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 const char *ext4_encrypted_follow_link(struct dentry *dentry, void **cookie)
  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         res = ext4_get_encryption_info(inode);
  38         if (res)
  39                 return ERR_PTR(res);
  40
  41         if (ext4_inode_is_fast_symlink(inode)) {
  42                 caddr = (char *) EXT4_I(inode)->i_data;
  43                 max_size = sizeof(EXT4_I(inode)->i_data);
  44         } else {
  45                 cpage = read_mapping_page(inode->i_mapping, 0, NULL);
  46                 if (IS_ERR(cpage))
  47                         return ERR_CAST(cpage);
  48                 caddr = kmap(cpage);
  49                 caddr[size] = 0;
  50         }
  51
  52         /* Symlink is encrypted */
  53         sd = (struct ext4_encrypted_symlink_data *)caddr;
  54         cstr.name = sd->encrypted_path;
  55         cstr.len  = le16_to_cpu(sd->len);
  56         if ((cstr.len +
  57              sizeof(struct ext4_encrypted_symlink_data) - 1) >
  58             max_size) {
  59                 /* Symlink data on the disk is corrupted */
  60                 res = -EFSCORRUPTED;
  61                 goto errout;
  62         }
  63         plen = (cstr.len < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) ?
  64                 EXT4_FNAME_CRYPTO_DIGEST_SIZE*2 : cstr.len;
  65         paddr = kmalloc(plen + 1, GFP_NOFS);
  66         if (!paddr) {
  67                 res = -ENOMEM;
  68                 goto errout;
  69         }
  70         pstr.name = paddr;
  71         pstr.len = plen;
  72         res = _ext4_fname_disk_to_usr(inode, NULL, &cstr, &pstr);
  73         if (res < 0)
  74                 goto errout;
  75         /* Null-terminate the name */
  76         if (res <= plen)
  77                 paddr[res] = '\0';
  78         if (cpage) {
  79                 kunmap(cpage);
  80                 page_cache_release(cpage);
  81         }
  82         return *cookie = paddr;
  83 errout:
  84         if (cpage) {
  85                 kunmap(cpage);
  86                 page_cache_release(cpage);
  87         }
  88         kfree(paddr);
  89         return ERR_PTR(res);
  90 }
  91
  92 const struct inode_operations ext4_encrypted_symlink_inode_operations = {
  93         .readlink       = generic_readlink,
  94         .follow_link    = ext4_encrypted_follow_link,
  95         .put_link       = kfree_put_link,
  96         .setattr        = ext4_setattr,
  97         .setxattr       = generic_setxattr,
  98         .getxattr       = generic_getxattr,
  99         .listxattr      = ext4_listxattr,
 100         .removexattr    = generic_removexattr,
 101 };
 102 #endif
 103
 104 const struct inode_operations ext4_symlink_inode_operations = {
 105         .readlink       = generic_readlink,
 106         .follow_link    = page_follow_link_light,
 107         .put_link       = page_put_link,
 108         .setattr        = ext4_setattr,
 109         .setxattr       = generic_setxattr,
 110         .getxattr       = generic_getxattr,
 111         .listxattr      = ext4_listxattr,
 112         .removexattr    = generic_removexattr,
 113 };
 114
 115 const struct inode_operations ext4_fast_symlink_inode_operations = {
 116         .readlink       = generic_readlink,
 117         .follow_link    = simple_follow_link,
 118         .setattr        = ext4_setattr,
 119         .setxattr       = generic_setxattr,
 120         .getxattr       = generic_getxattr,
 121         .listxattr      = ext4_listxattr,
 122         .removexattr    = generic_removexattr,
 123 };