avoid leaking netlink socket fd to external programs

The netlink socket is now used by udev event processes. We should take
care not to pass it to the programs they execute. This is the same way
the inotify fd was handled.

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>

udev/lib/libudev-monitor.c

@@ -92,6 +92,8 @@ struct udev_monitor *udev_monitor_new_from_socket(struct udev *udev, const char
 		free(udev_monitor);
 		return NULL;
 	}
+	util_set_fd_cloexec(udev_monitor->sock);
+
 	dbg(udev, "monitor %p created with '%s'\n", udev_monitor, socket_path);
 	return udev_monitor;
 }
@@ -125,6 +127,7 @@ struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char
 		free(udev_monitor);
 		return NULL;
 	}
+	util_set_fd_cloexec(udev_monitor->sock);
 
 	udev_monitor->snl.nl_family = AF_NETLINK;
 	udev_monitor->snl.nl_groups = group;

udev/lib/libudev-private.h

@@ -172,4 +172,5 @@ extern size_t util_strlcat(char *dst, const char *src, size_t size);
 extern int udev_util_replace_whitespace(const char *str, char *to, size_t len);
 extern int udev_util_replace_chars(char *str, const char *white);
 extern int udev_util_encode_string(const char *str, char *str_enc, size_t len);
+extern void util_set_fd_cloexec(int fd);
 #endif

udev/lib/libudev-util.c

@@ -448,3 +448,15 @@ int udev_util_encode_string(const char *str, char *str_enc, size_t len)
 err:
 	return -1;
 }
+
+void util_set_fd_cloexec(int fd)
+{
+	int flags;
+
+	flags = fcntl(fd, F_GETFD);
+	if (flags < 0)
+		flags = FD_CLOEXEC;
+	else
+		flags |= FD_CLOEXEC;
+	fcntl(fd, F_SETFD, flags);
+}

udev/udev-watch.c

@@ -41,16 +41,9 @@ int inotify_fd = -1;
 void udev_watch_init(struct udev *udev)
 {
 	inotify_fd = inotify_init();
-	if (inotify_fd >= 0) {
-		int flags;
-
-		flags = fcntl(inotify_fd, F_GETFD);
-		if (flags < 0)
-			flags = FD_CLOEXEC;
-		else
-			flags |= FD_CLOEXEC;
-		fcntl(inotify_fd, F_SETFD, flags);
-	} else if (errno == ENOSYS)
+	if (inotify_fd >= 0)
+		util_set_fd_cloexec(inotify_fd);
+	else if (errno == ENOSYS)
 		info(udev, "unable to use inotify, udevd will not monitor rule files changes\n");
 	else
 		err(udev, "inotify_init failed: %m\n");