sysdeps/unix/sysv/linux/fchownat.c

   1 /* Copyright (C) 2005 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
  29 /* Change the owner and group of FILE.  */
  30 int
  31 fchownat (fd, file, owner, group, flag)
  32      int fd;
  33      const char *file;
  34      uid_t owner;
  35      gid_t group;
  36      int flag;
  37 {
  38   if (flag & ~AT_SYMLINK_NOFOLLOW)
  39     {
  40       __set_errno (EINVAL);
  41       return -1;
  42     }
  43
  44   char *buf = NULL;
  45
  46   if (fd != AT_FDCWD && file[0] != '/')
  47     {
  48       size_t filelen = strlen (file);
  49       static const char procfd[] = "/proc/self/fd/%d/%s";
  50       /* Buffer for the path name we are going to use.  It consists of
  51          - the string /proc/self/fd/
  52          - the file descriptor number
  53          - the file name provided.
  54          The final NUL is included in the sizeof.   A bit of overhead
  55          due to the format elements compensates for possible negative
  56          numbers.  */
  57       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  58       buf = alloca (buflen);
  59
  60       __snprintf (buf, buflen, procfd, fd, file);
  61       file = buf;
  62     }
  63
  64   int result;
  65   INTERNAL_SYSCALL_DECL (err);
  66
  67   if (flag & AT_SYMLINK_NOFOLLOW)
  68     result = INTERNAL_SYSCALL (lchown, err, 3, file, owner, group);
  69   else
  70     result = INTERNAL_SYSCALL (chown, err, 3, file, owner, group);
  71
  72   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
  73     {
  74       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
  75       result = -1;
  76     }
  77
  78   return result;
  79 }