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_fname_crypto_ctx *ctx = NULL;
  33         struct ext4_encrypted_symlink_data *sd;
  34         loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
  35         int res;
  36         u32 plen, max_size = inode->i_sb->s_blocksize;
  37
  38         if (!ext4_encrypted_inode(inode))
  39                 return page_follow_link_light(dentry, nd);
  40
  41         ctx = ext4_get_fname_crypto_ctx(inode, inode->i_sb->s_blocksize);
  42         if (IS_ERR(ctx))
  43                 return ctx;
  44
  45         if (ext4_inode_is_fast_symlink(inode)) {
  46                 caddr = (char *) EXT4_I(inode)->i_data;
  47                 max_size = sizeof(EXT4_I(inode)->i_data);
  48         } else {
  49                 cpage = read_mapping_page(inode->i_mapping, 0, NULL);
  50                 if (IS_ERR(cpage)) {
  51                         ext4_put_fname_crypto_ctx(&ctx);
  52                         return cpage;
  53                 }
  54                 caddr = kmap(cpage);
  55                 caddr[size] = 0;
  56         }
  57
  58         /* Symlink is encrypted */
  59         sd = (struct ext4_encrypted_symlink_data *)caddr;
  60         cstr.name = sd->encrypted_path;
  61         cstr.len  = le32_to_cpu(sd->len);
  62         if ((cstr.len +
  63              sizeof(struct ext4_encrypted_symlink_data) - 1) >
  64             max_size) {
  65                 /* Symlink data on the disk is corrupted */
  66                 res = -EIO;
  67                 goto errout;
  68         }
  69         plen = (cstr.len < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) ?
  70                 EXT4_FNAME_CRYPTO_DIGEST_SIZE*2 : cstr.len;
  71         paddr = kmalloc(plen + 1, GFP_NOFS);
  72         if (!paddr) {
  73                 res = -ENOMEM;
  74                 goto errout;
  75         }
  76         pstr.name = paddr;
  77         pstr.len = plen;
  78         res = _ext4_fname_disk_to_usr(ctx, NULL, &cstr, &pstr);
  79         if (res < 0)
  80                 goto errout;
  81         /* Null-terminate the name */
  82         if (res <= plen)
  83                 paddr[res] = '\0';
  84         nd_set_link(nd, paddr);
  85         ext4_put_fname_crypto_ctx(&ctx);
  86         if (cpage) {
  87                 kunmap(cpage);
  88                 page_cache_release(cpage);
  89         }
  90         return NULL;
  91 errout:
  92         ext4_put_fname_crypto_ctx(&ctx);
  93         if (cpage) {
  94                 kunmap(cpage);
  95                 page_cache_release(cpage);
  96         }
  97         kfree(paddr);
  98         return ERR_PTR(res);
  99 }
 100
 101 static void ext4_put_link(struct dentry *dentry, struct nameidata *nd,
 102                           void *cookie)
 103 {
 104         struct page *page = cookie;
 105
 106         if (!page) {
 107                 kfree(nd_get_link(nd));
 108         } else {
 109                 kunmap(page);
 110                 page_cache_release(page);
 111         }
 112 }
 113 #endif
 114
 115 static void *ext4_follow_fast_link(struct dentry *dentry, struct nameidata *nd)
 116 {
 117         struct ext4_inode_info *ei = EXT4_I(d_inode(dentry));
 118         nd_set_link(nd, (char *) ei->i_data);
 119         return NULL;
 120 }
 121
 122 const struct inode_operations ext4_symlink_inode_operations = {
 123         .readlink       = generic_readlink,
 124 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 125         .follow_link    = ext4_follow_link,
 126         .put_link       = ext4_put_link,
 127 #else
 128         .follow_link    = page_follow_link_light,
 129         .put_link       = page_put_link,
 130 #endif
 131         .setattr        = ext4_setattr,
 132         .setxattr       = generic_setxattr,
 133         .getxattr       = generic_getxattr,
 134         .listxattr      = ext4_listxattr,
 135         .removexattr    = generic_removexattr,
 136 };
 137
 138 const struct inode_operations ext4_fast_symlink_inode_operations = {
 139         .readlink       = generic_readlink,
 140         .follow_link    = ext4_follow_fast_link,
 141         .setattr        = ext4_setattr,
 142         .setxattr       = generic_setxattr,
 143         .getxattr       = generic_getxattr,
 144         .listxattr      = ext4_listxattr,
 145         .removexattr    = generic_removexattr,
 146 };