fs/ext4/symlink.c

   1 /*
   2  *  linux/fs/ext4/symlink.c
   3  *
   4  * Only fast symlinks left here - the rest is done by generic code. AV, 1999
   5  *
   6  * Copyright (C) 1992, 1993, 1994, 1995
   7  * Remy Card (card@masi.ibp.fr)
   8  * Laboratoire MASI - Institut Blaise Pascal
   9  * Universite Pierre et Marie Curie (Paris VI)
  10  *
  11  *  from
  12  *
  13  *  linux/fs/minix/symlink.c
  14  *
  15  *  Copyright (C) 1991, 1992  Linus Torvalds
  16  *
  17  *  ext4 symlink handling code
  18  */
  19
  20 #include <linux/fs.h>
  21 #include <linux/namei.h>
  22 #include "ext4.h"
  23 #include "xattr.h"
  24
  25 #ifdef CONFIG_EXT4_FS_ENCRYPTION
  26 static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd)
  27 {
  28         struct page *cpage = NULL;
  29         char *caddr, *paddr = NULL;
  30         struct ext4_str cstr, pstr;
  31         struct inode *inode = d_inode(dentry);
  32         struct ext4_encrypted_symlink_data *sd;
  33         loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
  34         int res;
  35         u32 plen, max_size = inode->i_sb->s_blocksize;
  36
  37         if (!ext4_encrypted_inode(inode))
  38                 return page_follow_link_light(dentry, nd);
  39
  40         res = ext4_get_encryption_info(inode);
  41         if (res)
  42                 return ERR_PTR(res);
  43
  44         if (ext4_inode_is_fast_symlink(inode)) {
  45                 caddr = (char *) EXT4_I(inode)->i_data;
  46                 max_size = sizeof(EXT4_I(inode)->i_data);
  47         } else {
  48                 cpage = read_mapping_page(inode->i_mapping, 0, NULL);
  49                 if (IS_ERR(cpage))
  50                         return cpage;
  51                 caddr = kmap(cpage);
  52                 caddr[size] = 0;
  53         }
  54
  55         /* Symlink is encrypted */
  56         sd = (struct ext4_encrypted_symlink_data *)caddr;
  57         cstr.name = sd->encrypted_path;
  58         cstr.len  = le32_to_cpu(sd->len);
  59         if ((cstr.len +
  60              sizeof(struct ext4_encrypted_symlink_data) - 1) >
  61             max_size) {
  62                 /* Symlink data on the disk is corrupted */
  63                 res = -EIO;
  64                 goto errout;
  65         }
  66         plen = (cstr.len < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) ?
  67                 EXT4_FNAME_CRYPTO_DIGEST_SIZE*2 : cstr.len;
  68         paddr = kmalloc(plen + 1, GFP_NOFS);
  69         if (!paddr) {
  70                 res = -ENOMEM;
  71                 goto errout;
  72         }
  73         pstr.name = paddr;
  74         pstr.len = plen;
  75         res = _ext4_fname_disk_to_usr(inode, NULL, &cstr, &pstr);
  76         if (res < 0)
  77                 goto errout;
  78         /* Null-terminate the name */
  79         if (res <= plen)
  80                 paddr[res] = '\0';
  81         nd_set_link(nd, paddr);
  82         if (cpage) {
  83                 kunmap(cpage);
  84                 page_cache_release(cpage);
  85         }
  86         return NULL;
  87 errout:
  88         if (cpage) {
  89                 kunmap(cpage);
  90                 page_cache_release(cpage);
  91         }
  92         kfree(paddr);
  93         return ERR_PTR(res);
  94 }
  95
  96 static void ext4_put_link(struct dentry *dentry, struct nameidata *nd,
  97                           void *cookie)
  98 {
  99         struct page *page = cookie;
 100
 101         if (!page) {
 102                 kfree(nd_get_link(nd));
 103         } else {
 104                 kunmap(page);
 105                 page_cache_release(page);
 106         }
 107 }
 108 #endif
 109
 110 static void *ext4_follow_fast_link(struct dentry *dentry, struct nameidata *nd)
 111 {
 112         struct ext4_inode_info *ei = EXT4_I(d_inode(dentry));
 113         nd_set_link(nd, (char *) ei->i_data);
 114         return NULL;
 115 }
 116
 117 const struct inode_operations ext4_symlink_inode_operations = {
 118         .readlink       = generic_readlink,
 119 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 120         .follow_link    = ext4_follow_link,
 121         .put_link       = ext4_put_link,
 122 #else
 123         .follow_link    = page_follow_link_light,
 124         .put_link       = page_put_link,
 125 #endif
 126         .setattr        = ext4_setattr,
 127         .setxattr       = generic_setxattr,
 128         .getxattr       = generic_getxattr,
 129         .listxattr      = ext4_listxattr,
 130         .removexattr    = generic_removexattr,
 131 };
 132
 133 const struct inode_operations ext4_fast_symlink_inode_operations = {
 134         .readlink       = generic_readlink,
 135         .follow_link    = ext4_follow_fast_link,
 136         .setattr        = ext4_setattr,
 137         .setxattr       = generic_setxattr,
 138         .getxattr       = generic_getxattr,
 139         .listxattr      = ext4_listxattr,
 140         .removexattr    = generic_removexattr,
 141 };