gdbstub: Handle errors in gdb_accept()

In gdb_accept(), we both fail to check all errors (notably
that from socket_set_nodelay(), as Coverity notes in CID 1005666),
and fail to return an error status back to our caller. Correct
both of these things, so that errors in accept() result in our
stopping with a useful error message rather than ignoring it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

gdbstub.c

@@ -1814,7 +1814,7 @@ void gdb_signalled(CPUArchState *env, int sig)
     put_packet(s, buf);
 }
 
-static void gdb_accept(void)
+static bool gdb_accept(void)
 {
     GDBState *s;
     struct sockaddr_in sockaddr;
@@ -1826,7 +1826,7 @@ static void gdb_accept(void)
         fd = accept(gdbserver_fd, (struct sockaddr *)&sockaddr, &len);
         if (fd < 0 && errno != EINTR) {
             perror("accept");
-            return;
+            return false;
         } else if (fd >= 0) {
             qemu_set_cloexec(fd);
             break;
@@ -1834,7 +1834,10 @@ static void gdb_accept(void)
     }
 
     /* set short latency */
-    socket_set_nodelay(fd);
+    if (socket_set_nodelay(fd)) {
+        perror("setsockopt");
+        return false;
+    }
 
     s = g_malloc0(sizeof(GDBState));
     s->c_cpu = first_cpu;
@@ -1843,6 +1846,7 @@ static void gdb_accept(void)
     gdb_has_xml = false;
 
     gdbserver_state = s;
+    return true;
 }
 
 static int gdbserver_open(int port)
@@ -1883,7 +1887,11 @@ int gdbserver_start(int port)
     if (gdbserver_fd < 0)
         return -1;
     /* accept connections */
-    gdb_accept();
+    if (!gdb_accept()) {
+        close(gdbserver_fd);
+        gdbserver_fd = -1;
+        return -1;
+    }
     return 0;
 }