sysdeps/unix/sysv/linux/fchownat.c

   1 /* Copyright (C) 2005, 2006 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <stddef.h>
  22 #include <stdio.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <sys/types.h>
  26 #include <alloca.h>
  27 #include <sysdep.h>
  28 #include <kernel-features.h>
  29
  30
  31 /* Change the owner and group of FILE.  */
  32 int
  33 fchownat (fd, file, owner, group, flag)
  34      int fd;
  35      const char *file;
  36      uid_t owner;
  37      gid_t group;
  38      int flag;
  39 {
  40   int result;
  41
  42 #ifdef __NR_fchownat
  43 # ifndef __ASSUME_ATFCTS
  44   if (__have_atfcts >= 0)
  45 # endif
  46     {
  47       result = INLINE_SYSCALL (fchownat, 5, fd, file, owner, group, flag);
  48 # ifndef __ASSUME_ATFCTS
  49       if (result == -1 && errno == ENOSYS)
  50         __have_atfcts = -1;
  51       else
  52 # endif
  53         return result;
  54     }
  55 #endif
  56
  57 #ifndef __ASSUME_ATFCTS
  58   if (flag & ~AT_SYMLINK_NOFOLLOW)
  59     {
  60       __set_errno (EINVAL);
  61       return -1;
  62     }
  63
  64   char *buf = NULL;
  65
  66   if (fd != AT_FDCWD && file[0] != '/')
  67     {
  68       size_t filelen = strlen (file);
  69       static const char procfd[] = "/proc/self/fd/%d/%s";
  70       /* Buffer for the path name we are going to use.  It consists of
  71          - the string /proc/self/fd/
  72          - the file descriptor number
  73          - the file name provided.
  74          The final NUL is included in the sizeof.   A bit of overhead
  75          due to the format elements compensates for possible negative
  76          numbers.  */
  77       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  78       buf = alloca (buflen);
  79
  80       __snprintf (buf, buflen, procfd, fd, file);
  81       file = buf;
  82     }
  83
  84   INTERNAL_SYSCALL_DECL (err);
  85
  86   if (flag & AT_SYMLINK_NOFOLLOW)
  87     result = INTERNAL_SYSCALL (lchown, err, 3, file, owner, group);
  88   else
  89     result = INTERNAL_SYSCALL (chown, err, 3, file, owner, group);
  90
  91   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
  92     {
  93       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
  94       result = -1;
  95     }
  96
  97   return result;
  98 #endif
  99 }