xref: /openbmc/linux/fs/ecryptfs/file.c (revision 3381df09)
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 FITRIM:
382  	case FS_IOC32_GETFLAGS:
383  	case FS_IOC32_SETFLAGS:
384  	case FS_IOC32_GETVERSION:
385  	case FS_IOC32_SETVERSION:
386  		rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
387  		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
388  
389  		return rc;
390  	default:
391  		return rc;
392  	}
393  }
394  #endif
395  
396  const struct file_operations ecryptfs_dir_fops = {
397  	.iterate_shared = ecryptfs_readdir,
398  	.read = generic_read_dir,
399  	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
400  #ifdef CONFIG_COMPAT
401  	.compat_ioctl = ecryptfs_compat_ioctl,
402  #endif
403  	.open = ecryptfs_dir_open,
404  	.release = ecryptfs_dir_release,
405  	.fsync = ecryptfs_fsync,
406  	.llseek = ecryptfs_dir_llseek,
407  };
408  
409  const struct file_operations ecryptfs_main_fops = {
410  	.llseek = generic_file_llseek,
411  	.read_iter = ecryptfs_read_update_atime,
412  	.write_iter = generic_file_write_iter,
413  	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
414  #ifdef CONFIG_COMPAT
415  	.compat_ioctl = ecryptfs_compat_ioctl,
416  #endif
417  	.mmap = ecryptfs_mmap,
418  	.open = ecryptfs_open,
419  	.flush = ecryptfs_flush,
420  	.release = ecryptfs_release,
421  	.fsync = ecryptfs_fsync,
422  	.fasync = ecryptfs_fasync,
423  	.splice_read = generic_file_splice_read,
424  };
425