unix: reject non-tty fds in uv_tty_init()

Reject file descriptors that correspond to regular files or char/block
devices.  Such file descriptors are incompatible with epoll and trigger
a run-time assert.

Fixes: https://github.com/libuv/libuv/issues/255
PR-URL: https://github.com/libuv/libuv/pull/259
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

docs/src/tty.rst

@@ -66,6 +66,10 @@ API
         If opening ``/dev/tty`` fails, libuv falls back to blocking writes for
         non-readable TTY streams.
 
+    .. versionchanged:: 1.5.0: trying to initialize a TTY stream with a file
+                        descriptor that refers to a file returns `UV_EINVAL`
+                        on UNIX.
+
 .. c:function:: int uv_tty_set_mode(uv_tty_t*, uv_tty_mode_t mode)
 
     .. versionchanged:: 1.2.0: the mode is specified as a

src/unix/tty.c

@@ -35,10 +35,19 @@ static uv_spinlock_t termios_spinlock = UV_SPINLOCK_INITIALIZER;
 
 
 int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
+  uv_handle_type type;
   int flags;
   int newfd;
   int r;
 
+  /* File descriptors that refer to files cannot be monitored with epoll.
+   * That restriction also applies to character devices like /dev/random
+   * (but obviously not /dev/tty.)
+   */
+  type = uv_guess_handle(fd);
+  if (type == UV_FILE || type == UV_UNKNOWN_HANDLE)
+    return -EINVAL;
+
   flags = 0;
   newfd = -1;
 
@@ -54,7 +63,7 @@ int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
    * different struct file, hence changing its properties doesn't affect
    * other processes.
    */
-  if (isatty(fd)) {
+  if (type == UV_TTY) {
     r = uv__open_cloexec("/dev/tty", O_RDWR);
 
     if (r < 0) {

test/test-list.h

@@ -43,6 +43,7 @@ TEST_DECLARE   (semaphore_1)
 TEST_DECLARE   (semaphore_2)
 TEST_DECLARE   (semaphore_3)
 TEST_DECLARE   (tty)
+TEST_DECLARE   (tty_file)
 TEST_DECLARE   (stdio_over_pipes)
 TEST_DECLARE   (ip6_pton)
 TEST_DECLARE   (ipc_listen_before_write)
@@ -343,6 +344,7 @@ TASK_LIST_START
 #endif
   TEST_ENTRY  (pipe_set_non_blocking)
   TEST_ENTRY  (tty)
+  TEST_ENTRY  (tty_file)
   TEST_ENTRY  (stdio_over_pipes)
   TEST_ENTRY  (ip6_pton)
   TEST_ENTRY  (ipc_listen_before_write)

test/test-tty.c

@@ -135,3 +135,45 @@ TEST_IMPL(tty) {
   MAKE_VALGRIND_HAPPY();
   return 0;
 }
+
+
+TEST_IMPL(tty_file) {
+#ifndef _WIN32
+  uv_loop_t loop;
+  uv_tty_t tty;
+  int fd;
+
+  ASSERT(0 == uv_loop_init(&loop));
+
+  fd = open("test/fixtures/empty_file", O_RDONLY);
+  if (fd != -1) {
+    ASSERT(UV_EINVAL == uv_tty_init(&loop, &tty, fd, 1));
+    ASSERT(0 == close(fd));
+  }
+
+  fd = open("/dev/random", O_RDONLY);
+  if (fd != -1) {
+    ASSERT(UV_EINVAL == uv_tty_init(&loop, &tty, fd, 1));
+    ASSERT(0 == close(fd));
+  }
+
+  fd = open("/dev/zero", O_RDONLY);
+  if (fd != -1) {
+    ASSERT(UV_EINVAL == uv_tty_init(&loop, &tty, fd, 1));
+    ASSERT(0 == close(fd));
+  }
+
+  fd = open("/dev/tty", O_RDONLY);
+  if (fd != -1) {
+    ASSERT(0 == uv_tty_init(&loop, &tty, fd, 1));
+    ASSERT(0 == close(fd));
+  }
+
+  uv_close((uv_handle_t*) &tty, NULL);
+  ASSERT(0 == uv_run(&loop, UV_RUN_DEFAULT));
+  ASSERT(0 == uv_loop_close(&loop));
+
+  MAKE_VALGRIND_HAPPY();
+#endif
+  return 0;
+}