xref: /openbmc/linux/fs/ecryptfs/file.c (revision 9659281c) 
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