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Linux/fs/ecryptfs/file.c

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  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 

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