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/* This function serves as replacement for a missing fchownat function,
as well as a work around for the fchownat bug in glibc-2.4:
<http://lists.ubuntu.com/archives/ubuntu-users/2006-September/093218.html>
when the buggy fchownat-with-AT_SYMLINK_NOFOLLOW operates on a symlink, it
mistakenly affects the symlink referent, rather than the symlink itself.
Copyright (C) 2006-2007, 2009-2015 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include "openat.h"
#if !HAVE_FCHOWNAT
/* Replacement for Solaris' function by the same name.
Invoke chown or lchown on file, FILE, using OWNER and GROUP, in the
directory open on descriptor FD. If FLAG is AT_SYMLINK_NOFOLLOW, then
use lchown, otherwise, use chown. If possible, do it without changing
the working directory. Otherwise, resort to using save_cwd/fchdir,
then (chown|lchown)/restore_cwd. If either the save_cwd or the
restore_cwd fails, then give a diagnostic and exit nonzero. */
# define AT_FUNC_NAME fchownat
# define AT_FUNC_F1 lchown
# define AT_FUNC_F2 chown
# define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
# define AT_FUNC_POST_FILE_PARAM_DECLS , uid_t owner, gid_t group, int flag
# define AT_FUNC_POST_FILE_ARGS , owner, group
# include "at-func.c"
# undef AT_FUNC_NAME
# undef AT_FUNC_F1
# undef AT_FUNC_F2
# undef AT_FUNC_USE_F1_COND
# undef AT_FUNC_POST_FILE_PARAM_DECLS
# undef AT_FUNC_POST_FILE_ARGS
#else /* HAVE_FCHOWNAT */
# undef fchownat
# if FCHOWNAT_NOFOLLOW_BUG
/* Failure to handle AT_SYMLINK_NOFOLLOW requires the /proc/self/fd or
fchdir workaround to call lchown for lchownat, but there is no need
to penalize chownat. */
static int
local_lchownat (int fd, char const *file, uid_t owner, gid_t group);
# define AT_FUNC_NAME local_lchownat
# define AT_FUNC_F1 lchown
# define AT_FUNC_POST_FILE_PARAM_DECLS , uid_t owner, gid_t group
# define AT_FUNC_POST_FILE_ARGS , owner, group
# include "at-func.c"
# undef AT_FUNC_NAME
# undef AT_FUNC_F1
# undef AT_FUNC_POST_FILE_PARAM_DECLS
# undef AT_FUNC_POST_FILE_ARGS
# endif
/* Work around bugs with trailing slash, using the same workarounds as
chown and lchown. */
int
rpl_fchownat (int fd, char const *file, uid_t owner, gid_t group, int flag)
{
# if FCHOWNAT_NOFOLLOW_BUG
if (flag == AT_SYMLINK_NOFOLLOW)
return local_lchownat (fd, file, owner, group);
# endif
# if FCHOWNAT_EMPTY_FILENAME_BUG
if (file[0] == '\0')
{
errno = ENOENT;
return -1;
}
# endif
# if CHOWN_TRAILING_SLASH_BUG
{
size_t len = strlen (file);
struct stat st;
if (len && file[len - 1] == '/')
{
if (statat (fd, file, &st))
return -1;
if (flag == AT_SYMLINK_NOFOLLOW)
return fchownat (fd, file, owner, group, 0);
}
}
# endif
return fchownat (fd, file, owner, group, flag);
}
#endif /* HAVE_FCHOWNAT */
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