fs/ecryptfs/file.c

   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  */
  47 static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
  48                                 struct iov_iter *to)
  49 {
  50         ssize_t rc;
  51         struct path *path;
  52         struct file *file = iocb->ki_filp;
  53
  54         rc = generic_file_read_iter(iocb, to);
  55         /*
  56          * Even though this is a async interface, we need to wait
  57          * for IO to finish to update atime
  58          */
  59         if (-EIOCBQUEUED == rc)
  60                 rc = wait_on_sync_kiocb(iocb);
  61         if (rc >= 0) {
  62                 path = ecryptfs_dentry_to_lower_path(file->f_path.dentry);
  63                 touch_atime(path);
  64         }
  65         return rc;
  66 }
  67
  68 struct ecryptfs_getdents_callback {
  69         struct dir_context ctx;
  70         struct dir_context *caller;
  71         struct super_block *sb;
  72         int filldir_called;
  73         int entries_written;
  74 };
  75
  76 /* Inspired by generic filldir in fs/readdir.c */
  77 static int
  78 ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
  79                  int lower_namelen, loff_t offset, u64 ino, unsigned int d_type)
  80 {
  81         struct ecryptfs_getdents_callback *buf =
  82                 container_of(ctx, struct ecryptfs_getdents_callback, ctx);
  83         size_t name_size;
  84         char *name;
  85         int rc;
  86
  87         buf->filldir_called++;
  88         rc = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
  89                                                   buf->sb, lower_name,
  90                                                   lower_namelen);
  91         if (rc) {
  92                 printk(KERN_ERR "%s: Error attempting to decode and decrypt "
  93                        "filename [%s]; rc = [%d]\n", __func__, lower_name,
  94                        rc);
  95                 goto out;
  96         }
  97         buf->caller->pos = buf->ctx.pos;
  98         rc = !dir_emit(buf->caller, name, name_size, ino, d_type);
  99         kfree(name);
 100         if (!rc)
 101                 buf->entries_written++;
 102 out:
 103         return rc;
 104 }
 105
 106 /**
 107  * ecryptfs_readdir
 108  * @file: The eCryptfs directory file
 109  * @ctx: The actor to feed the entries to
 110  */
 111 static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
 112 {
 113         int rc;
 114         struct file *lower_file;
 115         struct inode *inode = file_inode(file);
 116         struct ecryptfs_getdents_callback buf = {
 117                 .ctx.actor = ecryptfs_filldir,
 118                 .caller = ctx,
 119                 .sb = inode->i_sb,
 120         };
 121         lower_file = ecryptfs_file_to_lower(file);
 122         lower_file->f_pos = ctx->pos;
 123         rc = iterate_dir(lower_file, &buf.ctx);
 124         ctx->pos = buf.ctx.pos;
 125         if (rc < 0)
 126                 goto out;
 127         if (buf.filldir_called && !buf.entries_written)
 128                 goto out;
 129         if (rc >= 0)
 130                 fsstack_copy_attr_atime(inode,
 131                                         file_inode(lower_file));
 132 out:
 133         return rc;
 134 }
 135
 136 struct kmem_cache *ecryptfs_file_info_cache;
 137
 138 static int read_or_initialize_metadata(struct dentry *dentry)
 139 {
 140         struct inode *inode = dentry->d_inode;
 141         struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
 142         struct ecryptfs_crypt_stat *crypt_stat;
 143         int rc;
 144
 145         crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 146         mount_crypt_stat = &ecryptfs_superblock_to_private(
 147                                                 inode->i_sb)->mount_crypt_stat;
 148         mutex_lock(&crypt_stat->cs_mutex);
 149
 150         if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
 151             crypt_stat->flags & ECRYPTFS_KEY_VALID) {
 152                 rc = 0;
 153                 goto out;
 154         }
 155
 156         rc = ecryptfs_read_metadata(dentry);
 157         if (!rc)
 158                 goto out;
 159
 160         if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
 161                 crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
 162                                        | ECRYPTFS_ENCRYPTED);
 163                 rc = 0;
 164                 goto out;
 165         }
 166
 167         if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
 168             !i_size_read(ecryptfs_inode_to_lower(inode))) {
 169                 rc = ecryptfs_initialize_file(dentry, inode);
 170                 if (!rc)
 171                         goto out;
 172         }
 173
 174         rc = -EIO;
 175 out:
 176         mutex_unlock(&crypt_stat->cs_mutex);
 177         return rc;
 178 }
 179
 180 /**
 181  * ecryptfs_open
 182  * @inode: inode speciying file to open
 183  * @file: Structure to return filled in
 184  *
 185  * Opens the file specified by inode.
 186  *
 187  * Returns zero on success; non-zero otherwise
 188  */
 189 static int ecryptfs_open(struct inode *inode, struct file *file)
 190 {
 191         int rc = 0;
 192         struct ecryptfs_crypt_stat *crypt_stat = NULL;
 193         struct dentry *ecryptfs_dentry = file->f_path.dentry;
 194         /* Private value of ecryptfs_dentry allocated in
 195          * ecryptfs_lookup() */
 196         struct ecryptfs_file_info *file_info;
 197
 198         /* Released in ecryptfs_release or end of function if failure */
 199         file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
 200         ecryptfs_set_file_private(file, file_info);
 201         if (!file_info) {
 202                 ecryptfs_printk(KERN_ERR,
 203                                 "Error attempting to allocate memory\n");
 204                 rc = -ENOMEM;
 205                 goto out;
 206         }
 207         crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 208         mutex_lock(&crypt_stat->cs_mutex);
 209         if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
 210                 ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
 211                 /* Policy code enabled in future release */
 212                 crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
 213                                       | ECRYPTFS_ENCRYPTED);
 214         }
 215         mutex_unlock(&crypt_stat->cs_mutex);
 216         rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
 217         if (rc) {
 218                 printk(KERN_ERR "%s: Error attempting to initialize "
 219                         "the lower file for the dentry with name "
 220                         "[%pd]; rc = [%d]\n", __func__,
 221                         ecryptfs_dentry, rc);
 222                 goto out_free;
 223         }
 224         if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
 225             == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
 226                 rc = -EPERM;
 227                 printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
 228                        "file must hence be opened RO\n", __func__);
 229                 goto out_put;
 230         }
 231         ecryptfs_set_file_lower(
 232                 file, ecryptfs_inode_to_private(inode)->lower_file);
 233         if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {
 234                 ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
 235                 mutex_lock(&crypt_stat->cs_mutex);
 236                 crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
 237                 mutex_unlock(&crypt_stat->cs_mutex);
 238                 rc = 0;
 239                 goto out;
 240         }
 241         rc = read_or_initialize_metadata(ecryptfs_dentry);
 242         if (rc)
 243                 goto out_put;
 244         ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
 245                         "[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
 246                         (unsigned long long)i_size_read(inode));
 247         goto out;
 248 out_put:
 249         ecryptfs_put_lower_file(inode);
 250 out_free:
 251         kmem_cache_free(ecryptfs_file_info_cache,
 252                         ecryptfs_file_to_private(file));
 253 out:
 254         return rc;
 255 }
 256
 257 static int ecryptfs_flush(struct file *file, fl_owner_t td)
 258 {
 259         struct file *lower_file = ecryptfs_file_to_lower(file);
 260
 261         if (lower_file->f_op->flush) {
 262                 filemap_write_and_wait(file->f_mapping);
 263                 return lower_file->f_op->flush(lower_file, td);
 264         }
 265
 266         return 0;
 267 }
 268
 269 static int ecryptfs_release(struct inode *inode, struct file *file)
 270 {
 271         ecryptfs_put_lower_file(inode);
 272         kmem_cache_free(ecryptfs_file_info_cache,
 273                         ecryptfs_file_to_private(file));
 274         return 0;
 275 }
 276
 277 static int
 278 ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 279 {
 280         int rc;
 281
 282         rc = filemap_write_and_wait(file->f_mapping);
 283         if (rc)
 284                 return rc;
 285
 286         return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
 287 }
 288
 289 static int ecryptfs_fasync(int fd, struct file *file, int flag)
 290 {
 291         int rc = 0;
 292         struct file *lower_file = NULL;
 293
 294         lower_file = ecryptfs_file_to_lower(file);
 295         if (lower_file->f_op->fasync)
 296                 rc = lower_file->f_op->fasync(fd, lower_file, flag);
 297         return rc;
 298 }
 299
 300 static long
 301 ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 302 {
 303         struct file *lower_file = ecryptfs_file_to_lower(file);
 304         long rc = -ENOTTY;
 305
 306         if (lower_file->f_op->unlocked_ioctl)
 307                 rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
 308         return rc;
 309 }
 310
 311 #ifdef CONFIG_COMPAT
 312 static long
 313 ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 314 {
 315         struct file *lower_file = ecryptfs_file_to_lower(file);
 316         long rc = -ENOIOCTLCMD;
 317
 318         if (lower_file->f_op->compat_ioctl)
 319                 rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
 320         return rc;
 321 }
 322 #endif
 323
 324 const struct file_operations ecryptfs_dir_fops = {
 325         .iterate = ecryptfs_readdir,
 326         .read = generic_read_dir,
 327         .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 328 #ifdef CONFIG_COMPAT
 329         .compat_ioctl = ecryptfs_compat_ioctl,
 330 #endif
 331         .open = ecryptfs_open,
 332         .flush = ecryptfs_flush,
 333         .release = ecryptfs_release,
 334         .fsync = ecryptfs_fsync,
 335         .fasync = ecryptfs_fasync,
 336         .splice_read = generic_file_splice_read,
 337         .llseek = default_llseek,
 338 };
 339
 340 const struct file_operations ecryptfs_main_fops = {
 341         .llseek = generic_file_llseek,
 342         .read = new_sync_read,
 343         .read_iter = ecryptfs_read_update_atime,
 344         .write = new_sync_write,
 345         .write_iter = generic_file_write_iter,
 346         .iterate = ecryptfs_readdir,
 347         .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 348 #ifdef CONFIG_COMPAT
 349         .compat_ioctl = ecryptfs_compat_ioctl,
 350 #endif
 351         .mmap = generic_file_mmap,
 352         .open = ecryptfs_open,
 353         .flush = ecryptfs_flush,
 354         .release = ecryptfs_release,
 355         .fsync = ecryptfs_fsync,
 356         .fasync = ecryptfs_fasync,
 357         .splice_read = generic_file_splice_read,
 358 };