set the close-on-exec flag on all file descriptors

Added the "fd_util" library, which attempts to use the new thread-safe
Linux system calls pipe2(), accept4() and the options O_CLOEXEC,
SOCK_CLOEXEC.  Without these, it falls back to FD_CLOEXEC, which is
not thread safe.

This is particularly important for the "pipe" output plugin (and
others, such as JACK/PulseAudio), because we were heavily leaking file
descriptors to child processes.

Makefile.am

@@ -72,6 +72,7 @@ mpd_headers = \
 	src/encoder_list.h \
 	src/encoder_api.h \
 	src/exclude.h \
+	src/fd_util.h \
 	src/fifo_buffer.h \
 	src/update.h \
 	src/update_internal.h \
@@ -220,6 +221,7 @@ src_mpd_SOURCES = \
 	src/database.c \
 	src/dirvec.c \
 	src/exclude.c \
+	src/fd_util.c \
 	src/fifo_buffer.c \
 	src/filter_plugin.c \
 	src/filter_registry.c \
@@ -738,6 +740,7 @@ test_run_input_LDADD = $(MPD_LIBS) \
 test_run_input_SOURCES = test/run_input.c \
 	src/conf.c src/tokenizer.c src/utils.c \
 	src/tag.c src/tag_pool.c src/tag_save.c \
+	src/fd_util.c \
 	$(ARCHIVE_SRC) \
 	$(INPUT_SRC)
 
@@ -753,6 +756,7 @@ test_dump_playlist_SOURCES = test/dump_playlist.c \
 	src/uri.c \
 	src/song.c src/tag.c src/tag_pool.c src/tag_save.c \
 	src/text_input_stream.c src/fifo_buffer.c \
+	src/fd_util.c \
 	$(ARCHIVE_SRC) \
 	$(INPUT_SRC) \
 	$(PLAYLIST_SRC)
@@ -771,6 +775,7 @@ test_run_decoder_SOURCES = test/run_decoder.c \
 	src/tag.c src/tag_pool.c \
 	src/replay_gain.c \
 	src/uri.c \
+	src/fd_util.c \
 	$(ARCHIVE_SRC) \
 	$(INPUT_SRC) \
 	$(TAG_SRC) \
@@ -790,6 +795,7 @@ test_read_tags_SOURCES = test/read_tags.c \
 	src/tag.c src/tag_pool.c \
 	src/replay_gain.c \
 	src/uri.c \
+	src/fd_util.c \
 	$(ARCHIVE_SRC) \
 	$(INPUT_SRC) \
 	$(TAG_SRC) \
@@ -857,6 +863,7 @@ test_run_output_SOURCES = test/run_output.c \
 	src/filter/convert_filter_plugin.c \
 	src/filter/volume_filter_plugin.c \
 	src/pcm_volume.c \
+	src/fd_util.c \
 	$(OUTPUT_SRC)
 
 test_read_mixer_CPPFLAGS = $(AM_CPPFLAGS) \
@@ -869,6 +876,7 @@ test_read_mixer_SOURCES = test/read_mixer.c \
 	src/mixer_control.c src/mixer_api.c \
 	src/filter_plugin.c \
 	src/filter/volume_filter_plugin.c \
+	src/fd_util.c \
 	$(MIXER_SRC)
 
 endif

NEWS

@@ -62,6 +62,7 @@ ver 0.16 (20??/??/??)
 * state_file: save only if something has changed
 * database: eliminated maximum line length
 * log: redirect stdout/stderr to /dev/null if syslog is used
+* set the close-on-exec flag on all file descriptors
 * obey $(sysconfdir) for default mpd.conf location
 * build with large file support by default
 * require GLib 2.16

configure.ac

@@ -115,12 +115,14 @@ fi
 AC_CHECK_LIB(socket,socket,MPD_LIBS="$MPD_LIBS -lsocket",)
 AC_CHECK_LIB(nsl,gethostbyname,MPD_LIBS="$MPD_LIBS -lnsl",)
 
+AC_CHECK_FUNCS(pipe2 accept4)
+
 AC_CHECK_LIB(m,exp,MPD_LIBS="$MPD_LIBS -lm",)
 
 AC_CHECK_HEADERS(locale.h)
 AC_CHECK_HEADERS(valgrind/memcheck.h)
 
-AC_CHECK_FUNCS(inotify_init)
+AC_CHECK_FUNCS(inotify_init inotify_init1)
 AC_ARG_ENABLE(inotify,
 	AS_HELP_STRING([--disable-inotify],
 		[disable support Inotify automatic database update (default: enabled) ]),,

src/event_pipe.c

@@ -19,6 +19,7 @@
 
 #include "event_pipe.h"
 #include "utils.h"
+#include "fd_util.h"
 
 #include <stdbool.h>
 #include <assert.h>
@@ -84,11 +85,7 @@ void event_pipe_init(void)
 	GIOChannel *channel;
 	int ret;
 
-#ifdef WIN32
+	ret = pipe_cloexec(event_pipe);
-	ret = _pipe(event_pipe, 512, _O_BINARY);
-#else
-	ret = pipe(event_pipe);
-#endif
 	if (ret < 0)
 		g_error("Couldn't open pipe: %s", strerror(errno));
 #ifndef WIN32

src/fd_util.c

@@ -0,0 +1,171 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "fd_util.h"
+#include "config.h"
+
+#if !defined(_GNU_SOURCE) && (defined(HAVE_PIPE2) || defined(HAVE_ACCEPT4))
+#define _GNU_SOURCE
+#endif
+
+#include <assert.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#ifdef WIN32
+#include <winsock2.h>
+#else
+#include <sys/socket.h>
+#endif
+
+#ifndef WIN32
+
+static int
+fd_mask_flags(int fd, int and_mask, int xor_mask)
+{
+	int ret;
+
+	assert(fd >= 0);
+
+	ret = fcntl(fd, F_GETFD, 0);
+	if (ret < 0)
+		return ret;
+
+	return fcntl(fd, F_SETFD, (ret & and_mask) ^ xor_mask);
+}
+
+#endif /* !WIN32 */
+
+int
+fd_set_cloexec(int fd, bool enable)
+{
+#ifndef WIN32
+	return fd_mask_flags(fd, ~FD_CLOEXEC, enable ? FD_CLOEXEC : 0);
+#else
+	(void)fd;
+	(void)enable;
+#endif
+}
+
+int
+open_cloexec(const char *path_fs, int flags)
+{
+	int fd;
+
+#ifdef O_CLOEXEC
+	flags |= O_CLOEXEC;
+#endif
+
+#ifdef O_NOCTTY
+	flags |= O_NOCTTY;
+#endif
+
+	fd = open(path_fs, flags, 0666);
+	fd_set_cloexec(fd, true);
+
+	return fd;
+}
+
+int
+creat_cloexec(const char *path_fs, int mode)
+{
+	int flags = O_CREAT|O_WRONLY|O_TRUNC;
+	int fd;
+
+#ifdef O_CLOEXEC
+	flags |= O_CLOEXEC;
+#endif
+
+#ifdef O_NOCTTY
+	flags |= O_NOCTTY;
+#endif
+
+	fd = open(path_fs, flags, mode);
+	fd_set_cloexec(fd, true);
+
+	return fd;
+}
+
+int
+pipe_cloexec(int fd[2])
+{
+#ifdef WIN32
+	return _pipe(event_pipe, 512, _O_BINARY);
+#else
+	int ret;
+
+#ifdef HAVE_PIPE2
+	ret = pipe2(fd, O_CLOEXEC);
+	if (ret >= 0 || errno != ENOSYS)
+		return ret;
+#endif
+
+	ret = pipe(fd);
+	if (ret >= 0) {
+		fd_set_cloexec(fd[0], true);
+		fd_set_cloexec(fd[1], true);
+	}
+
+	return ret;
+#endif
+}
+
+int
+socket_cloexec(int domain, int type, int protocol)
+{
+	int fd;
+
+#ifdef SOCK_CLOEXEC
+	fd = socket(domain, type | SOCK_CLOEXEC, protocol);
+	if (fd >= 0 || errno != EINVAL)
+		return fd;
+#endif
+
+	fd = socket(domain, type, protocol);
+	if (fd >= 0)
+		fd_set_cloexec(fd, true);
+
+	return fd;
+}
+
+int
+accept_cloexec(int fd, struct sockaddr *address, size_t *address_length_r)
+{
+	int ret;
+	socklen_t address_length = *address_length_r;
+
+#ifdef HAVE_ACCEPT4
+	ret = accept4(fd, address, &address_length, SOCK_CLOEXEC);
+	if (ret >= 0 || errno != ENOSYS) {
+		if (ret >= 0)
+			*address_length_r = address_length;
+
+		return ret;
+	}
+#endif
+
+	ret = accept(fd, address, &address_length);
+	if (ret >= 0) {
+		fd_set_cloexec(ret, true);
+		*address_length_r = address_length;
+	}
+
+	return ret;
+}

src/fd_util.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*
+ * This library provides easy helper functions for working with file
+ * descriptors.  It has wrappers for taking advantage of Linux 2.6
+ * specific features like O_CLOEXEC.
+ *
+ */
+
+#ifndef FD_UTIL_H
+#define FD_UTIL_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+struct sockaddr;
+
+int
+fd_set_cloexec(int fd, bool enable);
+
+int
+open_cloexec(const char *path_fs, int flags);
+
+int
+creat_cloexec(const char *path_fs, int mode);
+
+int
+pipe_cloexec(int fd[2]);
+
+int
+socket_cloexec(int domain, int type, int protocol);
+
+int
+accept_cloexec(int fd, struct sockaddr *address, size_t *address_length_r);
+
+#endif

src/input/file_input_plugin.c

@@ -20,6 +20,7 @@
 #include "config.h" /* must be first for large file support */
 #include "input/file_input_plugin.h"
 #include "input_plugin.h"
+#include "fd_util.h"
 
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -50,7 +51,7 @@ input_file_open(struct input_stream *is, const char *filename)
 		*slash = '\0';
 	}
 
-	fd = open(pathname, O_RDONLY);
+	fd = open_cloexec(pathname, O_RDONLY);
 	if (fd < 0) {
 		is->error = errno;
 		g_debug("Failed to open \"%s\": %s",

src/listen.c

@@ -22,6 +22,7 @@
 #include "client.h"
 #include "conf.h"
 #include "utils.h"
+#include "fd_util.h"
 #include "config.h"
 
 #include <sys/types.h>
@@ -426,9 +427,9 @@ listen_in_event(G_GNUC_UNUSED GIOChannel *source,
 {
 	int listen_fd = GPOINTER_TO_INT(data), fd;
 	struct sockaddr_storage sa;
-	socklen_t sa_length = sizeof(sa);
+	size_t sa_length = sizeof(sa);
 
-	fd = accept(listen_fd, (struct sockaddr*)&sa, &sa_length);
+	fd = accept_cloexec(listen_fd, (struct sockaddr*)&sa, &sa_length);
 	if (fd >= 0) {
 		set_nonblocking(fd);
 

src/log.c

@@ -20,6 +20,7 @@
 #include "log.h"
 #include "conf.h"
 #include "utils.h"
+#include "fd_util.h"
 #include "config.h"
 
 #include <assert.h>
@@ -128,7 +129,7 @@ open_log_file(void)
 {
 	assert(out_filename != NULL);
 
-	return open(out_filename, O_CREAT | O_WRONLY | O_APPEND, 0666);
+	return open_cloexec(out_filename, O_CREAT | O_WRONLY | O_APPEND);
 }
 
 static void

src/mixer/oss_mixer_plugin.c

@@ -19,6 +19,7 @@
 
 #include "mixer_api.h"
 #include "output_api.h"
+#include "fd_util.h"
 
 #include <glib.h>
 
@@ -122,7 +123,7 @@ oss_mixer_open(struct mixer *data, GError **error_r)
 {
 	struct oss_mixer *om = (struct oss_mixer *) data;
 
-	om->device_fd = open(om->device, O_RDONLY);
+	om->device_fd = open_cloexec(om->device, O_RDONLY);
 	if (om->device_fd < 0) {
 		g_set_error(error_r, oss_mixer_quark(), errno,
 			    "failed to open %s: %s",

src/output/fifo_output_plugin.c

@@ -20,6 +20,7 @@
 #include "output_api.h"
 #include "utils.h"
 #include "timer.h"
+#include "fd_util.h"
 
 #include <glib.h>
 
@@ -152,7 +153,7 @@ fifo_open(struct fifo_data *fd, GError **error)
 	if (!fifo_check(fd, error))
 		return false;
 
-	fd->input = open(fd->path, O_RDONLY|O_NONBLOCK);
+	fd->input = open_cloexec(fd->path, O_RDONLY|O_NONBLOCK);
 	if (fd->input < 0) {
 		g_set_error(error, fifo_output_quark(), errno,
 			    "Could not open FIFO \"%s\" for reading: %s",
@@ -161,7 +162,7 @@ fifo_open(struct fifo_data *fd, GError **error)
 		return false;
 	}
 
-	fd->output = open(fd->path, O_WRONLY|O_NONBLOCK);
+	fd->output = open_cloexec(fd->path, O_WRONLY|O_NONBLOCK);
 	if (fd->output < 0) {
 		g_set_error(error, fifo_output_quark(), errno,
 			    "Could not open FIFO \"%s\" for writing: %s",

src/output/httpd_output_plugin.c

@@ -25,6 +25,7 @@
 #include "socket_util.h"
 #include "page.h"
 #include "icy_server.h"
+#include "fd_util.h"
 
 #include <assert.h>
 
@@ -187,14 +188,14 @@ httpd_listen_in_event(G_GNUC_UNUSED GIOChannel *source,
 	struct httpd_output *httpd = data;
 	int fd;
 	struct sockaddr_storage sa;
-	socklen_t sa_length = sizeof(sa);
+	size_t sa_length = sizeof(sa);
 
 	g_mutex_lock(httpd->mutex);
 
 	/* the listener socket has become readable - a client has
 	   connected */
 
-	fd = accept(httpd->fd, (struct sockaddr*)&sa, &sa_length);
+	fd = accept_cloexec(httpd->fd, (struct sockaddr*)&sa, &sa_length);
 	if (fd >= 0) {
 		/* can we allow additional client */
 		if (httpd->open &&

src/output/mvp_plugin.c

@@ -22,7 +22,8 @@
  * http://mvpmc.sourceforge.net/
  */
 
-#include "../output_api.h"
+#include "output_api.h"
+#include "fd_util.h"
 
 #include <glib.h>
 
@@ -115,7 +116,7 @@ mvp_output_test_default_device(void)
 {
 	int fd;
 
-	fd = open("/dev/adec_pcm", O_WRONLY);
+	fd = open_cloexec("/dev/adec_pcm", O_WRONLY);
 
 	if (fd >= 0) {
 		close(fd);
@@ -230,7 +231,8 @@ mvp_output_open(void *data, struct audio_format *audio_format, GError **error)
 	int mix[5] = { 0, 2, 7, 1, 0 };
 	bool success;
 
-	if ((md->fd = open("/dev/adec_pcm", O_RDWR | O_NONBLOCK)) < 0) {
+	md->fd = open_cloexec("/dev/adec_pcm", O_RDWR | O_NONBLOCK);
+	if (md->fd < 0) {
 		g_set_error(error, mvp_output_quark(), errno,
 			    "Error opening /dev/adec_pcm: %s",
 			    strerror(errno));

src/output/oss_plugin.c

@@ -17,8 +17,9 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#include "../output_api.h"
+#include "output_api.h"
 #include "mixer_list.h"
+#include "fd_util.h"
 
 #include <glib.h>
 
@@ -343,7 +344,9 @@ oss_output_test_default_device(void)
 	int fd, i;
 
 	for (i = G_N_ELEMENTS(default_devices); --i >= 0; ) {
-		if ((fd = open(default_devices[i], O_WRONLY)) >= 0) {
+		fd = open_cloexec(default_devices[i], O_WRONLY);
+
+		if (fd >= 0) {
 			close(fd);
 			return true;
 		}
@@ -516,7 +519,8 @@ oss_open(struct oss_data *od, GError **error)
 {
 	bool success;
 
-	if ((od->fd = open(od->device, O_WRONLY)) < 0) {
+	od->fd = open_cloexec(od->device, O_WRONLY);
+	if (od->fd < 0) {
 		g_set_error(error, oss_output_quark(), errno,
 			    "Error opening OSS device \"%s\": %s",
 			    od->device, strerror(errno));

src/output/recorder_output_plugin.c

@@ -20,6 +20,7 @@
 #include "output_api.h"
 #include "encoder_plugin.h"
 #include "encoder_list.h"
+#include "fd_util.h"
 
 #include <assert.h>
 #include <sys/types.h>
@@ -156,7 +157,7 @@ recorder_output_open(void *data, struct audio_format *audio_format,
 
 	/* create the output file */
 
-	recorder->fd = creat(recorder->path, 0666);
+	recorder->fd = creat_cloexec(recorder->path, 0666);
 	if (recorder->fd < 0) {
 		g_set_error(error_r, recorder_output_quark(), 0,
 			    "Failed to create '%s': %s",

src/output/solaris_output_plugin.c

@@ -18,6 +18,7 @@
  */
 
 #include "output_api.h"
+#include "fd_util.h"
 
 #include <glib.h>
 
@@ -91,7 +92,7 @@ solaris_output_open(void *data, struct audio_format *audio_format,
 
 	/* open the device in non-blocking mode */
 
-	so->fd = open(so->device, O_WRONLY|O_NONBLOCK);
+	so->fd = open_cloexec(so->device, O_WRONLY|O_NONBLOCK);
 	if (so->fd < 0) {
 		g_set_error(error, solaris_output_quark(), errno,
 			    "Failed to open %s: %s",

src/socket_util.c

@@ -18,6 +18,7 @@
  */
 
 #include "socket_util.h"
+#include "fd_util.h"
 #include "config.h"
 
 #include <errno.h>
@@ -102,7 +103,7 @@ socket_bind_listen(int domain, int type, int protocol,
 	int passcred = 1;
 #endif
 
-	fd = socket(domain, type, protocol);
+	fd = socket_cloexec(domain, type, protocol);
 	if (fd < 0) {
 		g_set_error(error, listen_quark(), errno,
 			    "Failed to create socket: %s", g_strerror(errno));