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/* Copyright (C) 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 <stdio.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sysdep.h>
#include <stdlib.h>
#include <kernel-features.h>
/*
In Linux 2.1.x the chown functions have been changed. A new function lchown
was introduced. The new chown now follows symlinks - the old chown and the
new lchown do not follow symlinks.
This file emulates chown() under the old kernels.
*/
int
fchownat (int fd, const char *file, uid_t owner, gid_t group, int flag)
{
int result;
#ifdef __NR_fchownat
# ifndef __ASSUME_ATFCTS
if (__have_atfcts >= 0)
# endif
{
result = INLINE_SYSCALL (fchownat, 5, fd, file, owner, group, flag);
# ifndef __ASSUME_ATFCTS
if (result == -1 && errno == ENOSYS)
__have_atfcts = -1;
else
# endif
return result;
}
#endif
#ifndef __ASSUME_ATFCTS
if (flag & ~AT_SYMLINK_NOFOLLOW)
{
__set_errno (EINVAL);
return -1;
}
char *buf = NULL;
if (fd != AT_FDCWD && file[0] != '/')
{
size_t filelen = strlen (file);
static const char procfd[] = "/proc/self/fd/%d/%s";
/* Buffer for the path name we are going to use. It consists of
- the string /proc/self/fd/
- the file descriptor number
- the file name provided.
The final NUL is included in the sizeof. A bit of overhead
due to the format elements compensates for possible negative
numbers. */
size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
buf = alloca (buflen);
__snprintf (buf, buflen, procfd, fd, file);
file = buf;
}
INTERNAL_SYSCALL_DECL (err);
# if __ASSUME_LCHOWN_SYSCALL
if (flag & AT_SYMLINK_NOFOLLOW)
result = INTERNAL_SYSCALL (lchown, err, 3, file, owner, group);
else
result = INTERNAL_SYSCALL (chown, err, 3, file, owner, group);
# else
char link[PATH_MAX + 2];
char path[2 * PATH_MAX + 4];
int loopct;
size_t filelen;
static int libc_old_chown = 0 /* -1=old linux, 1=new linux, 0=unknown */;
if (libc_old_chown == 1)
{
if (flag & AT_SYMLINK_NOFOLLOW)
result = INTERNAL_SYSCALL (lchown, err, 3, __ptrvalue (file), owner,
group);
else
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
goto out;
}
# ifdef __NR_lchown
if (flag & AT_SYMLINK_NOFOLLOW)
{
result = INTERNAL_SYSCALL (lchown, err, 3, __ptrvalue (file), owner,
group);
goto out;
}
if (libc_old_chown == 0)
{
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
if (__builtin_expect (!INTERNAL_SYSCALL_ERROR_P (result, err), 1))
return result;
if (INTERNAL_SYSCALL_ERRNO (result, err) != ENOSYS)
{
libc_old_chown = 1;
goto fail;
}
libc_old_chown = -1;
}
# else
if (flag & AT_SYMLINK_NOFOLLOW)
{
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
goto out;
}
# endif
result = __readlink (file, link, PATH_MAX + 1);
if (result == -1)
{
# ifdef __NR_lchown
result = INTERNAL_SYSCALL (lchown, err, 3, __ptrvalue (file), owner,
group);
# else
result = INTERNAL_SYSCALL (chown, err, 3, __ptrvalue (file), owner,
group);
# endif
goto out;
}
filelen = strlen (file) + 1;
if (filelen > sizeof (path))
{
errno = ENAMETOOLONG;
return -1;
}
memcpy (path, file, filelen);
/* 'The system has an arbitrary limit...' In practise, we'll hit
ENAMETOOLONG before this, usually. */
for (loopct = 0; loopct < 128; ++loopct)
{
size_t linklen;
if (result >= PATH_MAX + 1)
{
errno = ENAMETOOLONG;
return -1;
}
link[result] = 0; /* Null-terminate string, just-in-case. */
linklen = strlen (link) + 1;
if (link[0] == '/')
memcpy (path, link, linklen);
else
{
filelen = strlen (path);
while (filelen > 1 && path[filelen - 1] == '/')
--filelen;
while (filelen > 0 && path[filelen - 1] != '/')
--filelen;
if (filelen + linklen > sizeof (path))
{
errno = ENAMETOOLONG;
return -1;
}
memcpy (path + filelen, link, linklen);
}
result = __readlink (path, link, PATH_MAX + 1);
if (result == -1)
{
# ifdef __NR_lchown
result = INTERNAL_SYSCALL (lchown, err, 3, path, owner, group);
# else
result = INTERNAL_SYSCALL (chown, err, 3, path, owner, group);
# endif
goto out;
}
}
__set_errno (ELOOP);
return -1;
out:
# endif
if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
{
# if !__ASSUME_LCHOWN_SYSCALL
fail:
# endif
__atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
result = -1;
}
return result;
#endif
}
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