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authorUlrich Drepper <drepper@redhat.com>2004-12-22 20:10:10 +0000
committerUlrich Drepper <drepper@redhat.com>2004-12-22 20:10:10 +0000
commita334319f6530564d22e775935d9c91663623a1b4 (patch)
treeb5877475619e4c938e98757d518bb1e9cbead751 /sysdeps/generic/check_fds.c
parent0ecb606cb6cf65de1d9fc8a919bceb4be476c602 (diff)
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(CFLAGS-tst-align.c): Add -mpreferred-stack-boundary=4.
Diffstat (limited to 'sysdeps/generic/check_fds.c')
-rw-r--r--sysdeps/generic/check_fds.c90
1 files changed, 90 insertions, 0 deletions
diff --git a/sysdeps/generic/check_fds.c b/sysdeps/generic/check_fds.c
new file mode 100644
index 0000000000..5ae3feee3e
--- /dev/null
+++ b/sysdeps/generic/check_fds.c
@@ -0,0 +1,90 @@
+/* Copyright (C) 2000, 2002, 2003 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 Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; 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>
+#include <sys/stat.h>
+#include <sys/sysmacros.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
+
+#include <device-nrs.h>
+#include <not-cancel.h>
+
+
+/* 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)
+{
+ /* Note that fcntl() with this parameter is not a cancellation point. */
+ if (__builtin_expect (__libc_fcntl (fd, F_GETFD), 0) == -1
+ && errno == EBADF)
+ {
+ struct stat64 st;
+
+ /* 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 = open_not_cancel (_PATH_DEVNULL, mode, 0);
+ /* We are very paranoid here. With all means we try to ensure
+ that we are actually opening the /dev/null device and nothing
+ else.
+
+ Note that the following code assumes that STDIN_FILENO,
+ STDOUT_FILENO, STDERR_FILENO are the three lowest file
+ decsriptor numbers, in this order. */
+ if (__builtin_expect (nullfd != fd, 0)
+ || __builtin_expect (__fxstat64 (_STAT_VER, fd, &st), 0) != 0
+ || __builtin_expect (S_ISCHR (st.st_mode), 1) == 0
+#if defined DEV_NULL_MAJOR && defined DEV_NULL_MINOR
+ || st.st_rdev != makedev (DEV_NULL_MAJOR, DEV_NULL_MINOR)
+#endif
+ )
+ /* 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)
+{
+ /* This is really paranoid but some people actually are. If /dev/null
+ should happen to be a symlink to somewhere else and not the device
+ commonly known as "/dev/null" we bail out. We can detect this with
+ the O_NOFOLLOW flag for open() but only on some system. */
+#ifndef O_NOFOLLOW
+# define O_NOFOLLOW 0
+#endif
+ /* Check all three standard file descriptors. */
+ check_one_fd (STDIN_FILENO, O_RDONLY | O_NOFOLLOW);
+ check_one_fd (STDOUT_FILENO, O_RDWR | O_NOFOLLOW);
+ check_one_fd (STDERR_FILENO, O_RDWR | O_NOFOLLOW);
+}