sysdeps/unix/sysv/linux/i386/fchownat.c

   1 /* Copyright (C) 2005-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <fcntl.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23
  24 #include <sysdep.h>
  25 #include <sys/syscall.h>
  26 #include <shlib-compat.h>
  27
  28 #include <linux/posix_types.h>
  29 #include <kernel-features.h>
  30
  31
  32 int
  33 fchownat (int fd, const char *file, uid_t owner, gid_t group, int flag)
  34 {
  35   int result;
  36
  37 #ifdef __NR_fchownat
  38 # ifndef __ASSUME_ATFCTS
  39   if (__have_atfcts >= 0)
  40 # endif
  41     {
  42       result = INLINE_SYSCALL (fchownat, 5, fd, file, owner, group, flag);
  43 # ifndef __ASSUME_ATFCTS
  44       if (result == -1 && errno == ENOSYS)
  45         __have_atfcts = -1;
  46       else
  47 # endif
  48         return result;
  49     }
  50 #endif
  51
  52 #ifndef __ASSUME_ATFCTS
  53   if (flag & ~AT_SYMLINK_NOFOLLOW)
  54     {
  55       __set_errno (EINVAL);
  56       return -1;
  57     }
  58
  59   char *buf = NULL;
  60
  61   if (fd != AT_FDCWD && file[0] != '/')
  62     {
  63       size_t filelen = strlen (file);
  64       if (__builtin_expect (filelen == 0, 0))
  65         {
  66           __set_errno (ENOENT);
  67           return -1;
  68         }
  69
  70       static const char procfd[] = "/proc/self/fd/%d/%s";
  71       /* Buffer for the path name we are going to use.  It consists of
  72          - the string /proc/self/fd/
  73          - the file descriptor number
  74          - the file name provided.
  75          The final NUL is included in the sizeof.   A bit of overhead
  76          due to the format elements compensates for possible negative
  77          numbers.  */
  78       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  79       buf = alloca (buflen);
  80
  81       __snprintf (buf, buflen, procfd, fd, file);
  82       file = buf;
  83     }
  84
  85   INTERNAL_SYSCALL_DECL (err);
  86
  87   if (flag & AT_SYMLINK_NOFOLLOW)
  88     result = INTERNAL_SYSCALL (lchown32, err, 3, file, owner, group);
  89   else
  90     result = INTERNAL_SYSCALL (chown32, err, 3, file, owner, group);
  91
  92   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
  93     {
  94       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
  95       return -1;
  96     }
  97
  98   return result;
  99
 100 #endif
 101 }