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/* chown() compatibility.
Copyright (C) 1998, 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, see
<http://www.gnu.org/licenses/>. */
#include <errno.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
__chown (const char *file, uid_t owner, gid_t group)
{
#if __ASSUME_LCHOWN_SYSCALL
return INLINE_SYSCALL (chown, 3, file, owner, group);
#else
int err;
int old_errno;
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)
return INLINE_SYSCALL (chown, 3, __ptrvalue (file), owner, group);
old_errno = errno;
# ifdef __NR_lchown
if (libc_old_chown == 0)
{
err = INLINE_SYSCALL (chown, 3, __ptrvalue (file), owner, group);
if (err != -1 || errno != ENOSYS)
{
libc_old_chown = 1;
return err;
}
libc_old_chown = -1;
}
# endif
err = __readlink (file, link, PATH_MAX + 1);
if (err == -1)
{
__set_errno (old_errno);
return __lchown (file, owner, group);
}
filelen = strlen (file) + 1;
if (filelen > sizeof (path))
{
__set_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 (err >= PATH_MAX + 1)
{
__set_errno (ENAMETOOLONG);
return -1;
}
link[err] = 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);
}
err = __readlink (path, link, PATH_MAX + 1);
if (err == -1)
{
__set_errno (old_errno);
return __lchown (path, owner, group);
}
}
__set_errno (ELOOP);
return -1;
#endif
}
libc_hidden_def (__chown)
#include <shlib-compat.h>
versioned_symbol (libc, __chown, chown, GLIBC_2_1);
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