mmap.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * eCryptfs: Linux filesystem encryption layer
  4 * This is where eCryptfs coordinates the symmetric encryption and
  5 * decryption of the file data as it passes between the lower
  6 * encrypted file and the upper decrypted file.
  7 *
  8 * Copyright (C) 1997-2003 Erez Zadok
  9 * Copyright (C) 2001-2003 Stony Brook University
 10 * Copyright (C) 2004-2007 International Business Machines Corp.
 11 *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
 12 */
 13
 14#include <linux/pagemap.h>
 15#include <linux/writeback.h>
 16#include <linux/page-flags.h>
 17#include <linux/mount.h>
 18#include <linux/file.h>
 19#include <linux/scatterlist.h>
 20#include <linux/slab.h>
 21#include <linux/xattr.h>
 22#include <linux/unaligned.h>
 23#include "ecryptfs_kernel.h"
 24
 25/*
 26 * This is where we encrypt the data and pass the encrypted data to
 27 * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 28 * entire underlying packets.
 29 */
 30static int ecryptfs_writepages(struct address_space *mapping,
 31		struct writeback_control *wbc)
 32{
 33	struct folio *folio = NULL;
 34	int error;
 35
 36	while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
 37		error = ecryptfs_encrypt_page(folio);
 38		if (error) {
 39			ecryptfs_printk(KERN_WARNING,
 40				"Error encrypting folio (index [0x%.16lx])\n",
 41				folio->index);
 42			folio_clear_uptodate(folio);
 43			mapping_set_error(mapping, error);
 44		}
 45		folio_unlock(folio);
 46	}
 47
 48	return error;
 49}
 50
 51static void strip_xattr_flag(char *page_virt,
 52			     struct ecryptfs_crypt_stat *crypt_stat)
 53{
 54	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 55		size_t written;
 56
 57		crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
 58		ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
 59						&written);
 60		crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
 61	}
 62}
 63
 64/*
 65 *   Header Extent:
 66 *     Octets 0-7:        Unencrypted file size (big-endian)
 67 *     Octets 8-15:       eCryptfs special marker
 68 *     Octets 16-19:      Flags
 69 *      Octet 16:         File format version number (between 0 and 255)
 70 *      Octets 17-18:     Reserved
 71 *      Octet 19:         Bit 1 (lsb): Reserved
 72 *                        Bit 2: Encrypted?
 73 *                        Bits 3-8: Reserved
 74 *     Octets 20-23:      Header extent size (big-endian)
 75 *     Octets 24-25:      Number of header extents at front of file
 76 *                        (big-endian)
 77 *     Octet  26:         Begin RFC 2440 authentication token packet set
 78 */
 79
 80/**
 81 * ecryptfs_copy_up_encrypted_with_header
 82 * @folio: Sort of a ``virtual'' representation of the encrypted lower
 83 *        file. The actual lower file does not have the metadata in
 84 *        the header. This is locked.
 85 * @crypt_stat: The eCryptfs inode's cryptographic context
 86 *
 87 * The ``view'' is the version of the file that userspace winds up
 88 * seeing, with the header information inserted.
 89 */
 90static int
 91ecryptfs_copy_up_encrypted_with_header(struct folio *folio,
 92				       struct ecryptfs_crypt_stat *crypt_stat)
 93{
 94	loff_t extent_num_in_page = 0;
 95	loff_t num_extents_per_page = (PAGE_SIZE
 96				       / crypt_stat->extent_size);
 97	int rc = 0;
 98
 99	while (extent_num_in_page < num_extents_per_page) {
100		loff_t view_extent_num = ((loff_t)folio->index
101					   * num_extents_per_page)
102					  + extent_num_in_page;
103		size_t num_header_extents_at_front =
104			(crypt_stat->metadata_size / crypt_stat->extent_size);
105
106		if (view_extent_num < num_header_extents_at_front) {
107			/* This is a header extent */
108			char *page_virt;
109
110			page_virt = kmap_local_folio(folio, 0);
111			memset(page_virt, 0, PAGE_SIZE);
112			/* TODO: Support more than one header extent */
113			if (view_extent_num == 0) {
114				size_t written;
115
116				rc = ecryptfs_read_xattr_region(
117					page_virt, folio->mapping->host);
118				strip_xattr_flag(page_virt + 16, crypt_stat);
119				ecryptfs_write_header_metadata(page_virt + 20,
120							       crypt_stat,
121							       &written);
122			}
123			kunmap_local(page_virt);
124			flush_dcache_folio(folio);
125			if (rc) {
126				printk(KERN_ERR "%s: Error reading xattr "
127				       "region; rc = [%d]\n", __func__, rc);
128				goto out;
129			}
130		} else {
131			/* This is an encrypted data extent */
132			loff_t lower_offset =
133				((view_extent_num * crypt_stat->extent_size)
134				 - crypt_stat->metadata_size);
135
136			rc = ecryptfs_read_lower_page_segment(
137				folio, (lower_offset >> PAGE_SHIFT),
138				(lower_offset & ~PAGE_MASK),
139				crypt_stat->extent_size, folio->mapping->host);
140			if (rc) {
141				printk(KERN_ERR "%s: Error attempting to read "
142				       "extent at offset [%lld] in the lower "
143				       "file; rc = [%d]\n", __func__,
144				       lower_offset, rc);
145				goto out;
146			}
147		}
148		extent_num_in_page++;
149	}
150out:
151	return rc;
152}
153
154/**
155 * ecryptfs_read_folio
156 * @file: An eCryptfs file
157 * @folio: Folio from eCryptfs inode mapping into which to stick the read data
158 *
159 * Read in a folio, decrypting if necessary.
160 *
161 * Returns zero on success; non-zero on error.
162 */
163static int ecryptfs_read_folio(struct file *file, struct folio *folio)
164{
165	struct inode *inode = folio->mapping->host;
166	struct ecryptfs_crypt_stat *crypt_stat =
167		&ecryptfs_inode_to_private(inode)->crypt_stat;
168	int err = 0;
169
170	if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
171		err = ecryptfs_read_lower_page_segment(folio, folio->index, 0,
172				folio_size(folio), inode);
173	} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
174		if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
175			err = ecryptfs_copy_up_encrypted_with_header(folio,
176					crypt_stat);
177			if (err) {
178				printk(KERN_ERR "%s: Error attempting to copy "
179				       "the encrypted content from the lower "
180				       "file whilst inserting the metadata "
181				       "from the xattr into the header; err = "
182				       "[%d]\n", __func__, err);
183				goto out;
184			}
185
186		} else {
187			err = ecryptfs_read_lower_page_segment(folio,
188					folio->index, 0, folio_size(folio),
189					inode);
190			if (err) {
191				printk(KERN_ERR "Error reading page; err = "
192				       "[%d]\n", err);
193				goto out;
194			}
195		}
196	} else {
197		err = ecryptfs_decrypt_page(folio);
198		if (err) {
199			ecryptfs_printk(KERN_ERR, "Error decrypting page; "
200					"err = [%d]\n", err);
201			goto out;
202		}
203	}
204out:
205	ecryptfs_printk(KERN_DEBUG, "Unlocking folio with index = [0x%.16lx]\n",
206			folio->index);
207	folio_end_read(folio, err == 0);
208	return err;
209}
210
211/*
212 * Called with lower inode mutex held.
213 */
214static int fill_zeros_to_end_of_page(struct folio *folio, unsigned int to)
215{
216	struct inode *inode = folio->mapping->host;
217	int end_byte_in_page;
218
219	if ((i_size_read(inode) / PAGE_SIZE) != folio->index)
220		goto out;
221	end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
222	if (to > end_byte_in_page)
223		end_byte_in_page = to;
224	folio_zero_segment(folio, end_byte_in_page, PAGE_SIZE);
225out:
226	return 0;
227}
228
229/**
230 * ecryptfs_write_begin
231 * @iocb: I/O control block for the eCryptfs file
232 * @mapping: The eCryptfs object
233 * @pos: The file offset at which to start writing
234 * @len: Length of the write
235 * @foliop: Pointer to return the folio
236 * @fsdata: Pointer to return fs data (unused)
237 *
238 * This function must zero any hole we create
239 *
240 * Returns zero on success; non-zero otherwise
241 */
242static int ecryptfs_write_begin(const struct kiocb *iocb,
243			struct address_space *mapping,
244			loff_t pos, unsigned len,
245			struct folio **foliop, void **fsdata)
246{
247	pgoff_t index = pos >> PAGE_SHIFT;
248	struct folio *folio;
249	loff_t prev_page_end_size;
250	int rc = 0;
251
252	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
253			mapping_gfp_mask(mapping));
254	if (IS_ERR(folio))
255		return PTR_ERR(folio);
256	*foliop = folio;
257
258	prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
259	if (!folio_test_uptodate(folio)) {
260		struct ecryptfs_crypt_stat *crypt_stat =
261			&ecryptfs_inode_to_private(mapping->host)->crypt_stat;
262
263		if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
264			rc = ecryptfs_read_lower_page_segment(
265				folio, index, 0, PAGE_SIZE, mapping->host);
266			if (rc) {
267				printk(KERN_ERR "%s: Error attempting to read "
268				       "lower page segment; rc = [%d]\n",
269				       __func__, rc);
270				folio_clear_uptodate(folio);
271				goto out;
272			} else
273				folio_mark_uptodate(folio);
274		} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
275			if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
276				rc = ecryptfs_copy_up_encrypted_with_header(
277					folio, crypt_stat);
278				if (rc) {
279					printk(KERN_ERR "%s: Error attempting "
280					       "to copy the encrypted content "
281					       "from the lower file whilst "
282					       "inserting the metadata from "
283					       "the xattr into the header; rc "
284					       "= [%d]\n", __func__, rc);
285					folio_clear_uptodate(folio);
286					goto out;
287				}
288				folio_mark_uptodate(folio);
289			} else {
290				rc = ecryptfs_read_lower_page_segment(
291					folio, index, 0, PAGE_SIZE,
292					mapping->host);
293				if (rc) {
294					printk(KERN_ERR "%s: Error reading "
295					       "page; rc = [%d]\n",
296					       __func__, rc);
297					folio_clear_uptodate(folio);
298					goto out;
299				}
300				folio_mark_uptodate(folio);
301			}
302		} else {
303			if (prev_page_end_size
304			    >= i_size_read(mapping->host)) {
305				folio_zero_range(folio, 0, PAGE_SIZE);
306				folio_mark_uptodate(folio);
307			} else if (len < PAGE_SIZE) {
308				rc = ecryptfs_decrypt_page(folio);
309				if (rc) {
310					printk(KERN_ERR "%s: Error decrypting "
311					       "page at index [%ld]; "
312					       "rc = [%d]\n",
313					       __func__, folio->index, rc);
314					folio_clear_uptodate(folio);
315					goto out;
316				}
317				folio_mark_uptodate(folio);
318			}
319		}
320	}
321	/* If creating a page or more of holes, zero them out via truncate.
322	 * Note, this will increase i_size. */
323	if (index != 0) {
324		if (prev_page_end_size > i_size_read(mapping->host)) {
325			rc = ecryptfs_truncate(iocb->ki_filp->f_path.dentry,
326					       prev_page_end_size);
327			if (rc) {
328				printk(KERN_ERR "%s: Error on attempt to "
329				       "truncate to (higher) offset [%lld];"
330				       " rc = [%d]\n", __func__,
331				       prev_page_end_size, rc);
332				goto out;
333			}
334		}
335	}
336	/* Writing to a new page, and creating a small hole from start
337	 * of page?  Zero it out. */
338	if ((i_size_read(mapping->host) == prev_page_end_size)
339	    && (pos != 0))
340		folio_zero_range(folio, 0, PAGE_SIZE);
341out:
342	if (unlikely(rc)) {
343		folio_unlock(folio);
344		folio_put(folio);
345	}
346	return rc;
347}
348
349/*
350 * ecryptfs_write_inode_size_to_header
351 *
352 * Writes the lower file size to the first 8 bytes of the header.
353 *
354 * Returns zero on success; non-zero on error.
355 */
356static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
357{
358	char *file_size_virt;
359	int rc;
360
361	file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
362	if (!file_size_virt) {
363		rc = -ENOMEM;
364		goto out;
365	}
366	put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
367	rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
368				  sizeof(u64));
369	kfree(file_size_virt);
370	if (rc < 0)
371		printk(KERN_ERR "%s: Error writing file size to header; "
372		       "rc = [%d]\n", __func__, rc);
373	else
374		rc = 0;
375out:
376	return rc;
377}
378
379struct kmem_cache *ecryptfs_xattr_cache;
380
381static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
382{
383	ssize_t size;
384	void *xattr_virt;
385	struct dentry *lower_dentry =
386		ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
387	struct inode *lower_inode = d_inode(lower_dentry);
388	int rc;
389
390	if (!(lower_inode->i_opflags & IOP_XATTR)) {
391		printk(KERN_WARNING
392		       "No support for setting xattr in lower filesystem\n");
393		rc = -ENOSYS;
394		goto out;
395	}
396	xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
397	if (!xattr_virt) {
398		rc = -ENOMEM;
399		goto out;
400	}
401	inode_lock(lower_inode);
402	size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
403			      xattr_virt, PAGE_SIZE);
404	if (size < 0)
405		size = 8;
406	put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
407	rc = __vfs_setxattr(&nop_mnt_idmap, lower_dentry, lower_inode,
408			    ECRYPTFS_XATTR_NAME, xattr_virt, size, 0);
409	inode_unlock(lower_inode);
410	if (rc)
411		printk(KERN_ERR "Error whilst attempting to write inode size "
412		       "to lower file xattr; rc = [%d]\n", rc);
413	kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
414out:
415	return rc;
416}
417
418int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
419{
420	struct ecryptfs_crypt_stat *crypt_stat;
421
422	crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
423	BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
424	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
425		return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
426	else
427		return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
428}
429
430/**
431 * ecryptfs_write_end
432 * @iocb: I/O control block for the eCryptfs file
433 * @mapping: The eCryptfs object
434 * @pos: The file position
435 * @len: The length of the data (unused)
436 * @copied: The amount of data copied
437 * @folio: The eCryptfs folio
438 * @fsdata: The fsdata (unused)
439 */
440static int ecryptfs_write_end(const struct kiocb *iocb,
441			struct address_space *mapping,
442			loff_t pos, unsigned len, unsigned copied,
443			struct folio *folio, void *fsdata)
444{
445	pgoff_t index = pos >> PAGE_SHIFT;
446	unsigned from = pos & (PAGE_SIZE - 1);
447	unsigned to = from + copied;
448	struct inode *ecryptfs_inode = mapping->host;
449	struct ecryptfs_crypt_stat *crypt_stat =
450		&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
451	int rc;
452
453	ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
454			"(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
455	if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
456		rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
457				folio, 0, to);
458		if (!rc) {
459			rc = copied;
460			fsstack_copy_inode_size(ecryptfs_inode,
461				ecryptfs_inode_to_lower(ecryptfs_inode));
462		}
463		goto out;
464	}
465	if (!folio_test_uptodate(folio)) {
466		if (copied < PAGE_SIZE) {
467			rc = 0;
468			goto out;
469		}
470		folio_mark_uptodate(folio);
471	}
472	/* Fills in zeros if 'to' goes beyond inode size */
473	rc = fill_zeros_to_end_of_page(folio, to);
474	if (rc) {
475		ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
476			"zeros in page with index = [0x%.16lx]\n", index);
477		goto out;
478	}
479	rc = ecryptfs_encrypt_page(folio);
480	if (rc) {
481		ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
482				"index [0x%.16lx])\n", index);
483		goto out;
484	}
485	if (pos + copied > i_size_read(ecryptfs_inode)) {
486		i_size_write(ecryptfs_inode, pos + copied);
487		ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
488			"[0x%.16llx]\n",
489			(unsigned long long)i_size_read(ecryptfs_inode));
490	}
491	rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
492	if (rc)
493		printk(KERN_ERR "Error writing inode size to metadata; "
494		       "rc = [%d]\n", rc);
495	else
496		rc = copied;
497out:
498	folio_unlock(folio);
499	folio_put(folio);
500	return rc;
501}
502
503static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
504{
505	struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
506	int ret = bmap(lower_inode, &block);
507
508	if (ret)
509		return 0;
510	return block;
511}
512
513#include <linux/buffer_head.h>
514
515const struct address_space_operations ecryptfs_aops = {
516	/*
517	 * XXX: This is pretty broken for multiple reasons: ecryptfs does not
518	 * actually use buffer_heads, and ecryptfs will crash without
519	 * CONFIG_BLOCK.  But it matches the behavior before the default for
520	 * address_space_operations without the ->dirty_folio method was
521	 * cleaned up, so this is the best we can do without maintainer
522	 * feedback.
523	 */
524#ifdef CONFIG_BLOCK
525	.dirty_folio	= block_dirty_folio,
526	.invalidate_folio = block_invalidate_folio,
527#endif
528	.writepages = ecryptfs_writepages,
529	.read_folio = ecryptfs_read_folio,
530	.write_begin = ecryptfs_write_begin,
531	.write_end = ecryptfs_write_end,
532	.migrate_folio = filemap_migrate_folio,
533	.bmap = ecryptfs_bmap,
534};