lib/renameat2.c

   1 /* Rename a file relative to open directories.
   2    Copyright (C) 2009-2017 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* written by Eric Blake and Paul Eggert */
  18
  19 #include <config.h>
  20
  21 #include "renameat2.h"
  22
  23 #include <errno.h>
  24 #include <stdio.h>
  25 #include <sys/stat.h>
  26 #include <unistd.h>
  27
  28 #ifdef __linux__
  29 # include <sys/syscall.h>
  30 #endif
  31
  32 static int
  33 errno_fail (int e)
  34 {
  35   errno = e;
  36   return -1;
  37 }
  38
  39 #if HAVE_RENAMEAT
  40
  41 # include <stdbool.h>
  42 # include <stdlib.h>
  43 # include <string.h>
  44
  45 # include "dirname.h"
  46 # include "openat.h"
  47
  48 #else
  49 # include "openat-priv.h"
  50
  51 static int
  52 rename_noreplace (char const *src, char const *dst)
  53 {
  54   /* This has a race between the call to lstat and the call to rename.  */
  55   struct stat st;
  56   return (lstat (dst, &st) == 0 || errno == EOVERFLOW ? errno_fail (EEXIST)
  57           : errno == ENOENT ? rename (src, dst)
  58           : -1);
  59 }
  60 #endif
  61
  62 #undef renameat
  63
  64 /* Rename FILE1, in the directory open on descriptor FD1, to FILE2, in
  65    the directory open on descriptor FD2.  If possible, do it without
  66    changing the working directory.  Otherwise, resort to using
  67    save_cwd/fchdir, then rename/restore_cwd.  If either the save_cwd or
  68    the restore_cwd fails, then give a diagnostic and exit nonzero.
  69
  70    Obey FLAGS when doing the renaming.  If FLAGS is zero, this
  71    function is equivalent to renameat (FD1, SRC, FD2, DST).  */
  72
  73 int
  74 renameat2 (int fd1, char const *src, int fd2, char const *dst,
  75            unsigned int flags)
  76 {
  77 #ifdef SYS_renameat2
  78   int r = syscall (SYS_renameat2, fd1, src, fd2, dst, flags);
  79   if (! (r < 0 && (errno == ENOSYS || errno == EINVAL)))
  80     return r;
  81 #endif
  82
  83 #if HAVE_RENAMEAT
  84   {
  85   size_t src_len;
  86   size_t dst_len;
  87   char *src_temp = (char *) src;
  88   char *dst_temp = (char *) dst;
  89   bool src_slash;
  90   bool dst_slash;
  91   int ret_val;
  92   int rename_errno = ENOTDIR;
  93   struct stat src_st;
  94   struct stat dst_st;
  95   bool dst_found_nonexistent = false;
  96
  97   if (flags != 0)
  98     {
  99       /* RENAME_NOREPLACE is the only flag currently supported.  */
 100       if (flags & ~RENAME_NOREPLACE)
 101         return errno_fail (ENOTSUP);
 102       else
 103         {
 104           /* This has a race between the call to lstatat and the calls to
 105              renameat below.  */
 106           if (lstatat (fd2, dst, &dst_st) == 0 || errno == EOVERFLOW)
 107             return errno_fail (EEXIST);
 108           if (errno != ENOENT)
 109             return -1;
 110           dst_found_nonexistent = true;
 111         }
 112     }
 113
 114   /* Let strace see any ENOENT failure.  */
 115   src_len = strlen (src);
 116   dst_len = strlen (dst);
 117   if (!src_len || !dst_len)
 118     return renameat (fd1, src, fd2, dst);
 119
 120   src_slash = src[src_len - 1] == '/';
 121   dst_slash = dst[dst_len - 1] == '/';
 122   if (!src_slash && !dst_slash)
 123     return renameat (fd1, src, fd2, dst);
 124
 125   /* Presence of a trailing slash requires directory semantics.  If
 126      the source does not exist, or if the destination cannot be turned
 127      into a directory, give up now.  Otherwise, strip trailing slashes
 128      before calling rename.  */
 129   if (lstatat (fd1, src, &src_st))
 130     return -1;
 131   if (dst_found_nonexistent)
 132     {
 133       if (!S_ISDIR (src_st.st_mode))
 134         return errno_fail (ENOENT);
 135     }
 136   else if (lstatat (fd2, dst, &dst_st))
 137     {
 138       if (errno != ENOENT || !S_ISDIR (src_st.st_mode))
 139         return -1;
 140     }
 141   else if (!S_ISDIR (dst_st.st_mode))
 142     return errno_fail (ENOTDIR);
 143   else if (!S_ISDIR (src_st.st_mode))
 144     return errno_fail (EISDIR);
 145
 146 # if RENAME_TRAILING_SLASH_SOURCE_BUG
 147   /* See the lengthy comment in rename.c why Solaris 9 is forced to
 148      GNU behavior, while Solaris 10 is left with POSIX behavior,
 149      regarding symlinks with trailing slash.  */
 150   ret_val = -1;
 151   if (src_slash)
 152     {
 153       src_temp = strdup (src);
 154       if (!src_temp)
 155         {
 156           /* Rather than rely on strdup-posix, we set errno ourselves.  */
 157           rename_errno = ENOMEM;
 158           goto out;
 159         }
 160       strip_trailing_slashes (src_temp);
 161       if (lstatat (fd1, src_temp, &src_st))
 162         {
 163           rename_errno = errno;
 164           goto out;
 165         }
 166       if (S_ISLNK (src_st.st_mode))
 167         goto out;
 168     }
 169   if (dst_slash)
 170     {
 171       dst_temp = strdup (dst);
 172       if (!dst_temp)
 173         {
 174           rename_errno = ENOMEM;
 175           goto out;
 176         }
 177       strip_trailing_slashes (dst_temp);
 178       if (lstatat (fd2, dst_temp, &dst_st))
 179         {
 180           if (errno != ENOENT)
 181             {
 182               rename_errno = errno;
 183               goto out;
 184             }
 185         }
 186       else if (S_ISLNK (dst_st.st_mode))
 187         goto out;
 188     }
 189 # endif /* RENAME_TRAILING_SLASH_SOURCE_BUG */
 190
 191   /* renameat does not honor trailing / on Solaris 10.  Solve it in a
 192      similar manner to rename.  No need to worry about bugs not present
 193      on Solaris, since all other systems either lack renameat or honor
 194      trailing slash correctly.  */
 195
 196   ret_val = renameat (fd1, src_temp, fd2, dst_temp);
 197   rename_errno = errno;
 198   goto out;
 199  out:
 200   if (src_temp != src)
 201     free (src_temp);
 202   if (dst_temp != dst)
 203     free (dst_temp);
 204   errno = rename_errno;
 205   return ret_val;
 206   }
 207 #else /* !HAVE_RENAMEAT */
 208
 209   /* RENAME_NOREPLACE is the only flag currently supported.  */
 210   if (flags & ~RENAME_NOREPLACE)
 211     return errno_fail (ENOTSUP);
 212   return at_func2 (fd1, src, fd2, dst, flags ? rename_noreplace : rename);
 213
 214 #endif /* !HAVE_RENAMEAT */
 215 }