diff options
Diffstat (limited to 'sysdeps/generic/check_fds.c')
-rw-r--r-- | sysdeps/generic/check_fds.c | 62 |
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); +} |