Prevent buffer overflow when reading large messages.

https://bugzilla.redhat.com/show_bug.cgi?id=1401603
https://access.redhat.com/security/cve/CVE-2016-9577
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-9577
https://security-tracker.debian.org/tracker/CVE-2016-9577

Patch copied from upstream source repository:

https://cgit.freedesktop.org/spice/spice/commit/?h=0.12&id=5f96b596353d73bdf4bb3cd2de61e48a7fd5b4c3

From 5f96b596353d73bdf4bb3cd2de61e48a7fd5b4c3 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Tue, 29 Nov 2016 16:46:56 +0000
Subject: main-channel: Prevent overflow reading messages from client

diff --git a/server/main_channel.c b/server/main_channel.c
index 0ecc9df..1fc3915 100644
--- a/server/main_channel.c
+++ b/server/main_channel.c
@@ -1026,6 +1026,9 @@ static uint8_t *main_channel_alloc_msg_rcv_buf(RedChannelClient *rcc,
 
     if (type == SPICE_MSGC_MAIN_AGENT_DATA) {
         return reds_get_agent_data_buffer(mcc, size);
+    } else if (size > sizeof(main_chan->recv_buf)) {
+        /* message too large, caller will log a message and close the connection */
+        return NULL;
     } else {
         return main_chan->recv_buf;
     }
-- 
cgit v0.10.2