main-channel: Prevent overflow reading messages from client

Caller is supposed the function return a buffer able to store
size bytes.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Christophe Fergeau <cfergeau@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/server/main_channel.c b/server/main_channel.c
index 0ecc9df8..1fc39155 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;
     }