Fix underflow in socketAddr::address

With a regression test for issue #1403.

src/sys/unix/uds/socketaddr.rs

@@ -28,6 +28,10 @@ enum AddressKind<'a> {
 impl SocketAddr {
     fn address(&self) -> AddressKind<'_> {
         let offset = path_offset(&self.sockaddr);
+        // Don't underflow in `len` below.
+        if (self.socklen as usize) < offset {
+            return AddressKind::Unnamed;
+        }
         let len = self.socklen as usize - offset;
         let path = unsafe { &*(&self.sockaddr.sun_path as *const [libc::c_char] as *const [u8]) };
 

tests/regressions.rs

@@ -1,14 +1,15 @@
 #![cfg(all(feature = "os-poll", feature = "net"))]
 
-use mio::net::{TcpListener, TcpStream};
-use mio::{Events, Interest, Poll, Token, Waker};
 use std::io::{self, Read};
 use std::sync::Arc;
 use std::time::Duration;
 use std::{net, thread};
 
+use mio::net::{TcpListener, TcpStream};
+use mio::{Events, Interest, Poll, Token, Waker};
+
 mod util;
-use util::{any_local_address, init, init_with_poll};
+use util::{any_local_address, init, init_with_poll, temp_file};
 
 const ID1: Token = Token(1);
 const WAKE_TOKEN: Token = Token(10);
@@ -103,3 +104,22 @@ fn issue_1205() {
     assert_eq!(waker_event.token(), WAKE_TOKEN);
     handle.join().unwrap();
 }
+
+#[test]
+#[cfg(unix)]
+fn issue_1403() {
+    use mio::net::UnixDatagram;
+
+    init();
+
+    let path = temp_file("issue_1403");
+    let datagram1 = UnixDatagram::bind(&path).unwrap();
+    let datagram2 = UnixDatagram::unbound().unwrap();
+
+    let mut buf = [1u8; 1024];
+    let n = datagram2.send_to(&buf, &path).unwrap();
+
+    let (got, addr) = datagram1.recv_from(&mut buf).unwrap();
+    assert_eq!(got, n);
+    assert_eq!(addr.as_pathname(), None);
+}