mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-14 09:01:07 +00:00
103 lines
3.4 KiB
C
103 lines
3.4 KiB
C
/* Copyright (C) 2000, 2002, 2003, 2005 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)
|
|
{
|
|
const char *name;
|
|
dev_t dev;
|
|
|
|
/* For writable descriptors we use /dev/full. */
|
|
if ((mode & O_ACCMODE) == O_WRONLY)
|
|
{
|
|
name = _PATH_DEV "full";
|
|
dev = makedev (DEV_FULL_MAJOR, DEV_FULL_MINOR);
|
|
}
|
|
else
|
|
{
|
|
name = _PATH_DEVNULL;
|
|
dev = makedev (DEV_NULL_MAJOR, DEV_NULL_MINOR);
|
|
}
|
|
|
|
/* 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 (name, 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. */
|
|
struct stat64 st;
|
|
if (__builtin_expect (nullfd != fd, 0)
|
|
|| __builtin_expect (__fxstat64 (_STAT_VER, fd, &st), 0) != 0
|
|
|| __builtin_expect (S_ISCHR (st.st_mode), 1) == 0
|
|
|| st.st_rdev != dev)
|
|
/* 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_WRONLY | O_NOFOLLOW);
|
|
check_one_fd (STDOUT_FILENO, O_RDONLY | O_NOFOLLOW);
|
|
check_one_fd (STDERR_FILENO, O_RDONLY | O_NOFOLLOW);
|
|
}
|