Fixes a potential buffer overflow in the protocol handling.

https://bugzilla.redhat.com/show_bug.cgi?id=1399566
https://access.redhat.com/security/cve/CVE-2016-9578
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-9578
https://security-tracker.debian.org/tracker/CVE-2016-9578

Patch copied from upstream source repository:

https://cgit.freedesktop.org/spice/spice/commit/?h=0.12&id=f66dc643635518e53dfbe5262f814a64eec54e4a

From f66dc643635518e53dfbe5262f814a64eec54e4a Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Tue, 13 Dec 2016 14:40:10 +0000
Subject: Prevent integer overflows in capability checks

diff --git a/server/reds.c b/server/reds.c
index 86a33d5..9150454 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -2110,6 +2110,14 @@ static void reds_handle_read_link_done(void *opaque)
     link_mess->num_channel_caps = GUINT32_FROM_LE(link_mess->num_channel_caps);
     link_mess->num_common_caps = GUINT32_FROM_LE(link_mess->num_common_caps);
 
+    /* Prevent DoS. Currently we defined only 13 capabilities,
+     * I expect 1024 to be valid for quite a lot time */
+    if (link_mess->num_channel_caps > 1024 || link_mess->num_common_caps > 1024) {
+        reds_send_link_error(link, SPICE_LINK_ERR_INVALID_DATA);
+        reds_link_free(link);
+        return;
+    }
+
     num_caps = link_mess->num_common_caps + link_mess->num_channel_caps;
     caps = (uint32_t *)((uint8_t *)link_mess + link_mess->caps_offset);
 
-- 
cgit v0.10.2