fs/ecryptfs/file.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /**
   3  * eCryptfs: Linux filesystem encryption layer
   4  *
   5  * Copyright (C) 1997-2004 Erez Zadok
   6  * Copyright (C) 2001-2004 Stony Brook University
   7  * Copyright (C) 2004-2007 International Business Machines Corp.
   8  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   9  *              Michael C. Thompson <mcthomps@us.ibm.com>
  10  */
  11
  12 #include <linux/file.h>
  13 #include <linux/poll.h>
  14 #include <linux/slab.h>
  15 #include <linux/mount.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/security.h>
  18 #include <linux/compat.h>
  19 #include <linux/fs_stack.h>
  20 #include "ecryptfs_kernel.h"
  21
  22 /**
  23  * ecryptfs_read_update_atime
  24  *
  25  * generic_file_read updates the atime of upper layer inode.  But, it
  26  * doesn't give us a chance to update the atime of the lower layer
  27  * inode.  This function is a wrapper to generic_file_read.  It
  28  * updates the atime of the lower level inode if generic_file_read
  29  * returns without any errors. This is to be used only for file reads.
  30  * The function to be used for directory reads is ecryptfs_read.
  31  */
  32 static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
  33                                 struct iov_iter *to)
  34 {
  35         ssize_t rc;
  36         struct path *path;
  37         struct file *file = iocb->ki_filp;
  38
  39         rc = generic_file_read_iter(iocb, to);
  40         if (rc >= 0) {
  41                 path = ecryptfs_dentry_to_lower_path(file->f_path.dentry);
  42                 touch_atime(path);
  43         }
  44         return rc;
  45 }
  46
  47 struct ecryptfs_getdents_callback {
  48         struct dir_context ctx;
  49         struct dir_context *caller;
  50         struct super_block *sb;
  51         int filldir_called;
  52         int entries_written;
  53 };
  54
  55 /* Inspired by generic filldir in fs/readdir.c */
  56 static int
  57 ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
  58                  int lower_namelen, loff_t offset, u64 ino, unsigned int d_type)
  59 {
  60         struct ecryptfs_getdents_callback *buf =
  61                 container_of(ctx, struct ecryptfs_getdents_callback, ctx);
  62         size_t name_size;
  63         char *name;
  64         int rc;
  65
  66         buf->filldir_called++;
  67         rc = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
  68                                                   buf->sb, lower_name,
  69                                                   lower_namelen);
  70         if (rc) {
  71                 if (rc != -EINVAL) {
  72                         ecryptfs_printk(KERN_DEBUG,
  73                                         "%s: Error attempting to decode and decrypt filename [%s]; rc = [%d]\n",
  74                                         __func__, lower_name, rc);
  75                         return rc;
  76                 }
  77
  78                 /* Mask -EINVAL errors as these are most likely due a plaintext
  79                  * filename present in the lower filesystem despite filename
  80                  * encryption being enabled. One unavoidable example would be
  81                  * the "lost+found" dentry in the root directory of an Ext4
  82                  * filesystem.
  83                  */
  84                 return 0;
  85         }
  86
  87         buf->caller->pos = buf->ctx.pos;
  88         rc = !dir_emit(buf->caller, name, name_size, ino, d_type);
  89         kfree(name);
  90         if (!rc)
  91                 buf->entries_written++;
  92
  93         return rc;
  94 }
  95
  96 /**
  97  * ecryptfs_readdir
  98  * @file: The eCryptfs directory file
  99  * @ctx: The actor to feed the entries to
 100  */
 101 static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
 102 {
 103         int rc;
 104         struct file *lower_file;
 105         struct inode *inode = file_inode(file);
 106         struct ecryptfs_getdents_callback buf = {
 107                 .ctx.actor = ecryptfs_filldir,
 108                 .caller = ctx,
 109                 .sb = inode->i_sb,
 110         };
 111         lower_file = ecryptfs_file_to_lower(file);
 112         rc = iterate_dir(lower_file, &buf.ctx);
 113         ctx->pos = buf.ctx.pos;
 114         if (rc < 0)
 115                 goto out;
 116         if (buf.filldir_called && !buf.entries_written)
 117                 goto out;
 118         if (rc >= 0)
 119                 fsstack_copy_attr_atime(inode,
 120                                         file_inode(lower_file));
 121 out:
 122         return rc;
 123 }
 124
 125 struct kmem_cache *ecryptfs_file_info_cache;
 126
 127 static int read_or_initialize_metadata(struct dentry *dentry)
 128 {
 129         struct inode *inode = d_inode(dentry);
 130         struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
 131         struct ecryptfs_crypt_stat *crypt_stat;
 132         int rc;
 133
 134         crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 135         mount_crypt_stat = &ecryptfs_superblock_to_private(
 136                                                 inode->i_sb)->mount_crypt_stat;
 137         mutex_lock(&crypt_stat->cs_mutex);
 138
 139         if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
 140             crypt_stat->flags & ECRYPTFS_KEY_VALID) {
 141                 rc = 0;
 142                 goto out;
 143         }
 144
 145         rc = ecryptfs_read_metadata(dentry);
 146         if (!rc)
 147                 goto out;
 148
 149         if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
 150                 crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
 151                                        | ECRYPTFS_ENCRYPTED);
 152                 rc = 0;
 153                 goto out;
 154         }
 155
 156         if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
 157             !i_size_read(ecryptfs_inode_to_lower(inode))) {
 158                 rc = ecryptfs_initialize_file(dentry, inode);
 159                 if (!rc)
 160                         goto out;
 161         }
 162
 163         rc = -EIO;
 164 out:
 165         mutex_unlock(&crypt_stat->cs_mutex);
 166         return rc;
 167 }
 168
 169 static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
 170 {
 171         struct file *lower_file = ecryptfs_file_to_lower(file);
 172         /*
 173          * Don't allow mmap on top of file systems that don't support it
 174          * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
 175          * allows recursive mounting, this will need to be extended.
 176          */
 177         if (!lower_file->f_op->mmap)
 178                 return -ENODEV;
 179         return generic_file_mmap(file, vma);
 180 }
 181
 182 /**
 183  * ecryptfs_open
 184  * @inode: inode specifying file to open
 185  * @file: Structure to return filled in
 186  *
 187  * Opens the file specified by inode.
 188  *
 189  * Returns zero on success; non-zero otherwise
 190  */
 191 static int ecryptfs_open(struct inode *inode, struct file *file)
 192 {
 193         int rc = 0;
 194         struct ecryptfs_crypt_stat *crypt_stat = NULL;
 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         /* Released in ecryptfs_release or end of function if failure */
 201         file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
 202         ecryptfs_set_file_private(file, file_info);
 203         if (!file_info) {
 204                 ecryptfs_printk(KERN_ERR,
 205                                 "Error attempting to allocate memory\n");
 206                 rc = -ENOMEM;
 207                 goto out;
 208         }
 209         crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 210         mutex_lock(&crypt_stat->cs_mutex);
 211         if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
 212                 ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
 213                 /* Policy code enabled in future release */
 214                 crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
 215                                       | ECRYPTFS_ENCRYPTED);
 216         }
 217         mutex_unlock(&crypt_stat->cs_mutex);
 218         rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
 219         if (rc) {
 220                 printk(KERN_ERR "%s: Error attempting to initialize "
 221                         "the lower file for the dentry with name "
 222                         "[%pd]; rc = [%d]\n", __func__,
 223                         ecryptfs_dentry, rc);
 224                 goto out_free;
 225         }
 226         if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
 227             == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
 228                 rc = -EPERM;
 229                 printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
 230                        "file must hence be opened RO\n", __func__);
 231                 goto out_put;
 232         }
 233         ecryptfs_set_file_lower(
 234                 file, ecryptfs_inode_to_private(inode)->lower_file);
 235         rc = read_or_initialize_metadata(ecryptfs_dentry);
 236         if (rc)
 237                 goto out_put;
 238         ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
 239                         "[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
 240                         (unsigned long long)i_size_read(inode));
 241         goto out;
 242 out_put:
 243         ecryptfs_put_lower_file(inode);
 244 out_free:
 245         kmem_cache_free(ecryptfs_file_info_cache,
 246                         ecryptfs_file_to_private(file));
 247 out:
 248         return rc;
 249 }
 250
 251 /**
 252  * ecryptfs_dir_open
 253  * @inode: inode specifying file to open
 254  * @file: Structure to return filled in
 255  *
 256  * Opens the file specified by inode.
 257  *
 258  * Returns zero on success; non-zero otherwise
 259  */
 260 static int ecryptfs_dir_open(struct inode *inode, struct file *file)
 261 {
 262         struct dentry *ecryptfs_dentry = file->f_path.dentry;
 263         /* Private value of ecryptfs_dentry allocated in
 264          * ecryptfs_lookup() */
 265         struct ecryptfs_file_info *file_info;
 266         struct file *lower_file;
 267
 268         /* Released in ecryptfs_release or end of function if failure */
 269         file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
 270         ecryptfs_set_file_private(file, file_info);
 271         if (unlikely(!file_info)) {
 272                 ecryptfs_printk(KERN_ERR,
 273                                 "Error attempting to allocate memory\n");
 274                 return -ENOMEM;
 275         }
 276         lower_file = dentry_open(ecryptfs_dentry_to_lower_path(ecryptfs_dentry),
 277                                  file->f_flags, current_cred());
 278         if (IS_ERR(lower_file)) {
 279                 printk(KERN_ERR "%s: Error attempting to initialize "
 280                         "the lower file for the dentry with name "
 281                         "[%pd]; rc = [%ld]\n", __func__,
 282                         ecryptfs_dentry, PTR_ERR(lower_file));
 283                 kmem_cache_free(ecryptfs_file_info_cache, file_info);
 284                 return PTR_ERR(lower_file);
 285         }
 286         ecryptfs_set_file_lower(file, lower_file);
 287         return 0;
 288 }
 289
 290 static int ecryptfs_flush(struct file *file, fl_owner_t td)
 291 {
 292         struct file *lower_file = ecryptfs_file_to_lower(file);
 293
 294         if (lower_file->f_op->flush) {
 295                 filemap_write_and_wait(file->f_mapping);
 296                 return lower_file->f_op->flush(lower_file, td);
 297         }
 298
 299         return 0;
 300 }
 301
 302 static int ecryptfs_release(struct inode *inode, struct file *file)
 303 {
 304         ecryptfs_put_lower_file(inode);
 305         kmem_cache_free(ecryptfs_file_info_cache,
 306                         ecryptfs_file_to_private(file));
 307         return 0;
 308 }
 309
 310 static int ecryptfs_dir_release(struct inode *inode, struct file *file)
 311 {
 312         fput(ecryptfs_file_to_lower(file));
 313         kmem_cache_free(ecryptfs_file_info_cache,
 314                         ecryptfs_file_to_private(file));
 315         return 0;
 316 }
 317
 318 static loff_t ecryptfs_dir_llseek(struct file *file, loff_t offset, int whence)
 319 {
 320         return vfs_llseek(ecryptfs_file_to_lower(file), offset, whence);
 321 }
 322
 323 static int
 324 ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 325 {
 326         int rc;
 327
 328         rc = file_write_and_wait(file);
 329         if (rc)
 330                 return rc;
 331
 332         return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
 333 }
 334
 335 static int ecryptfs_fasync(int fd, struct file *file, int flag)
 336 {
 337         int rc = 0;
 338         struct file *lower_file = NULL;
 339
 340         lower_file = ecryptfs_file_to_lower(file);
 341         if (lower_file->f_op->fasync)
 342                 rc = lower_file->f_op->fasync(fd, lower_file, flag);
 343         return rc;
 344 }
 345
 346 static long
 347 ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 348 {
 349         struct file *lower_file = ecryptfs_file_to_lower(file);
 350         long rc = -ENOTTY;
 351
 352         if (!lower_file->f_op->unlocked_ioctl)
 353                 return rc;
 354
 355         switch (cmd) {
 356         case FITRIM:
 357         case FS_IOC_GETFLAGS:
 358         case FS_IOC_SETFLAGS:
 359         case FS_IOC_GETVERSION:
 360         case FS_IOC_SETVERSION:
 361                 rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
 362                 fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
 363
 364                 return rc;
 365         default:
 366                 return rc;
 367         }
 368 }
 369
 370 #ifdef CONFIG_COMPAT
 371 static long
 372 ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 373 {
 374         struct file *lower_file = ecryptfs_file_to_lower(file);
 375         long rc = -ENOIOCTLCMD;
 376
 377         if (!lower_file->f_op->compat_ioctl)
 378                 return rc;
 379
 380         switch (cmd) {
 381         case FS_IOC32_GETFLAGS:
 382         case FS_IOC32_SETFLAGS:
 383         case FS_IOC32_GETVERSION:
 384         case FS_IOC32_SETVERSION:
 385                 rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
 386                 fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
 387
 388                 return rc;
 389         default:
 390                 return rc;
 391         }
 392 }
 393 #endif
 394
 395 const struct file_operations ecryptfs_dir_fops = {
 396         .iterate_shared = ecryptfs_readdir,
 397         .read = generic_read_dir,
 398         .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 399 #ifdef CONFIG_COMPAT
 400         .compat_ioctl = ecryptfs_compat_ioctl,
 401 #endif
 402         .open = ecryptfs_dir_open,
 403         .release = ecryptfs_dir_release,
 404         .fsync = ecryptfs_fsync,
 405         .llseek = ecryptfs_dir_llseek,
 406 };
 407
 408 const struct file_operations ecryptfs_main_fops = {
 409         .llseek = generic_file_llseek,
 410         .read_iter = ecryptfs_read_update_atime,
 411         .write_iter = generic_file_write_iter,
 412         .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 413 #ifdef CONFIG_COMPAT
 414         .compat_ioctl = ecryptfs_compat_ioctl,
 415 #endif
 416         .mmap = ecryptfs_mmap,
 417         .open = ecryptfs_open,
 418         .flush = ecryptfs_flush,
 419         .release = ecryptfs_release,
 420         .fsync = ecryptfs_fsync,
 421         .fasync = ecryptfs_fasync,
 422         .splice_read = generic_file_splice_read,
 423 };