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         const 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 /*
  48  * ecryptfs_splice_read_update_atime
  49  *
  50  * filemap_splice_read updates the atime of upper layer inode.  But, it
  51  * doesn't give us a chance to update the atime of the lower layer inode.  This
  52  * function is a wrapper to generic_file_read.  It updates the atime of the
  53  * lower level inode if generic_file_read returns without any errors. This is
  54  * to be used only for file reads.  The function to be used for directory reads
  55  * is ecryptfs_read.
  56  */
  57 static ssize_t ecryptfs_splice_read_update_atime(struct file *in, loff_t *ppos,
  58                                                  struct pipe_inode_info *pipe,
  59                                                  size_t len, unsigned int flags)
  60 {
  61         ssize_t rc;
  62         const struct path *path;
  63
  64         rc = filemap_splice_read(in, ppos, pipe, len, flags);
  65         if (rc >= 0) {
  66                 path = ecryptfs_dentry_to_lower_path(in->f_path.dentry);
  67                 touch_atime(path);
  68         }
  69         return rc;
  70 }
  71
  72 struct ecryptfs_getdents_callback {
  73         struct dir_context ctx;
  74         struct dir_context *caller;
  75         struct super_block *sb;
  76         int filldir_called;
  77         int entries_written;
  78 };
  79
  80 /* Inspired by generic filldir in fs/readdir.c */
  81 static bool
  82 ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
  83                  int lower_namelen, loff_t offset, u64 ino, unsigned int d_type)
  84 {
  85         struct ecryptfs_getdents_callback *buf =
  86                 container_of(ctx, struct ecryptfs_getdents_callback, ctx);
  87         size_t name_size;
  88         char *name;
  89         int err;
  90         bool res;
  91
  92         buf->filldir_called++;
  93         err = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
  94                                                    buf->sb, lower_name,
  95                                                    lower_namelen);
  96         if (err) {
  97                 if (err != -EINVAL) {
  98                         ecryptfs_printk(KERN_DEBUG,
  99                                         "%s: Error attempting to decode and decrypt filename [%s]; rc = [%d]\n",
 100                                         __func__, lower_name, err);
 101                         return false;
 102                 }
 103
 104                 /* Mask -EINVAL errors as these are most likely due a plaintext
 105                  * filename present in the lower filesystem despite filename
 106                  * encryption being enabled. One unavoidable example would be
 107                  * the "lost+found" dentry in the root directory of an Ext4
 108                  * filesystem.
 109                  */
 110                 return true;
 111         }
 112
 113         buf->caller->pos = buf->ctx.pos;
 114         res = dir_emit(buf->caller, name, name_size, ino, d_type);
 115         kfree(name);
 116         if (res)
 117                 buf->entries_written++;
 118         return res;
 119 }
 120
 121 /**
 122  * ecryptfs_readdir
 123  * @file: The eCryptfs directory file
 124  * @ctx: The actor to feed the entries to
 125  */
 126 static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
 127 {
 128         int rc;
 129         struct file *lower_file;
 130         struct inode *inode = file_inode(file);
 131         struct ecryptfs_getdents_callback buf = {
 132                 .ctx.actor = ecryptfs_filldir,
 133                 .caller = ctx,
 134                 .sb = inode->i_sb,
 135         };
 136         lower_file = ecryptfs_file_to_lower(file);
 137         rc = iterate_dir(lower_file, &buf.ctx);
 138         ctx->pos = buf.ctx.pos;
 139         if (rc >= 0 && (buf.entries_written || !buf.filldir_called))
 140                 fsstack_copy_attr_atime(inode, file_inode(lower_file));
 141         return rc;
 142 }
 143
 144 struct kmem_cache *ecryptfs_file_info_cache;
 145
 146 static int read_or_initialize_metadata(struct dentry *dentry)
 147 {
 148         struct inode *inode = d_inode(dentry);
 149         struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
 150         struct ecryptfs_crypt_stat *crypt_stat;
 151         int rc;
 152
 153         crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 154         mount_crypt_stat = &ecryptfs_superblock_to_private(
 155                                                 inode->i_sb)->mount_crypt_stat;
 156         mutex_lock(&crypt_stat->cs_mutex);
 157
 158         if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
 159             crypt_stat->flags & ECRYPTFS_KEY_VALID) {
 160                 rc = 0;
 161                 goto out;
 162         }
 163
 164         rc = ecryptfs_read_metadata(dentry);
 165         if (!rc)
 166                 goto out;
 167
 168         if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
 169                 crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
 170                                        | ECRYPTFS_ENCRYPTED);
 171                 rc = 0;
 172                 goto out;
 173         }
 174
 175         if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
 176             !i_size_read(ecryptfs_inode_to_lower(inode))) {
 177                 rc = ecryptfs_initialize_file(dentry, inode);
 178                 if (!rc)
 179                         goto out;
 180         }
 181
 182         rc = -EIO;
 183 out:
 184         mutex_unlock(&crypt_stat->cs_mutex);
 185         return rc;
 186 }
 187
 188 static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
 189 {
 190         struct file *lower_file = ecryptfs_file_to_lower(file);
 191         /*
 192          * Don't allow mmap on top of file systems that don't support it
 193          * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
 194          * allows recursive mounting, this will need to be extended.
 195          */
 196         if (!lower_file->f_op->mmap)
 197                 return -ENODEV;
 198         return generic_file_mmap(file, vma);
 199 }
 200
 201 /**
 202  * ecryptfs_open
 203  * @inode: inode specifying file to open
 204  * @file: Structure to return filled in
 205  *
 206  * Opens the file specified by inode.
 207  *
 208  * Returns zero on success; non-zero otherwise
 209  */
 210 static int ecryptfs_open(struct inode *inode, struct file *file)
 211 {
 212         int rc = 0;
 213         struct ecryptfs_crypt_stat *crypt_stat = NULL;
 214         struct dentry *ecryptfs_dentry = file->f_path.dentry;
 215         /* Private value of ecryptfs_dentry allocated in
 216          * ecryptfs_lookup() */
 217         struct ecryptfs_file_info *file_info;
 218
 219         /* Released in ecryptfs_release or end of function if failure */
 220         file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
 221         ecryptfs_set_file_private(file, file_info);
 222         if (!file_info) {
 223                 ecryptfs_printk(KERN_ERR,
 224                                 "Error attempting to allocate memory\n");
 225                 rc = -ENOMEM;
 226                 goto out;
 227         }
 228         crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
 229         mutex_lock(&crypt_stat->cs_mutex);
 230         if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
 231                 ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
 232                 /* Policy code enabled in future release */
 233                 crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
 234                                       | ECRYPTFS_ENCRYPTED);
 235         }
 236         mutex_unlock(&crypt_stat->cs_mutex);
 237         rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
 238         if (rc) {
 239                 printk(KERN_ERR "%s: Error attempting to initialize "
 240                         "the lower file for the dentry with name "
 241                         "[%pd]; rc = [%d]\n", __func__,
 242                         ecryptfs_dentry, rc);
 243                 goto out_free;
 244         }
 245         if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
 246             == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
 247                 rc = -EPERM;
 248                 printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
 249                        "file must hence be opened RO\n", __func__);
 250                 goto out_put;
 251         }
 252         ecryptfs_set_file_lower(
 253                 file, ecryptfs_inode_to_private(inode)->lower_file);
 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;
 261 out_put:
 262         ecryptfs_put_lower_file(inode);
 263 out_free:
 264         kmem_cache_free(ecryptfs_file_info_cache,
 265                         ecryptfs_file_to_private(file));
 266 out:
 267         return rc;
 268 }
 269
 270 /**
 271  * ecryptfs_dir_open
 272  * @inode: inode specifying file to open
 273  * @file: Structure to return filled in
 274  *
 275  * Opens the file specified by inode.
 276  *
 277  * Returns zero on success; non-zero otherwise
 278  */
 279 static int ecryptfs_dir_open(struct inode *inode, struct file *file)
 280 {
 281         struct dentry *ecryptfs_dentry = file->f_path.dentry;
 282         /* Private value of ecryptfs_dentry allocated in
 283          * ecryptfs_lookup() */
 284         struct ecryptfs_file_info *file_info;
 285         struct file *lower_file;
 286
 287         /* Released in ecryptfs_release or end of function if failure */
 288         file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
 289         ecryptfs_set_file_private(file, file_info);
 290         if (unlikely(!file_info)) {
 291                 ecryptfs_printk(KERN_ERR,
 292                                 "Error attempting to allocate memory\n");
 293                 return -ENOMEM;
 294         }
 295         lower_file = dentry_open(ecryptfs_dentry_to_lower_path(ecryptfs_dentry),
 296                                  file->f_flags, current_cred());
 297         if (IS_ERR(lower_file)) {
 298                 printk(KERN_ERR "%s: Error attempting to initialize "
 299                         "the lower file for the dentry with name "
 300                         "[%pd]; rc = [%ld]\n", __func__,
 301                         ecryptfs_dentry, PTR_ERR(lower_file));
 302                 kmem_cache_free(ecryptfs_file_info_cache, file_info);
 303                 return PTR_ERR(lower_file);
 304         }
 305         ecryptfs_set_file_lower(file, lower_file);
 306         return 0;
 307 }
 308
 309 static int ecryptfs_flush(struct file *file, fl_owner_t td)
 310 {
 311         struct file *lower_file = ecryptfs_file_to_lower(file);
 312
 313         if (lower_file->f_op->flush) {
 314                 filemap_write_and_wait(file->f_mapping);
 315                 return lower_file->f_op->flush(lower_file, td);
 316         }
 317
 318         return 0;
 319 }
 320
 321 static int ecryptfs_release(struct inode *inode, struct file *file)
 322 {
 323         ecryptfs_put_lower_file(inode);
 324         kmem_cache_free(ecryptfs_file_info_cache,
 325                         ecryptfs_file_to_private(file));
 326         return 0;
 327 }
 328
 329 static int ecryptfs_dir_release(struct inode *inode, struct file *file)
 330 {
 331         fput(ecryptfs_file_to_lower(file));
 332         kmem_cache_free(ecryptfs_file_info_cache,
 333                         ecryptfs_file_to_private(file));
 334         return 0;
 335 }
 336
 337 static loff_t ecryptfs_dir_llseek(struct file *file, loff_t offset, int whence)
 338 {
 339         return vfs_llseek(ecryptfs_file_to_lower(file), offset, whence);
 340 }
 341
 342 static int
 343 ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 344 {
 345         int rc;
 346
 347         rc = file_write_and_wait(file);
 348         if (rc)
 349                 return rc;
 350
 351         return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
 352 }
 353
 354 static int ecryptfs_fasync(int fd, struct file *file, int flag)
 355 {
 356         int rc = 0;
 357         struct file *lower_file = NULL;
 358
 359         lower_file = ecryptfs_file_to_lower(file);
 360         if (lower_file->f_op->fasync)
 361                 rc = lower_file->f_op->fasync(fd, lower_file, flag);
 362         return rc;
 363 }
 364
 365 static long
 366 ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 367 {
 368         struct file *lower_file = ecryptfs_file_to_lower(file);
 369         long rc = -ENOTTY;
 370
 371         if (!lower_file->f_op->unlocked_ioctl)
 372                 return rc;
 373
 374         switch (cmd) {
 375         case FITRIM:
 376         case FS_IOC_GETFLAGS:
 377         case FS_IOC_SETFLAGS:
 378         case FS_IOC_GETVERSION:
 379         case FS_IOC_SETVERSION:
 380                 rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
 381                 fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
 382
 383                 return rc;
 384         default:
 385                 return rc;
 386         }
 387 }
 388
 389 #ifdef CONFIG_COMPAT
 390 static long
 391 ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 392 {
 393         struct file *lower_file = ecryptfs_file_to_lower(file);
 394         long rc = -ENOIOCTLCMD;
 395
 396         if (!lower_file->f_op->compat_ioctl)
 397                 return rc;
 398
 399         switch (cmd) {
 400         case FITRIM:
 401         case FS_IOC32_GETFLAGS:
 402         case FS_IOC32_SETFLAGS:
 403         case FS_IOC32_GETVERSION:
 404         case FS_IOC32_SETVERSION:
 405                 rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
 406                 fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
 407
 408                 return rc;
 409         default:
 410                 return rc;
 411         }
 412 }
 413 #endif
 414
 415 const struct file_operations ecryptfs_dir_fops = {
 416         .iterate_shared = ecryptfs_readdir,
 417         .read = generic_read_dir,
 418         .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 419 #ifdef CONFIG_COMPAT
 420         .compat_ioctl = ecryptfs_compat_ioctl,
 421 #endif
 422         .open = ecryptfs_dir_open,
 423         .release = ecryptfs_dir_release,
 424         .fsync = ecryptfs_fsync,
 425         .llseek = ecryptfs_dir_llseek,
 426 };
 427
 428 const struct file_operations ecryptfs_main_fops = {
 429         .llseek = generic_file_llseek,
 430         .read_iter = ecryptfs_read_update_atime,
 431         .write_iter = generic_file_write_iter,
 432         .unlocked_ioctl = ecryptfs_unlocked_ioctl,
 433 #ifdef CONFIG_COMPAT
 434         .compat_ioctl = ecryptfs_compat_ioctl,
 435 #endif
 436         .mmap = ecryptfs_mmap,
 437         .open = ecryptfs_open,
 438         .flush = ecryptfs_flush,
 439         .release = ecryptfs_release,
 440         .fsync = ecryptfs_fsync,
 441         .fasync = ecryptfs_fasync,
 442         .splice_read = ecryptfs_splice_read_update_atime,
 443 };