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 */
 32static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
 33				struct iov_iter *to)
 34{
 35	ssize_t rc;
 36	struct file *file = iocb->ki_filp;
 37
 38	rc = generic_file_read_iter(iocb, to);
 39	if (rc >= 0) {
 40		struct path path = ecryptfs_lower_path(file->f_path.dentry);
 41		touch_atime(&path);
 42	}
 43	return rc;
 44}
 45
 46/*
 47 * ecryptfs_splice_read_update_atime
 48 *
 49 * filemap_splice_read updates the atime of upper layer inode.  But, it
 50 * doesn't give us a chance to update the atime of the lower layer inode.  This
 51 * function is a wrapper to generic_file_read.  It updates the atime of the
 52 * lower level inode if generic_file_read returns without any errors. This is
 53 * to be used only for file reads.  The function to be used for directory reads
 54 * is ecryptfs_read.
 55 */
 56static ssize_t ecryptfs_splice_read_update_atime(struct file *in, loff_t *ppos,
 57						 struct pipe_inode_info *pipe,
 58						 size_t len, unsigned int flags)
 59{
 60	ssize_t rc;
 61
 62	rc = filemap_splice_read(in, ppos, pipe, len, flags);
 63	if (rc >= 0) {
 64		struct path path = ecryptfs_lower_path(in->f_path.dentry);
 65		touch_atime(&path);
 66	}
 67	return rc;
 68}
 69
 70struct ecryptfs_getdents_callback {
 71	struct dir_context ctx;
 72	struct dir_context *caller;
 73	struct super_block *sb;
 74	int filldir_called;
 75	int entries_written;
 76};
 77
 78/* Inspired by generic filldir in fs/readdir.c */
 79static bool
 80ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
 81		 int lower_namelen, loff_t offset, u64 ino, unsigned int d_type)
 82{
 83	struct ecryptfs_getdents_callback *buf =
 84		container_of(ctx, struct ecryptfs_getdents_callback, ctx);
 85	size_t name_size;
 86	char *name;
 87	int err;
 88	bool res;
 89
 90	buf->filldir_called++;
 91	err = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
 92						   buf->sb, lower_name,
 93						   lower_namelen);
 94	if (err) {
 95		if (err != -EINVAL) {
 96			ecryptfs_printk(KERN_DEBUG,
 97					"%s: Error attempting to decode and decrypt filename [%s]; rc = [%d]\n",
 98					__func__, lower_name, err);
 99			return false;
100		}
101
102		/* Mask -EINVAL errors as these are most likely due a plaintext
103		 * filename present in the lower filesystem despite filename
104		 * encryption being enabled. One unavoidable example would be
105		 * the "lost+found" dentry in the root directory of an Ext4
106		 * filesystem.
107		 */
108		return true;
109	}
110
111	buf->caller->pos = buf->ctx.pos;
112	res = dir_emit(buf->caller, name, name_size, ino, d_type);
113	kfree(name);
114	if (res)
115		buf->entries_written++;
116	return res;
117}
118
119/**
120 * ecryptfs_readdir
121 * @file: The eCryptfs directory file
122 * @ctx: The actor to feed the entries to
123 */
124static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
125{
126	int rc;
127	struct file *lower_file;
128	struct inode *inode = file_inode(file);
129	struct ecryptfs_getdents_callback buf = {
130		.ctx.actor = ecryptfs_filldir,
131		.caller = ctx,
132		.sb = inode->i_sb,
133	};
134	lower_file = ecryptfs_file_to_lower(file);
135	rc = iterate_dir(lower_file, &buf.ctx);
136	ctx->pos = buf.ctx.pos;
137	if (rc >= 0 && (buf.entries_written || !buf.filldir_called))
138		fsstack_copy_attr_atime(inode, file_inode(lower_file));
139	return rc;
140}
141
142struct kmem_cache *ecryptfs_file_info_cache;
143
144static int read_or_initialize_metadata(struct dentry *dentry)
145{
146	struct inode *inode = d_inode(dentry);
147	struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
148	struct ecryptfs_crypt_stat *crypt_stat;
149	int rc;
150
151	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
152	mount_crypt_stat = &ecryptfs_superblock_to_private(
153						inode->i_sb)->mount_crypt_stat;
154	mutex_lock(&crypt_stat->cs_mutex);
155
156	if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
157	    crypt_stat->flags & ECRYPTFS_KEY_VALID) {
158		rc = 0;
159		goto out;
160	}
161
162	rc = ecryptfs_read_metadata(dentry);
163	if (!rc)
164		goto out;
165
166	if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
167		crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
168				       | ECRYPTFS_ENCRYPTED);
169		rc = 0;
170		goto out;
171	}
172
173	if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
174	    !i_size_read(ecryptfs_inode_to_lower(inode))) {
175		rc = ecryptfs_initialize_file(dentry, inode);
176		if (!rc)
177			goto out;
178	}
179
180	rc = -EIO;
181out:
182	mutex_unlock(&crypt_stat->cs_mutex);
183	return rc;
184}
185
186static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
187{
188	struct file *lower_file = ecryptfs_file_to_lower(file);
189	/*
190	 * Don't allow mmap on top of file systems that don't support it
191	 * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
192	 * allows recursive mounting, this will need to be extended.
193	 */
194	if (!can_mmap_file(lower_file))
195		return -ENODEV;
196	return generic_file_mmap(file, vma);
197}
198
199/**
200 * ecryptfs_open
201 * @inode: inode specifying file to open
202 * @file: Structure to return filled in
203 *
204 * Opens the file specified by inode.
205 *
206 * Returns zero on success; non-zero otherwise
207 */
208static int ecryptfs_open(struct inode *inode, struct file *file)
209{
210	int rc = 0;
211	struct ecryptfs_crypt_stat *crypt_stat = NULL;
212	struct dentry *ecryptfs_dentry = file->f_path.dentry;
213	/* Private value of ecryptfs_dentry allocated in
214	 * ecryptfs_lookup() */
215	struct ecryptfs_file_info *file_info;
216
217	/* Released in ecryptfs_release or end of function if failure */
218	file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
219	ecryptfs_set_file_private(file, file_info);
220	if (!file_info) {
221		ecryptfs_printk(KERN_ERR,
222				"Error attempting to allocate memory\n");
223		rc = -ENOMEM;
224		goto out;
225	}
226	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
227	mutex_lock(&crypt_stat->cs_mutex);
228	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
229		ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
230		/* Policy code enabled in future release */
231		crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
232				      | ECRYPTFS_ENCRYPTED);
233	}
234	mutex_unlock(&crypt_stat->cs_mutex);
235	rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
236	if (rc) {
237		printk(KERN_ERR "%s: Error attempting to initialize "
238			"the lower file for the dentry with name "
239			"[%pd]; rc = [%d]\n", __func__,
240			ecryptfs_dentry, rc);
241		goto out_free;
242	}
243	if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
244	    == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
245		rc = -EPERM;
246		printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
247		       "file must hence be opened RO\n", __func__);
248		goto out_put;
249	}
250	ecryptfs_set_file_lower(
251		file, ecryptfs_inode_to_private(inode)->lower_file);
252	rc = read_or_initialize_metadata(ecryptfs_dentry);
253	if (rc)
254		goto out_put;
255	ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
256			"[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
257			(unsigned long long)i_size_read(inode));
258	goto out;
259out_put:
260	ecryptfs_put_lower_file(inode);
261out_free:
262	kmem_cache_free(ecryptfs_file_info_cache,
263			ecryptfs_file_to_private(file));
264out:
265	return rc;
266}
267
268/**
269 * ecryptfs_dir_open
270 * @inode: inode specifying file to open
271 * @file: Structure to return filled in
272 *
273 * Opens the file specified by inode.
274 *
275 * Returns zero on success; non-zero otherwise
276 */
277static int ecryptfs_dir_open(struct inode *inode, struct file *file)
278{
279	struct dentry *ecryptfs_dentry = file->f_path.dentry;
280	/* Private value of ecryptfs_dentry allocated in
281	 * ecryptfs_lookup() */
282	struct ecryptfs_file_info *file_info;
283	struct file *lower_file;
284	struct path path;
285
286	/* Released in ecryptfs_release or end of function if failure */
287	file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
288	ecryptfs_set_file_private(file, file_info);
289	if (unlikely(!file_info)) {
290		ecryptfs_printk(KERN_ERR,
291				"Error attempting to allocate memory\n");
292		return -ENOMEM;
293	}
294	path = ecryptfs_lower_path(ecryptfs_dentry);
295	lower_file = dentry_open(&path, file->f_flags, current_cred());
296	if (IS_ERR(lower_file)) {
297		printk(KERN_ERR "%s: Error attempting to initialize "
298			"the lower file for the dentry with name "
299			"[%pd]; rc = [%ld]\n", __func__,
300			ecryptfs_dentry, PTR_ERR(lower_file));
301		kmem_cache_free(ecryptfs_file_info_cache, file_info);
302		return PTR_ERR(lower_file);
303	}
304	ecryptfs_set_file_lower(file, lower_file);
305	return 0;
306}
307
308static int ecryptfs_flush(struct file *file, fl_owner_t td)
309{
310	struct file *lower_file = ecryptfs_file_to_lower(file);
311
312	if (lower_file->f_op->flush) {
313		filemap_write_and_wait(file->f_mapping);
314		return lower_file->f_op->flush(lower_file, td);
315	}
316
317	return 0;
318}
319
320static int ecryptfs_release(struct inode *inode, struct file *file)
321{
322	ecryptfs_put_lower_file(inode);
323	kmem_cache_free(ecryptfs_file_info_cache,
324			ecryptfs_file_to_private(file));
325	return 0;
326}
327
328static int ecryptfs_dir_release(struct inode *inode, struct file *file)
329{
330	fput(ecryptfs_file_to_lower(file));
331	kmem_cache_free(ecryptfs_file_info_cache,
332			ecryptfs_file_to_private(file));
333	return 0;
334}
335
336static loff_t ecryptfs_dir_llseek(struct file *file, loff_t offset, int whence)
337{
338	return vfs_llseek(ecryptfs_file_to_lower(file), offset, whence);
339}
340
341static int
342ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
343{
344	int rc;
345
346	rc = file_write_and_wait(file);
347	if (rc)
348		return rc;
349
350	return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
351}
352
353static int ecryptfs_fasync(int fd, struct file *file, int flag)
354{
355	int rc = 0;
356	struct file *lower_file = NULL;
357
358	lower_file = ecryptfs_file_to_lower(file);
359	if (lower_file->f_op->fasync)
360		rc = lower_file->f_op->fasync(fd, lower_file, flag);
361	return rc;
362}
363
364static long
365ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
366{
367	struct file *lower_file = ecryptfs_file_to_lower(file);
368	long rc = -ENOTTY;
369
370	if (!lower_file->f_op->unlocked_ioctl)
371		return rc;
372
373	switch (cmd) {
374	case FITRIM:
375	case FS_IOC_GETFLAGS:
376	case FS_IOC_SETFLAGS:
377	case FS_IOC_GETVERSION:
378	case FS_IOC_SETVERSION:
379		rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
380		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
381
382		return rc;
383	default:
384		return rc;
385	}
386}
387
388#ifdef CONFIG_COMPAT
389static long
390ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
391{
392	struct file *lower_file = ecryptfs_file_to_lower(file);
393	long rc = -ENOIOCTLCMD;
394
395	if (!lower_file->f_op->compat_ioctl)
396		return rc;
397
398	switch (cmd) {
399	case FITRIM:
400	case FS_IOC32_GETFLAGS:
401	case FS_IOC32_SETFLAGS:
402	case FS_IOC32_GETVERSION:
403	case FS_IOC32_SETVERSION:
404		rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
405		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
406
407		return rc;
408	default:
409		return rc;
410	}
411}
412#endif
413
414const struct file_operations ecryptfs_dir_fops = {
415	.iterate_shared = ecryptfs_readdir,
416	.read = generic_read_dir,
417	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
418#ifdef CONFIG_COMPAT
419	.compat_ioctl = ecryptfs_compat_ioctl,
420#endif
421	.open = ecryptfs_dir_open,
422	.release = ecryptfs_dir_release,
423	.fsync = ecryptfs_fsync,
424	.llseek = ecryptfs_dir_llseek,
425};
426
427const struct file_operations ecryptfs_main_fops = {
428	.llseek = generic_file_llseek,
429	.read_iter = ecryptfs_read_update_atime,
430	.write_iter = generic_file_write_iter,
431	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
432#ifdef CONFIG_COMPAT
433	.compat_ioctl = ecryptfs_compat_ioctl,
434#endif
435	.mmap = ecryptfs_mmap,
436	.open = ecryptfs_open,
437	.flush = ecryptfs_flush,
438	.release = ecryptfs_release,
439	.fsync = ecryptfs_fsync,
440	.fasync = ecryptfs_fasync,
441	.splice_read = ecryptfs_splice_read_update_atime,
442};