sysdeps/unix/sysv/linux/fchownat.c

   1 /* Copyright (C) 2005, 2006, 2009 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 <stddef.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <sys/types.h>
  25 #include <alloca.h>
  26 #include <sysdep.h>
  27 #include <kernel-features.h>
  28
  29
  30 /* Change the owner and group of FILE.  */
  31 int
  32 fchownat (fd, file, owner, group, flag)
  33      int fd;
  34      const char *file;
  35      uid_t owner;
  36      gid_t group;
  37      int flag;
  38 {
  39   int result;
  40
  41 #ifdef __NR_fchownat
  42 # ifndef __ASSUME_ATFCTS
  43   if (__have_atfcts >= 0)
  44 # endif
  45     {
  46       result = INLINE_SYSCALL (fchownat, 5, fd, file, owner, group, flag);
  47 # ifndef __ASSUME_ATFCTS
  48       if (result == -1 && errno == ENOSYS)
  49         __have_atfcts = -1;
  50       else
  51 # endif
  52         return result;
  53     }
  54 #endif
  55
  56 #ifndef __ASSUME_ATFCTS
  57   if (flag & ~AT_SYMLINK_NOFOLLOW)
  58     {
  59       __set_errno (EINVAL);
  60       return -1;
  61     }
  62
  63   char *buf = NULL;
  64
  65   if (fd != AT_FDCWD && file[0] != '/')
  66     {
  67       size_t filelen = strlen (file);
  68       if (__builtin_expect (filelen == 0, 0))
  69         {
  70           __set_errno (ENOENT);
  71           return -1;
  72         }
  73
  74       static const char procfd[] = "/proc/self/fd/%d/%s";
  75       /* Buffer for the path name we are going to use.  It consists of
  76          - the string /proc/self/fd/
  77          - the file descriptor number
  78          - the file name provided.
  79          The final NUL is included in the sizeof.   A bit of overhead
  80          due to the format elements compensates for possible negative
  81          numbers.  */
  82       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
  83       buf = alloca (buflen);
  84
  85       __snprintf (buf, buflen, procfd, fd, file);
  86       file = buf;
  87     }
  88
  89   INTERNAL_SYSCALL_DECL (err);
  90
  91   if (flag & AT_SYMLINK_NOFOLLOW)
  92     result = INTERNAL_SYSCALL (lchown, err, 3, file, owner, group);
  93   else
  94     result = INTERNAL_SYSCALL (chown, err, 3, file, owner, group);
  95
  96   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
  97     {
  98       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
  99       result = -1;
 100     }
 101
 102   return result;
 103 #endif
 104 }