socket: ignore packet if FIONREAD returns zero

zero size is reported for corrupt packets. recvmsg() later could
nevertheless get data from a good packet that followed the bad one.
So get out early to avoid hitting an assertion.

diff --git a/avahi-core/socket.c b/avahi-core/socket.c
index 4146d5ad593e5d3d05dc8265192a147c539f390f..f9b90a2adcad72a276bce4072d2604e6fcec4f03 100644 (file)
--- a/avahi-core/socket.c
+++ b/avahi-core/socket.c
@@ -652,6 +652,10 @@ AvahiDnsPacket *avahi_recv_dns_packet_ipv4(
         goto fail;
     }
 
+    /* For corrupt packets FIONREAD returns zero size (See rhbz #607297) */
+    if (!ms)
+        goto fail;
+
     p = avahi_dns_packet_new(ms + AVAHI_DNS_PACKET_EXTRA_SIZE);
 
     io.iov_base = AVAHI_DNS_PACKET_DATA(p);
@@ -805,6 +809,10 @@ AvahiDnsPacket *avahi_recv_dns_packet_ipv6(
         goto fail;
     }
 
+    /* For corrupt packets FIONREAD returns zero size (See rhbz #607297) */
+    if (!ms)
+        goto fail;
+
     p = avahi_dns_packet_new(ms + AVAHI_DNS_PACKET_EXTRA_SIZE);
 
     io.iov_base = AVAHI_DNS_PACKET_DATA(p);