linux/fs/ecryptfs/file.c
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   1/**
   2 * eCryptfs: Linux filesystem encryption layer
   3 *
   4 * Copyright (C) 1997-2004 Erez Zadok
   5 * Copyright (C) 2001-2004 Stony Brook University
   6 * Copyright (C) 2004-2007 International Business Machines Corp.
   7 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   8 *              Michael C. Thompson <mcthomps@us.ibm.com>
   9 *
  10 * This program is free software; you can redistribute it and/or
  11 * modify it under the terms of the GNU General Public License as
  12 * published by the Free Software Foundation; either version 2 of the
  13 * License, or (at your option) any later version.
  14 *
  15 * This program is distributed in the hope that it will be useful, but
  16 * WITHOUT ANY WARRANTY; without even the implied warranty of
  17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18 * General Public License for more details.
  19 *
  20 * You should have received a copy of the GNU General Public License
  21 * along with this program; if not, write to the Free Software
  22 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  23 * 02111-1307, USA.
  24 */
  25
  26#include <linux/file.h>
  27#include <linux/poll.h>
  28#include <linux/slab.h>
  29#include <linux/mount.h>
  30#include <linux/pagemap.h>
  31#include <linux/security.h>
  32#include <linux/compat.h>
  33#include <linux/fs_stack.h>
  34#include <linux/aio.h>
  35#include "ecryptfs_kernel.h"
  36
  37/**
  38 * ecryptfs_read_update_atime
  39 *
  40 * generic_file_read updates the atime of upper layer inode.  But, it
  41 * doesn't give us a chance to update the atime of the lower layer
  42 * inode.  This function is a wrapper to generic_file_read.  It
  43 * updates the atime of the lower level inode if generic_file_read
  44 * returns without any errors. This is to be used only for file reads.
  45 * The function to be used for directory reads is ecryptfs_read.
  46 */
  47static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
  48                                const struct iovec *iov,
  49                                unsigned long nr_segs, loff_t pos)
  50{
  51        ssize_t rc;
  52        struct path *path;
  53        struct file *file = iocb->ki_filp;
  54
  55        rc = generic_file_aio_read(iocb, iov, nr_segs, pos);
  56        /*
  57         * Even though this is a async interface, we need to wait
  58         * for IO to finish to update atime
  59         */
  60        if (-EIOCBQUEUED == rc)
  61                rc = wait_on_sync_kiocb(iocb);
  62        if (rc >= 0) {
  63                path = ecryptfs_dentry_to_lower_path(file->f_path.dentry);
  64                touch_atime(path);
  65        }
  66        return rc;
  67}
  68
  69struct ecryptfs_getdents_callback {
  70        struct dir_context ctx;
  71        struct dir_context *caller;
  72        struct super_block *sb;
  73        int filldir_called;
  74        int entries_written;
  75};
  76
  77/* Inspired by generic filldir in fs/readdir.c */
  78static int
  79ecryptfs_filldir(void *dirent, const char *lower_name, int lower_namelen,
  80                 loff_t offset, u64 ino, unsigned int d_type)
  81{
  82        struct ecryptfs_getdents_callback *buf =
  83            (struct ecryptfs_getdents_callback *)dirent;
  84        size_t name_size;
  85        char *name;
  86        int rc;
  87
  88        buf->filldir_called++;
  89        rc = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
  90                                                  buf->sb, lower_name,
  91                                                  lower_namelen);
  92        if (rc) {
  93                printk(KERN_ERR "%s: Error attempting to decode and decrypt "
  94                       "filename [%s]; rc = [%d]\n", __func__, lower_name,
  95                       rc);
  96                goto out;
  97        }
  98        buf->caller->pos = buf->ctx.pos;
  99        rc = !dir_emit(buf->caller, name, name_size, ino, d_type);
 100        kfree(name);
 101        if (!rc)
 102                buf->entries_written++;
 103out:
 104        return rc;
 105}
 106
 107/**
 108 * ecryptfs_readdir
 109 * @file: The eCryptfs directory file
 110 * @ctx: The actor to feed the entries to
 111 */
 112static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
 113{
 114        int rc;
 115        struct file *lower_file;
 116        struct inode *inode = file_inode(file);
 117        struct ecryptfs_getdents_callback buf = {
 118                .ctx.actor = ecryptfs_filldir,
 119                .caller = ctx,
 120                .sb = inode->i_sb,
 121        };
 122        lower_file = ecryptfs_file_to_lower(file);
 123        lower_file->f_pos = ctx->pos;
 124        rc = iterate_dir(lower_file, &buf.ctx);
 125        ctx->pos = buf.ctx.pos;
 126        if (rc < 0)
 127                goto out;
 128        if (buf.filldir_called && !buf.entries_written)
 129                goto out;
 130        if (rc >= 0)
 131                fsstack_copy_attr_atime(inode,
 132                                        file_inode(lower_file));
 133out:
 134        return rc;
 135}
 136
 137struct kmem_cache *ecryptfs_file_info_cache;
 138
 139static int read_or_initialize_metadata(struct dentry *dentry)
 140{
 141        struct inode *inode = dentry->d_inode;
 142        struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
 143        struct ecryptfs_crypt_stat *crypt_stat;
 144        int rc;
 145
 146        crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 147        mount_crypt_stat = &ecryptfs_superblock_to_private(
 148                                                inode->i_sb)->mount_crypt_stat;
 149        mutex_lock(&crypt_stat->cs_mutex);
 150
 151        if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
 152            crypt_stat->flags & ECRYPTFS_KEY_VALID) {
 153                rc = 0;
 154                goto out;
 155        }
 156
 157        rc = ecryptfs_read_metadata(dentry);
 158        if (!rc)
 159                goto out;
 160
 161        if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
 162                crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
 163                                       | ECRYPTFS_ENCRYPTED);
 164                rc = 0;
 165                goto out;
 166        }
 167
 168        if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
 169            !i_size_read(ecryptfs_inode_to_lower(inode))) {
 170                rc = ecryptfs_initialize_file(dentry, inode);
 171                if (!rc)
 172                        goto out;
 173        }
 174
 175        rc = -EIO;
 176out:
 177        mutex_unlock(&crypt_stat->cs_mutex);
 178        return rc;
 179}
 180
 181/**
 182 * ecryptfs_open
 183 * @inode: inode speciying file to open
 184 * @file: Structure to return filled in
 185 *
 186 * Opens the file specified by inode.
 187 *
 188 * Returns zero on success; non-zero otherwise
 189 */
 190static int ecryptfs_open(struct inode *inode, struct file *file)
 191{
 192        int rc = 0;
 193        struct ecryptfs_crypt_stat *crypt_stat = NULL;
 194        struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
 195        struct dentry *ecryptfs_dentry = file->f_path.dentry;
 196        /* Private value of ecryptfs_dentry allocated in
 197         * ecryptfs_lookup() */
 198        struct ecryptfs_file_info *file_info;
 199
 200        mount_crypt_stat = &ecryptfs_superblock_to_private(
 201                ecryptfs_dentry->d_sb)->mount_crypt_stat;
 202        if ((mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
 203            && ((file->f_flags & O_WRONLY) || (file->f_flags & O_RDWR)
 204                || (file->f_flags & O_CREAT) || (file->f_flags & O_TRUNC)
 205                || (file->f_flags & O_APPEND))) {
 206                printk(KERN_WARNING "Mount has encrypted view enabled; "
 207                       "files may only be read\n");
 208                rc = -EPERM;
 209                goto out;
 210        }
 211        /* Released in ecryptfs_release or end of function if failure */
 212        file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
 213        ecryptfs_set_file_private(file, file_info);
 214        if (!file_info) {
 215                ecryptfs_printk(KERN_ERR,
 216                                "Error attempting to allocate memory\n");
 217                rc = -ENOMEM;
 218                goto out;
 219        }
 220        crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 221        mutex_lock(&crypt_stat->cs_mutex);
 222        if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
 223                ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
 224                /* Policy code enabled in future release */
 225                crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
 226                                      | ECRYPTFS_ENCRYPTED);
 227        }
 228        mutex_unlock(&crypt_stat->cs_mutex);
 229        rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
 230        if (rc) {
 231                printk(KERN_ERR "%s: Error attempting to initialize "
 232                        "the lower file for the dentry with name "
 233                        "[%s]; rc = [%d]\n", __func__,
 234                        ecryptfs_dentry->d_name.name, rc);
 235                goto out_free;
 236        }
 237        if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
 238            == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
 239                rc = -EPERM;
 240                printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
 241                       "file must hence be opened RO\n", __func__);
 242                goto out_put;
 243        }
 244        ecryptfs_set_file_lower(
 245                file, ecryptfs_inode_to_private(inode)->lower_file);
 246        if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {
 247                ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
 248                mutex_lock(&crypt_stat->cs_mutex);
 249                crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
 250                mutex_unlock(&crypt_stat->cs_mutex);
 251                rc = 0;
 252                goto out;
 253        }
 254        rc = read_or_initialize_metadata(ecryptfs_dentry);
 255        if (rc)
 256                goto out_put;
 257        ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
 258                        "[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
 259                        (unsigned long long)i_size_read(inode));
 260        goto out;
 261out_put:
 262        ecryptfs_put_lower_file(inode);
 263out_free:
 264        kmem_cache_free(ecryptfs_file_info_cache,
 265                        ecryptfs_file_to_private(file));
 266out:
 267        return rc;
 268}
 269
 270static int ecryptfs_flush(struct file *file, fl_owner_t td)
 271{
 272        struct file *lower_file = ecryptfs_file_to_lower(file);
 273
 274        if (lower_file->f_op && lower_file->f_op->flush) {
 275                filemap_write_and_wait(file->f_mapping);
 276                return lower_file->f_op->flush(lower_file, td);
 277        }
 278
 279        return 0;
 280}
 281
 282static int ecryptfs_release(struct inode *inode, struct file *file)
 283{
 284        ecryptfs_put_lower_file(inode);
 285        kmem_cache_free(ecryptfs_file_info_cache,
 286                        ecryptfs_file_to_private(file));
 287        return 0;
 288}
 289
 290static int
 291ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 292{
 293        int rc;
 294
 295        rc = filemap_write_and_wait(file->f_mapping);
 296        if (rc)
 297                return rc;
 298
 299        return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
 300}
 301
 302static int ecryptfs_fasync(int fd, struct file *file, int flag)
 303{
 304        int rc = 0;
 305        struct file *lower_file = NULL;
 306
 307        lower_file = ecryptfs_file_to_lower(file);
 308        if (lower_file->f_op && lower_file->f_op->fasync)
 309                rc = lower_file->f_op->fasync(fd, lower_file, flag);
 310        return rc;
 311}
 312
 313static long
 314ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 315{
 316        struct file *lower_file = NULL;
 317        long rc = -ENOTTY;
 318
 319        if (ecryptfs_file_to_private(file))
 320                lower_file = ecryptfs_file_to_lower(file);
 321        if (lower_file && lower_file->f_op && lower_file->f_op->unlocked_ioctl)
 322                rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
 323        return rc;
 324}
 325
 326#ifdef CONFIG_COMPAT
 327static long
 328ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 329{
 330        struct file *lower_file = NULL;
 331        long rc = -ENOIOCTLCMD;
 332
 333        if (ecryptfs_file_to_private(file))
 334                lower_file = ecryptfs_file_to_lower(file);
 335        if (lower_file && lower_file->f_op && lower_file->f_op->compat_ioctl)
 336                rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
 337        return rc;
 338}
 339#endif
 340
 341const struct file_operations ecryptfs_dir_fops = {
 342        .iterate = ecryptfs_readdir,
 343        .read = generic_read_dir,
 344        .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 345#ifdef CONFIG_COMPAT
 346        .compat_ioctl = ecryptfs_compat_ioctl,
 347#endif
 348        .open = ecryptfs_open,
 349        .flush = ecryptfs_flush,
 350        .release = ecryptfs_release,
 351        .fsync = ecryptfs_fsync,
 352        .fasync = ecryptfs_fasync,
 353        .splice_read = generic_file_splice_read,
 354        .llseek = default_llseek,
 355};
 356
 357const struct file_operations ecryptfs_main_fops = {
 358        .llseek = generic_file_llseek,
 359        .read = do_sync_read,
 360        .aio_read = ecryptfs_read_update_atime,
 361        .write = do_sync_write,
 362        .aio_write = generic_file_aio_write,
 363        .iterate = ecryptfs_readdir,
 364        .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 365#ifdef CONFIG_COMPAT
 366        .compat_ioctl = ecryptfs_compat_ioctl,
 367#endif
 368        .mmap = generic_file_mmap,
 369        .open = ecryptfs_open,
 370        .flush = ecryptfs_flush,
 371        .release = ecryptfs_release,
 372        .fsync = ecryptfs_fsync,
 373        .fasync = ecryptfs_fasync,
 374        .splice_read = generic_file_splice_read,
 375};
 376
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