Use O_CLOEXEC when creating FDs

This is needed so that new processes (created with fork+exec) don't
inherit open files, which can be important for a number of reasons.

Since O_CLOEXEC is relatively new (POSIX.1-2008, before that Linux
specific), we #define it to 0 in io.h to prevent compilation errors on
older/crappy systems. At least this is the plan.

input.c creates a pipe. For that, add a mp_set_cloexec() function (which
is based on Weston's code in vo_wayland.c, but more correct). We could
use pipe2() instead, but that is Linux specific. Technically, we have a
race condition, but it won't matter.

2 files changed, 28 insertions, 1 deletions

diff --git a/osdep/io.c b/osdep/io.c
index 94bd90a676..4ad00d8df3 100644
--- a/osdep/io.c
+++ b/osdep/io.c
@@ -19,6 +19,23 @@
  */
 
 #include "config.h"
+#include "osdep/io.h"
+
+// Set the CLOEXEC flag on the given fd.
+// On error, false is returned (and errno set).
+bool mp_set_cloexec(int fd)
+{
+#if defined(FD_CLOEXEC) && defined(F_SETFD)
+    if (fd >= 0) {
+        int flags = fcntl(fd, F_GETFD);
+        if (flags == -1)
+            return false;
+        if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
+            return false;
+    }
+#endif
+    return true;
+}
 
 #ifdef _WIN32
 
@@ -27,7 +44,6 @@
 #include <stdio.h>
 #include <stddef.h>
 
-#include "osdep/io.h"
 #include "talloc.h"
 
 //copied and modified from libav
diff --git a/osdep/io.h b/osdep/io.h
index d855e852eb..aa20446210 100644
--- a/osdep/io.h
+++ b/osdep/io.h
@@ -20,7 +20,18 @@
 #ifndef MPLAYER_OSDEP_IO
 #define MPLAYER_OSDEP_IO
 
+#include <stdbool.h>
 #include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+// This is in POSIX.1-2008, but support outside of Linux is scarce.
+#ifndef O_CLOEXEC
+#define O_CLOEXEC 0
+#endif
+
+bool mp_set_cloexec(int fd);
 
 #ifdef _WIN32
 #include <wchar.h>