1 files changed, 62 insertions, 0 deletions
diff --git a/sysdeps/generic/check_fds.c b/sysdeps/generic/check_fds.c
new file mode 100644
index 0000000..4eea168
--- /dev/null
+++ b/sysdeps/generic/check_fds.c
@@ -0,0 +1,62 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <paths.h>
+#include <unistd.h>
+
+/* Try to get a machine dependent instruction which will make the
+   program crash.  This is used in case everything else fails.  */
+#include <abort-instr.h>
+#ifndef ABORT_INSTRUCTION
+/* No such instruction is available.  */
+# define ABORT_INSTRUCTION
+#endif
+
+
+/* Should other OSes (e.g., Hurd) have different versions which can
+   be written in a better way?  */
+static void
+check_one_fd (int fd, int mode)
+{
+  if (__builtin_expect (__libc_fcntl (fd, F_GETFD), 0) == -1
+      && errno == EBADF)
+    {
+      /* Something is wrong with this descriptor, it's probably not
+	 opened.  Open /dev/null so that the SUID program we are
+	 about to start does not accidently use this descriptor.  */
+      int nullfd = __libc_open (_PATH_DEVNULL, mode);
+      if (__builtin_expect (nullfd, 0) == -1)
+	/* We cannot even give an error message here since it would
+	   run into the same problems.  */
+	while (1)
+	  /* Try for ever and ever.  */
+	  ABORT_INSTRUCTION;
+    }
+}
+
+
+void
+__libc_check_standard_fds (void)
+{
+/* Check all three standard file descriptors.  */
+  check_one_fd (STDIN_FILENO, O_RDONLY);
+  check_one_fd (STDOUT_FILENO, O_RDWR);
+  check_one_fd (STDERR_FILENO, O_RDWR);
+}