Close all non-stdio FDs in virt-login-shell (CVE-2013-4400)

We don't want to inherit any FDs in the new namespace
except for the stdio FDs. Explicitly close them all,
just in case some do not have the close-on-exec flag
set.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

tools/virt-login-shell.c

@@ -313,6 +313,18 @@ main(int argc, char **argv)
     if (cpid == 0) {
         pid_t ccpid;
 
+        int openmax = sysconf(_SC_OPEN_MAX);
+        int fd;
+        if (openmax < 0) {
+            virReportSystemError(errno,  "%s",
+                                 _("sysconf(_SC_OPEN_MAX) failed"));
+            return EXIT_FAILURE;
+        }
+        for (fd = 3; fd < openmax; fd++) {
+            int tmpfd = fd;
+            VIR_MASS_CLOSE(tmpfd);
+        }
+
         /* Fork once because we don't want to affect
          * virt-login-shell's namespace itself
          */