LCOV - code coverage report
Current view: top level - lkbce/fs/configfs - symlink.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 176 176 100.0 %
Date: 2017-01-25 Functions: 11 11 100.0 %

          Line data    Source code
       1             : /* -*- mode: c; c-basic-offset: 8; -*-
       2             :  * vim: noexpandtab sw=8 ts=8 sts=0:
       3             :  *
       4             :  * symlink.c - operations for configfs symlinks.
       5             :  *
       6             :  * This program is free software; you can redistribute it and/or
       7             :  * modify it under the terms of the GNU General Public
       8             :  * License as published by the Free Software Foundation; either
       9             :  * version 2 of the License, or (at your option) any later version.
      10             :  *
      11             :  * This program is distributed in the hope that it will be useful,
      12             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      13             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14             :  * General Public License for more details.
      15             :  *
      16             :  * You should have received a copy of the GNU General Public
      17             :  * License along with this program; if not, write to the
      18             :  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
      19             :  * Boston, MA 021110-1307, USA.
      20             :  *
      21             :  * Based on sysfs:
      22             :  *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
      23             :  *
      24             :  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
      25             :  */
      26             : 
      27             : #include <linux/fs.h>
      28             : #include <linux/module.h>
      29             : #include <linux/namei.h>
      30             : 
      31             : #include <linux/configfs.h>
      32             : #include "configfs_internal.h"
      33             : 
      34             : /* Protects attachments of new symlinks */
      35           1 : DEFINE_MUTEX(configfs_symlink_mutex);
      36             : 
      37             : static int item_depth(struct config_item * item)
      38             : {
      39           2 :         struct config_item * p = item;
      40           2 :         int depth = 0;
      41          10 :         do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
      42           2 :         return depth;
      43           1 : }
      44             : 
      45             : static int item_path_length(struct config_item * item)
      46           1 : {
      47           2 :         struct config_item * p = item;
      48           2 :         int length = 1;
      49           2 :         do {
      50           5 :                 length += strlen(config_item_name(p)) + 1;
      51           3 :                 p = p->ci_parent;
      52           6 :         } while (p && !configfs_is_root(p));
      53           2 :         return length;
      54           1 : }
      55             : 
      56             : static void fill_item_path(struct config_item * item, char * buffer, int length)
      57           1 : {
      58           1 :         struct config_item * p;
      59           1 : 
      60           2 :         --length;
      61          10 :         for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
      62           7 :                 int cur = strlen(config_item_name(p));
      63           3 : 
      64             :                 /* back up enough to print this bus id with '/' */
      65           1 :                 length -= cur;
      66           4 :                 strncpy(buffer + length,config_item_name(p),cur);
      67           2 :                 *(buffer + --length) = '/';
      68           2 :         }
      69             : }
      70             : 
      71           1 : static int create_link(struct config_item *parent_item,
      72             :                        struct config_item *item,
      73             :                        struct dentry *dentry)
      74           1 : {
      75           3 :         struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
      76           1 :         struct configfs_symlink *sl;
      77           1 :         int ret;
      78           1 : 
      79           1 :         ret = -ENOENT;
      80           4 :         if (!configfs_dirent_is_ready(target_sd))
      81           1 :                 goto out;
      82           1 :         ret = -ENOMEM;
      83           3 :         sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
      84           2 :         if (sl) {
      85           2 :                 sl->sl_target = config_item_get(item);
      86           2 :                 spin_lock(&configfs_dirent_lock);
      87           2 :                 if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
      88           2 :                         spin_unlock(&configfs_dirent_lock);
      89           2 :                         config_item_put(item);
      90           1 :                         kfree(sl);
      91           1 :                         return -ENOENT;
      92             :                 }
      93           2 :                 list_add(&sl->sl_list, &target_sd->s_links);
      94           2 :                 spin_unlock(&configfs_dirent_lock);
      95           4 :                 ret = configfs_create_link(sl, parent_item->ci_dentry,
      96             :                                            dentry);
      97           2 :                 if (ret) {
      98           2 :                         spin_lock(&configfs_dirent_lock);
      99           2 :                         list_del_init(&sl->sl_list);
     100           2 :                         spin_unlock(&configfs_dirent_lock);
     101           2 :                         config_item_put(item);
     102           1 :                         kfree(sl);
     103             :                 }
     104             :         }
     105             : 
     106             : out:
     107           4 :         return ret;
     108             : }
     109             : 
     110           3 : 
     111             : static int get_target(const char *symname, struct path *path,
     112             :                       struct config_item **target)
     113           1 : {
     114             :         int ret;
     115             : 
     116           1 :         ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
     117           2 :         if (!ret) {
     118           3 :                 if (path->dentry->d_sb == configfs_sb) {
     119           2 :                         *target = configfs_get_config_item(path->dentry);
     120           2 :                         if (!*target) {
     121           1 :                                 ret = -ENOENT;
     122           1 :                                 path_put(path);
     123             :                         }
     124             :                 } else {
     125           1 :                         ret = -EPERM;
     126           1 :                         path_put(path);
     127             :                 }
     128             :         }
     129             : 
     130           2 :         return ret;
     131             : }
     132             : 
     133             : 
     134             : int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
     135             : {
     136           1 :         int ret;
     137           1 :         struct path path;
     138           1 :         struct configfs_dirent *sd;
     139           1 :         struct config_item *parent_item;
     140           2 :         struct config_item *target_item = NULL;
     141           1 :         struct config_item_type *type;
     142           1 : 
     143           1 :         ret = -EPERM;  /* What lack-of-symlink returns */
     144           4 :         if (dentry->d_parent == configfs_sb->s_root)
     145           1 :                 goto out;
     146             : 
     147           2 :         sd = dentry->d_parent->d_fsdata;
     148             :         /*
     149             :          * Fake invisibility if dir belongs to a group/default groups hierarchy
     150             :          * being attached
     151             :          */
     152           1 :         ret = -ENOENT;
     153           4 :         if (!configfs_dirent_is_ready(sd))
     154           1 :                 goto out;
     155             : 
     156           2 :         parent_item = configfs_get_config_item(dentry->d_parent);
     157           1 :         type = parent_item->ci_type;
     158             : 
     159           1 :         ret = -EPERM;
     160           8 :         if (!type || !type->ct_item_ops ||
     161             :             !type->ct_item_ops->allow_link)
     162           1 :                 goto out_put;
     163             : 
     164           3 :         ret = get_target(symname, &path, &target_item);
     165           2 :         if (ret)
     166           1 :                 goto out_put;
     167             : 
     168           1 :         ret = type->ct_item_ops->allow_link(parent_item, target_item);
     169           2 :         if (!ret) {
     170           1 :                 mutex_lock(&configfs_symlink_mutex);
     171           6 :                 ret = create_link(parent_item, target_item, dentry);
     172           1 :                 mutex_unlock(&configfs_symlink_mutex);
     173           5 :                 if (ret && type->ct_item_ops->drop_link)
     174           1 :                         type->ct_item_ops->drop_link(parent_item,
     175             :                                                      target_item);
     176             :         }
     177             : 
     178           4 :         config_item_put(target_item);
     179           1 :         path_put(&path);
     180             : 
     181           1 : out_put:
     182           6 :         config_item_put(parent_item);
     183             : 
     184           1 : out:
     185           3 :         return ret;
     186             : }
     187             : 
     188             : int configfs_unlink(struct inode *dir, struct dentry *dentry)
     189             : {
     190           3 :         struct configfs_dirent *sd = dentry->d_fsdata;
     191           1 :         struct configfs_symlink *sl;
     192           1 :         struct config_item *parent_item;
     193           1 :         struct config_item_type *type;
     194           1 :         int ret;
     195           1 : 
     196           1 :         ret = -EPERM;  /* What lack-of-symlink returns */
     197           2 :         if (!(sd->s_type & CONFIGFS_ITEM_LINK))
     198           1 :                 goto out;
     199             : 
     200           8 :         BUG_ON(dentry->d_parent == configfs_sb->s_root);
     201             : 
     202           2 :         sl = sd->s_element;
     203             : 
     204           2 :         parent_item = configfs_get_config_item(dentry->d_parent);
     205           1 :         type = parent_item->ci_type;
     206             : 
     207           2 :         spin_lock(&configfs_dirent_lock);
     208           2 :         list_del_init(&sd->s_sibling);
     209           2 :         spin_unlock(&configfs_dirent_lock);
     210           4 :         configfs_drop_dentry(sd, dentry->d_parent);
     211           1 :         dput(dentry);
     212           3 :         configfs_put(sd);
     213             : 
     214             :         /*
     215             :          * drop_link() must be called before
     216             :          * list_del_init(&sl->sl_list), so that the order of
     217             :          * drop_link(this, target) and drop_item(target) is preserved.
     218             :          */
     219           8 :         if (type && type->ct_item_ops &&
     220             :             type->ct_item_ops->drop_link)
     221           1 :                 type->ct_item_ops->drop_link(parent_item,
     222             :                                                sl->sl_target);
     223             : 
     224           2 :         spin_lock(&configfs_dirent_lock);
     225           2 :         list_del_init(&sl->sl_list);
     226           2 :         spin_unlock(&configfs_dirent_lock);
     227             : 
     228             :         /* Put reference from create_link() */
     229           2 :         config_item_put(sl->sl_target);
     230           1 :         kfree(sl);
     231             : 
     232           2 :         config_item_put(parent_item);
     233             : 
     234           1 :         ret = 0;
     235             : 
     236           1 : out:
     237           2 :         return ret;
     238             : }
     239             : 
     240             : static int configfs_get_target_path(struct config_item * item, struct config_item * target,
     241             :                                    char *path)
     242             : {
     243           1 :         char * s;
     244           1 :         int depth, size;
     245           1 : 
     246           4 :         depth = item_depth(item);
     247           5 :         size = item_path_length(target) + depth * 3 - 1;
     248           2 :         if (size > PATH_MAX)
     249           1 :                 return -ENAMETOOLONG;
     250             : 
     251             :         pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
     252             : 
     253           7 :         for (s = path; depth--; s += 3)
     254           2 :                 strcpy(s,"../");
     255           2 : 
     256           3 :         fill_item_path(target, path, size);
     257             :         pr_debug("%s: path = '%s'\n", __func__, path);
     258             : 
     259           1 :         return 0;
     260             : }
     261             : 
     262             : static int configfs_getlink(struct dentry *dentry, char * path)
     263             : {
     264           1 :         struct config_item *item, *target_item;
     265           2 :         int error = 0;
     266           1 : 
     267           2 :         item = configfs_get_config_item(dentry->d_parent);
     268           2 :         if (!item)
     269           1 :                 return -EINVAL;
     270             : 
     271           2 :         target_item = configfs_get_config_item(dentry);
     272           2 :         if (!target_item) {
     273           2 :                 config_item_put(item);
     274           1 :                 return -EINVAL;
     275             :         }
     276             : 
     277           1 :         down_read(&configfs_rename_sem);
     278           3 :         error = configfs_get_target_path(item, target_item, path);
     279           1 :         up_read(&configfs_rename_sem);
     280             : 
     281           2 :         config_item_put(item);
     282           2 :         config_item_put(target_item);
     283           1 :         return error;
     284             : 
     285             : }
     286             : 
     287             : static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
     288             : {
     289           2 :         int error = -ENOMEM;
     290           3 :         unsigned long page = get_zeroed_page(GFP_KERNEL);
     291           1 : 
     292           3 :         if (page) {
     293           4 :                 error = configfs_getlink(dentry, (char *)page);
     294           2 :                 if (!error) {
     295           2 :                         nd_set_link(nd, (char *)page);
     296           1 :                         return (void *)page;
     297             :                 }
     298             :         }
     299             : 
     300           6 :         nd_set_link(nd, ERR_PTR(error));
     301           1 :         return NULL;
     302             : }
     303             : 
     304             : static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
     305             :                               void *cookie)
     306           1 : {
     307           2 :         if (cookie) {
     308           1 :                 unsigned long page = (unsigned long)cookie;
     309           1 :                 free_page(page);
     310             :         }
     311           1 : }
     312             : 
     313           1 : const struct inode_operations configfs_symlink_inode_operations = {
     314             :         .follow_link = configfs_follow_link,
     315             :         .readlink = generic_readlink,
     316             :         .put_link = configfs_put_link,
     317             :         .setattr = configfs_setattr,
     318             : };
     319             : 

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