fsal_symlinks.c

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/*
 * vim:expandtab:shiftwidth=8:tabstop=8:
 *
 * Copyright CEA/DAM/DIF  (2008)
 * contributeur : Philippe DENIEL   philippe.deniel@cea.fr
 *                Thomas LEIBOVICI  thomas.leibovici@cea.fr
 *
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * ------------- 
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "fsal.h"
#include "fsal_internal.h"
#include "FSAL/access_check.h"
#include "fsal_convert.h"
#include <string.h>
#include <unistd.h>

fsal_status_t VFSFSAL_readlink(fsal_handle_t * p_linkhandle,       /* IN */
                            fsal_op_context_t * p_context,      /* IN */
                            fsal_path_t * p_link_content,       /* OUT */
                            fsal_attrib_list_t * p_link_attributes      /* [ IN/OUT ] */
    )
{

  int rc, errsv;
  fsal_status_t status;
  char link_content_out[FSAL_MAX_PATH_LEN];

  /* sanity checks.
   * note : link_attributes is optional.
   */
  if(!p_linkhandle || !p_context || !p_link_content)
    Return(ERR_FSAL_FAULT, 0, INDEX_FSAL_readlink);

  memset(link_content_out, 0, FSAL_MAX_PATH_LEN);

  /* Read the link on the filesystem */
  TakeTokenFSCall();
  rc = vfs_readlink_by_handle(((vfsfsal_op_context_t *)p_context)->export_context->mount_root_fd,
                              &((vfsfsal_handle_t *)p_linkhandle)->data.vfs_handle,
                               link_content_out,
                               FSAL_MAX_PATH_LEN ) ;
  errsv = errno;
  ReleaseTokenFSCall();

  if( rc == -1 )
    Return(posix2fsal_error(errsv), errsv, INDEX_FSAL_readlink);

  /* convert char * to fsal_path_t */
  status = FSAL_str2path(link_content_out, FSAL_MAX_PATH_LEN, p_link_content);

  if(FSAL_IS_ERROR(status))
    ReturnStatus(status, INDEX_FSAL_readlink);

  /* retrieves object attributes, if asked */

  if(p_link_attributes)
    {

      status = VFSFSAL_getattrs(p_linkhandle, p_context, p_link_attributes);

      /* On error, we set a flag in the returned attributes */

      if(FSAL_IS_ERROR(status))
        {
          FSAL_CLEAR_MASK(p_link_attributes->asked_attributes);
          FSAL_SET_MASK(p_link_attributes->asked_attributes, FSAL_ATTR_RDATTR_ERR);
        }

    }

  Return(ERR_FSAL_NO_ERROR, 0, INDEX_FSAL_readlink);

}

fsal_status_t VFSFSAL_symlink(fsal_handle_t * p_parent_directory_handle,   /* IN */
                           fsal_name_t * p_linkname,    /* IN */
                           fsal_path_t * p_linkcontent, /* IN */
                           fsal_op_context_t * p_context,       /* IN */
                           fsal_accessmode_t accessmode,        /* IN (ignored) */
                           fsal_handle_t * p_link_handle,       /* OUT */
                           fsal_attrib_list_t * p_link_attributes       /* [ IN/OUT ] */
    )
{

  int rc, errsv;
  fsal_status_t status;
  int fd;
  struct stat buffstat;
  int setgid_bit = FALSE;

  /* sanity checks.
   * note : link_attributes is optional.
   */
  if(!p_parent_directory_handle || !p_context ||
     !p_link_handle || !p_linkname || !p_linkcontent)
    Return(ERR_FSAL_FAULT, 0, INDEX_FSAL_symlink);

  /* Tests if symlinking is allowed by configuration. */

  if(!global_fs_info.symlink_support)
    Return(ERR_FSAL_NOTSUPP, 0, INDEX_FSAL_symlink);

  TakeTokenFSCall();
  status =
      fsal_internal_handle2fd(p_context, p_parent_directory_handle, &fd,
                              O_RDONLY | O_DIRECTORY);
  ReleaseTokenFSCall();

  if(FSAL_IS_ERROR(status))
    ReturnStatus(status, INDEX_FSAL_symlink);

  /* retrieve directory metadata, for checking access */
  TakeTokenFSCall();
  rc = fstat(fd, &buffstat);
  errsv = errno;
  ReleaseTokenFSCall();

  if(rc)
    {
      close(fd);

      if(errsv == ENOENT)
        Return(ERR_FSAL_STALE, errsv, INDEX_FSAL_symlink);
      else
        Return(posix2fsal_error(errsv), errsv, INDEX_FSAL_symlink);
    }

  if(buffstat.st_mode & S_ISGID)
    setgid_bit = TRUE;

  status = fsal_check_access(p_context, FSAL_W_OK, &buffstat, NULL);
  if(FSAL_IS_ERROR(status))
    ReturnStatus(status, INDEX_FSAL_symlink);

  /* build symlink path */

  /* create the symlink on the filesystem. */

  TakeTokenFSCall();
  rc = symlinkat(p_linkcontent->path, fd, p_linkname->name);
  errsv = errno;
  ReleaseTokenFSCall();

  if(rc)
    {
      close(fd);
      Return(posix2fsal_error(errsv), errsv, INDEX_FSAL_symlink);
    }

  /* now get the associated handle, while there is a race, there is
     also a race lower down  */
  status = fsal_internal_get_handle_at(fd, p_linkname->name, p_link_handle);

  if(FSAL_IS_ERROR(status))
    {
      close(fd);
      ReturnStatus(status, INDEX_FSAL_symlink);
    }

  /* chown the symlink to the current user/group */
  TakeTokenFSCall();
  rc = fchownat(fd, p_linkname->name, ((vfsfsal_op_context_t *)p_context)->credential.user,
                setgid_bit ? -1 : ((vfsfsal_op_context_t *)p_context)->credential.group,
                AT_SYMLINK_NOFOLLOW);
  errsv = errno;
  ReleaseTokenFSCall();

  close(fd);

  if(rc)
    Return(posix2fsal_error(errsv), errsv, INDEX_FSAL_symlink);

  /* get attributes if asked */

  if(p_link_attributes)
    {

      status = VFSFSAL_getattrs(p_link_handle, p_context, p_link_attributes);

      /* On error, we set a flag in the returned attributes */

      if(FSAL_IS_ERROR(status))
        {
          FSAL_CLEAR_MASK(p_link_attributes->asked_attributes);
          FSAL_SET_MASK(p_link_attributes->asked_attributes, FSAL_ATTR_RDATTR_ERR);
        }

    }

  /* OK */
  Return(ERR_FSAL_NO_ERROR, 0, INDEX_FSAL_symlink);
}