Matthias Maier <tamiko@gentoo.org>

 - Ported to 0.13.3


From fbbcdad773e2791cfb988f4748faa41943551ca6 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Mon, 15 May 2017 15:57:28 +0100
Subject: [PATCH 3/3] reds: Avoid buffer overflows handling monitor
 configuration

It was also possible for a malicious client to set
VDAgentMonitorsConfig::num_of_monitors to a number larger
than the actual size of VDAgentMOnitorsConfig::monitors.
This would lead to buffer overflows, which could allow the guest to
read part of the host memory. This might cause write overflows in the
host as well, but controlling the content of such buffers seems
complicated.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
---

diff --git a/server/reds.c b/server/reds.c
index ec89105..fd1457f 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -1084,6 +1084,7 @@ static void reds_on_main_agent_monitors_config(RedsState *reds,
     VDAgentMessage *msg_header;
     VDAgentMonitorsConfig *monitors_config;
     RedsClientMonitorsConfig *cmc = &reds->client_monitors_config;
+    uint32_t max_monitors;
 
     // limit size of message sent by the client as this can cause a DoS through
     // memory exhaustion, or potentially some integer overflows
@@ -1113,6 +1114,12 @@ static void reds_on_main_agent_monitors_config(RedsState *reds,
         goto overflow;
     }
     monitors_config = (VDAgentMonitorsConfig *)(cmc->buffer + sizeof(*msg_header));
+    // limit the monitor number to avoid buffer overflows
+    max_monitors = (msg_header->size - sizeof(VDAgentMonitorsConfig)) /
+                   sizeof(VDAgentMonConfig);
+    if (monitors_config->num_of_monitors > max_monitors) {
+        goto overflow;
+    }
     spice_debug("%s: %d", __func__, monitors_config->num_of_monitors);
     reds_client_monitors_config(reds, monitors_config);
     reds_client_monitors_config_cleanup(reds);