @@ static int qio_channel_tls_close(QIOChannel *ioc,
 {
     QIOChannelTLS *tioc = QIO_CHANNEL_TLS(ioc);
 
+    if (tioc->hs_ioc_tag) {
+        g_source_remove(tioc->hs_ioc_tag);
+    }
+
     return qio_channel_close(tioc->master, errp);
 }
 
-- 
2.41.0