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(check_one_fd): For writable descriptors, use /dev/full. (__libc_check_standard_fds): Revert modes so that common operations on the descriptors fail.

This commit is contained in:
Ulrich Drepper 2005-11-09 19:26:07 +00:00
parent 7fe72b72ea
commit 1fdf81587d
1 changed files with 22 additions and 10 deletions
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32
sysdeps/generic/check_fds.c
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@ -1,4 +1,4 @@
/* Copyright (C) 2000, 2002, 2003 Free Software Foundation, Inc. /* Copyright (C) 2000, 2002, 2003, 2005 Free Software Foundation, Inc.
This file is part of the GNU C Library. This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or The GNU C Library is free software; you can redistribute it and/or
@ -44,12 +44,26 @@ check_one_fd (int fd, int mode)
if (__builtin_expect (__libc_fcntl (fd, F_GETFD), 0) == -1 if (__builtin_expect (__libc_fcntl (fd, F_GETFD), 0) == -1
&& errno == EBADF) && errno == EBADF)
{ {
struct stat64 st; 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 /* Something is wrong with this descriptor, it's probably not
opened. Open /dev/null so that the SUID program we are opened. Open /dev/null so that the SUID program we are
about to start does not accidently use this descriptor. */ about to start does not accidently use this descriptor. */
int nullfd = open_not_cancel (_PATH_DEVNULL, mode, 0); int nullfd = open_not_cancel (name, mode, 0);
/* We are very paranoid here. With all means we try to ensure /* We are very paranoid here. With all means we try to ensure
that we are actually opening the /dev/null device and nothing that we are actually opening the /dev/null device and nothing
else. else.
@ -57,13 +71,11 @@ check_one_fd (int fd, int mode)
Note that the following code assumes that STDIN_FILENO, Note that the following code assumes that STDIN_FILENO,
STDOUT_FILENO, STDERR_FILENO are the three lowest file STDOUT_FILENO, STDERR_FILENO are the three lowest file
decsriptor numbers, in this order. */ decsriptor numbers, in this order. */
struct stat64 st;
if (__builtin_expect (nullfd != fd, 0) if (__builtin_expect (nullfd != fd, 0)
|| __builtin_expect (__fxstat64 (_STAT_VER, fd, &st), 0) != 0 || __builtin_expect (__fxstat64 (_STAT_VER, fd, &st), 0) != 0
|| __builtin_expect (S_ISCHR (st.st_mode), 1) == 0 || __builtin_expect (S_ISCHR (st.st_mode), 1) == 0
#if defined DEV_NULL_MAJOR && defined DEV_NULL_MINOR || st.st_rdev != dev)
|| st.st_rdev != makedev (DEV_NULL_MAJOR, DEV_NULL_MINOR)
#endif
)
/* We cannot even give an error message here since it would /* We cannot even give an error message here since it would
run into the same problems. */ run into the same problems. */
while (1) while (1)
@ -84,7 +96,7 @@ __libc_check_standard_fds (void)
# define O_NOFOLLOW 0 # define O_NOFOLLOW 0
#endif #endif
/* Check all three standard file descriptors. */ /* Check all three standard file descriptors. */
check_one_fd (STDIN_FILENO, O_RDONLY | O_NOFOLLOW); check_one_fd (STDIN_FILENO, O_WRONLY | O_NOFOLLOW);
check_one_fd (STDOUT_FILENO, O_RDWR | O_NOFOLLOW); check_one_fd (STDOUT_FILENO, O_RDONLY | O_NOFOLLOW);
check_one_fd (STDERR_FILENO, O_RDWR | O_NOFOLLOW); check_one_fd (STDERR_FILENO, O_RDONLY | O_NOFOLLOW);
} }