unix: report errors for unpollable fds

Libuv would abort() when trying to watch a file descriptor that is
not compatible with epoll-style polling; file descriptors referring
to on-disk files fall into this category.

File descriptors that libuv creates itself are not an issue but
external ones that come in through the uv_poll_init() API are.

Make uv_poll_init() check whether the file descriptor is accepted by
the underlying system call and return an error when it's not.

Fixes: https://github.com/libuv/libuv/issues/658
PR-URL: https://github.com/libuv/libuv/pull/659
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

src/unix/aix.c

@@ -91,6 +91,24 @@ void uv__platform_loop_delete(uv_loop_t* loop) {
 }
 
 
+int uv__io_check_fd(uv_loop_t* loop, int fd) {
+  struct poll_ctl pc;
+
+  pc.events = POLLIN;
+  pc.cmd = PS_MOD;  /* Equivalent to PS_ADD if the fd is not in the pollset. */
+  pc.fd = fd;
+
+  if (pollset_ctl(loop->backend_fd, &pc, 1))
+    return -errno;
+
+  pc.cmd = PS_DELETE;
+  if (pollset_ctl(loop->backend_fd, &pc, 1))
+    abort();
+
+  return 0;
+}
+
+
 void uv__io_poll(uv_loop_t* loop, int timeout) {
   struct pollfd events[1024];
   struct pollfd pqry;

src/unix/internal.h

@@ -180,6 +180,7 @@ void uv__io_stop(uv_loop_t* loop, uv__io_t* w, unsigned int events);
 void uv__io_close(uv_loop_t* loop, uv__io_t* w);
 void uv__io_feed(uv_loop_t* loop, uv__io_t* w);
 int uv__io_active(const uv__io_t* w, unsigned int events);
+int uv__io_check_fd(uv_loop_t* loop, int fd);
 void uv__io_poll(uv_loop_t* loop, int timeout); /* in milliseconds or -1 */
 
 /* async */

src/unix/kqueue.c

@@ -48,6 +48,24 @@ int uv__kqueue_init(uv_loop_t* loop) {
 }
 
 
+int uv__io_check_fd(uv_loop_t* loop, int fd) {
+  struct kevent ev;
+  int rc;
+
+  rc = 0;
+  EV_SET(&ev, fd, EVFILT_READ, EV_ADD, 0, 0, 0);
+  if (kevent(loop->backend_fd, &ev, 1, NULL, 0, NULL))
+    rc = -errno;
+
+  EV_SET(&ev, fd, EVFILT_READ, EV_DELETE, 0, 0, 0);
+  if (rc == 0)
+    if (kevent(loop->backend_fd, &ev, 1, NULL, 0, NULL))
+      abort();
+
+  return rc;
+}
+
+
 void uv__io_poll(uv_loop_t* loop, int timeout) {
   struct kevent events[1024];
   struct kevent* ev;

src/unix/linux-core.c

@@ -140,6 +140,26 @@ void uv__platform_invalidate_fd(uv_loop_t* loop, int fd) {
 }
 
 
+int uv__io_check_fd(uv_loop_t* loop, int fd) {
+  struct uv__epoll_event e;
+  int rc;
+
+  e.events = UV__EPOLLIN;
+  e.data = -1;
+
+  rc = 0;
+  if (uv__epoll_ctl(loop->backend_fd, UV__EPOLL_CTL_ADD, fd, &e))
+    if (errno != EEXIST)
+      rc = -errno;
+
+  if (rc == 0)
+    if (uv__epoll_ctl(loop->backend_fd, UV__EPOLL_CTL_DEL, fd, &e))
+      abort();
+
+  return rc;
+}
+
+
 void uv__io_poll(uv_loop_t* loop, int timeout) {
   /* A bug in kernels < 2.6.37 makes timeouts larger than ~30 minutes
    * effectively infinite on 32 bits architectures.  To avoid blocking

src/unix/poll.c

@@ -53,6 +53,10 @@ static void uv__poll_io(uv_loop_t* loop, uv__io_t* w, unsigned int events) {
 int uv_poll_init(uv_loop_t* loop, uv_poll_t* handle, int fd) {
   int err;
 
+  err = uv__io_check_fd(loop, fd);
+  if (err)
+    return err;
+
   err = uv__nonblock(fd, 1);
   if (err)
     return err;

src/unix/sunos.c

@@ -116,6 +116,17 @@ void uv__platform_invalidate_fd(uv_loop_t* loop, int fd) {
 }
 
 
+int uv__io_check_fd(uv_loop_t* loop, int fd) {
+  if (port_associate(loop->backend_fd, PORT_SOURCE_FD, fd, POLLIN, 0))
+    return -errno;
+
+  if (port_dissociate(loop->backend_fd, PORT_SOURCE_FD, fd))
+    abort();
+
+  return 0;
+}
+
+
 void uv__io_poll(uv_loop_t* loop, int timeout) {
   struct port_event events[1024];
   struct port_event* pe;

test/test-list.h

@@ -305,6 +305,7 @@ TEST_DECLARE   (dlerror)
 TEST_DECLARE   (poll_duplex)
 TEST_DECLARE   (poll_unidirectional)
 TEST_DECLARE   (poll_close)
+TEST_DECLARE   (poll_bad_fdtype)
 
 TEST_DECLARE   (ip4_addr)
 TEST_DECLARE   (ip6_addr_link_local)
@@ -608,6 +609,7 @@ TASK_LIST_START
   TEST_ENTRY  (poll_duplex)
   TEST_ENTRY  (poll_unidirectional)
   TEST_ENTRY  (poll_close)
+  TEST_ENTRY  (poll_bad_fdtype)
 
   TEST_ENTRY  (socket_buffer_size)
 

test/test-poll.c

@@ -21,7 +21,9 @@
 
 #include <errno.h>
 
-#ifndef _WIN32
+#ifdef _WIN32
+# include <fcntl.h>
+#else
 # include <sys/socket.h>
 # include <unistd.h>
 #endif
@@ -558,3 +560,28 @@ TEST_IMPL(poll_unidirectional) {
   start_poll_test();
   return 0;
 }
+
+
+/* Windows won't let you open a directory so we open a file instead.
+ * OS X lets you poll a file so open the $PWD instead.  Both fail
+ * on Linux so it doesn't matter which one we pick.  Both succeed
+ * on FreeBSD and Solaris so skip the test on those platforms.
+ */
+TEST_IMPL(poll_bad_fdtype) {
+#if !defined(__DragonFly__) && !defined(__FreeBSD__) && !defined(__sun)
+  uv_poll_t poll_handle;
+  int fd;
+
+#if defined(_WIN32)
+  fd = open("test/fixtures/empty_file", O_RDONLY);
+#else
+  fd = open(".", O_RDONLY);
+#endif
+  ASSERT(fd != -1);
+  ASSERT(0 != uv_poll_init(uv_default_loop(), &poll_handle, fd));
+  ASSERT(0 == close(fd));
+#endif
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}