xref: /linux/fs/cachefiles/daemon.c (revision 59e6295fac26b8e85c1ea859cdd89fa1e47519d7) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Daemon interface
3  *
4  * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  */
7 
8 #include <linux/module.h>
9 #include <linux/init.h>
10 #include <linux/sched.h>
11 #include <linux/completion.h>
12 #include <linux/slab.h>
13 #include <linux/fs.h>
14 #include <linux/file.h>
15 #include <linux/namei.h>
16 #include <linux/poll.h>
17 #include <linux/mount.h>
18 #include <linux/security.h>
19 #include <linux/statfs.h>
20 #include <linux/ctype.h>
21 #include <linux/string.h>
22 #include <linux/fs_struct.h>
23 #include "internal.h"
24 
25 static int cachefiles_daemon_open(struct inode *, struct file *);
26 static int cachefiles_daemon_release(struct inode *, struct file *);
27 static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
28 				      loff_t *);
29 static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
30 				       size_t, loff_t *);
31 static __poll_t cachefiles_daemon_poll(struct file *,
32 					   struct poll_table_struct *);
33 static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
34 static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
35 static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
36 static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
37 static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
38 static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
39 static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
40 static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
41 static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
42 static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
43 static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
44 static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
45 static int cachefiles_daemon_bind(struct cachefiles_cache *, char *);
46 static void cachefiles_daemon_unbind(struct cachefiles_cache *);
47 
48 static unsigned long cachefiles_open;
49 
50 const struct file_operations cachefiles_daemon_fops = {
51 	.owner		= THIS_MODULE,
52 	.open		= cachefiles_daemon_open,
53 	.release	= cachefiles_daemon_release,
54 	.read		= cachefiles_daemon_read,
55 	.write		= cachefiles_daemon_write,
56 	.poll		= cachefiles_daemon_poll,
57 	.llseek		= noop_llseek,
58 };
59 
60 struct cachefiles_daemon_cmd {
61 	char name[8];
62 	int (*handler)(struct cachefiles_cache *cache, char *args);
63 };
64 
65 static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
66 	{ "bind",	cachefiles_daemon_bind		},
67 	{ "brun",	cachefiles_daemon_brun		},
68 	{ "bcull",	cachefiles_daemon_bcull		},
69 	{ "bstop",	cachefiles_daemon_bstop		},
70 	{ "cull",	cachefiles_daemon_cull		},
71 	{ "debug",	cachefiles_daemon_debug		},
72 	{ "dir",	cachefiles_daemon_dir		},
73 	{ "frun",	cachefiles_daemon_frun		},
74 	{ "fcull",	cachefiles_daemon_fcull		},
75 	{ "fstop",	cachefiles_daemon_fstop		},
76 	{ "inuse",	cachefiles_daemon_inuse		},
77 	{ "secctx",	cachefiles_daemon_secctx	},
78 	{ "tag",	cachefiles_daemon_tag		},
79 	{ "",		NULL				}
80 };
81 
82 
83 /*
84  * Prepare a cache for caching.
85  */
86 static int cachefiles_daemon_open(struct inode *inode, struct file *file)
87 {
88 	struct cachefiles_cache *cache;
89 
90 	_enter("");
91 
92 	/* only the superuser may do this */
93 	if (!capable(CAP_SYS_ADMIN))
94 		return -EPERM;
95 
96 	/* the cachefiles device may only be open once at a time */
97 	if (xchg(&cachefiles_open, 1) == 1)
98 		return -EBUSY;
99 
100 	/* allocate a cache record */
101 	cache = kzalloc_obj(struct cachefiles_cache);
102 	if (!cache) {
103 		cachefiles_open = 0;
104 		return -ENOMEM;
105 	}
106 
107 	mutex_init(&cache->daemon_mutex);
108 	init_waitqueue_head(&cache->daemon_pollwq);
109 	INIT_LIST_HEAD(&cache->volumes);
110 	INIT_LIST_HEAD(&cache->object_list);
111 	spin_lock_init(&cache->object_list_lock);
112 
113 	/* set default caching limits
114 	 * - limit at 1% free space and/or free files
115 	 * - cull below 5% free space and/or free files
116 	 * - cease culling above 7% free space and/or free files
117 	 */
118 	cache->frun_percent = 7;
119 	cache->fcull_percent = 5;
120 	cache->fstop_percent = 1;
121 	cache->brun_percent = 7;
122 	cache->bcull_percent = 5;
123 	cache->bstop_percent = 1;
124 
125 	file->private_data = cache;
126 	cache->cachefilesd = file;
127 	return 0;
128 }
129 
130 /*
131  * Release a cache.
132  */
133 static int cachefiles_daemon_release(struct inode *inode, struct file *file)
134 {
135 	struct cachefiles_cache *cache = file->private_data;
136 
137 	_enter("");
138 
139 	ASSERT(cache);
140 
141 	set_bit(CACHEFILES_DEAD, &cache->flags);
142 	cachefiles_daemon_unbind(cache);
143 
144 	/* clean up the control file interface */
145 	cache->cachefilesd = NULL;
146 	file->private_data = NULL;
147 	cachefiles_open = 0;
148 
149 	kfree(cache);
150 	_leave("");
151 	return 0;
152 }
153 
154 static ssize_t cachefiles_do_daemon_read(struct cachefiles_cache *cache,
155 					 char __user *_buffer, size_t buflen)
156 {
157 	unsigned long long b_released;
158 	unsigned f_released;
159 	char buffer[256];
160 	int n;
161 
162 	/* check how much space the cache has */
163 	cachefiles_has_space(cache, 0, 0, cachefiles_has_space_check);
164 
165 	/* summarise */
166 	f_released = atomic_xchg(&cache->f_released, 0);
167 	b_released = atomic_long_xchg(&cache->b_released, 0);
168 	clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
169 
170 	n = snprintf(buffer, sizeof(buffer),
171 		     "cull=%c"
172 		     " frun=%llx"
173 		     " fcull=%llx"
174 		     " fstop=%llx"
175 		     " brun=%llx"
176 		     " bcull=%llx"
177 		     " bstop=%llx"
178 		     " freleased=%x"
179 		     " breleased=%llx",
180 		     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
181 		     (unsigned long long) cache->frun,
182 		     (unsigned long long) cache->fcull,
183 		     (unsigned long long) cache->fstop,
184 		     (unsigned long long) cache->brun,
185 		     (unsigned long long) cache->bcull,
186 		     (unsigned long long) cache->bstop,
187 		     f_released,
188 		     b_released);
189 
190 	if (n > buflen)
191 		return -EMSGSIZE;
192 
193 	if (copy_to_user(_buffer, buffer, n) != 0)
194 		return -EFAULT;
195 
196 	return n;
197 }
198 
199 /*
200  * Read the cache state.
201  */
202 static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
203 				      size_t buflen, loff_t *pos)
204 {
205 	struct cachefiles_cache *cache = file->private_data;
206 
207 	//_enter(",,%zu,", buflen);
208 
209 	if (!test_bit(CACHEFILES_READY, &cache->flags))
210 		return 0;
211 
212 	return cachefiles_do_daemon_read(cache, _buffer, buflen);
213 }
214 
215 /*
216  * Take a command from cachefilesd, parse it and act on it.
217  */
218 static ssize_t cachefiles_daemon_write(struct file *file,
219 				       const char __user *_data,
220 				       size_t datalen,
221 				       loff_t *pos)
222 {
223 	const struct cachefiles_daemon_cmd *cmd;
224 	struct cachefiles_cache *cache = file->private_data;
225 	ssize_t ret;
226 	char *data, *args, *cp;
227 
228 	//_enter(",,%zu,", datalen);
229 
230 	ASSERT(cache);
231 
232 	if (test_bit(CACHEFILES_DEAD, &cache->flags))
233 		return -EIO;
234 
235 	if (datalen > PAGE_SIZE - 1)
236 		return -EOPNOTSUPP;
237 
238 	/* drag the command string into the kernel so we can parse it */
239 	data = memdup_user_nul(_data, datalen);
240 	if (IS_ERR(data))
241 		return PTR_ERR(data);
242 
243 	ret = -EINVAL;
244 	if (memchr(data, '\0', datalen))
245 		goto error;
246 
247 	/* strip any newline */
248 	cp = memchr(data, '\n', datalen);
249 	if (cp) {
250 		if (cp == data)
251 			goto error;
252 
253 		*cp = '\0';
254 	}
255 
256 	/* parse the command */
257 	ret = -EOPNOTSUPP;
258 
259 	for (args = data; *args; args++)
260 		if (isspace(*args))
261 			break;
262 	if (*args) {
263 		if (args == data)
264 			goto error;
265 		*args = '\0';
266 		args = skip_spaces(++args);
267 	}
268 
269 	/* run the appropriate command handler */
270 	for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
271 		if (strcmp(cmd->name, data) == 0)
272 			goto found_command;
273 
274 error:
275 	kfree(data);
276 	//_leave(" = %zd", ret);
277 	return ret;
278 
279 found_command:
280 	mutex_lock(&cache->daemon_mutex);
281 
282 	ret = -EIO;
283 	if (!test_bit(CACHEFILES_DEAD, &cache->flags))
284 		ret = cmd->handler(cache, args);
285 
286 	mutex_unlock(&cache->daemon_mutex);
287 
288 	if (ret == 0)
289 		ret = datalen;
290 	goto error;
291 }
292 
293 /*
294  * Poll for culling state
295  * - use EPOLLOUT to indicate culling state
296  */
297 static __poll_t cachefiles_daemon_poll(struct file *file,
298 					   struct poll_table_struct *poll)
299 {
300 	struct cachefiles_cache *cache = file->private_data;
301 	__poll_t mask;
302 
303 	poll_wait(file, &cache->daemon_pollwq, poll);
304 	mask = 0;
305 
306 	if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
307 		mask |= EPOLLIN;
308 
309 	if (test_bit(CACHEFILES_CULLING, &cache->flags))
310 		mask |= EPOLLOUT;
311 
312 	return mask;
313 }
314 
315 /*
316  * Give a range error for cache space constraints
317  * - can be tail-called
318  */
319 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
320 					 char *args)
321 {
322 	pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
323 
324 	return -EINVAL;
325 }
326 
327 /*
328  * Set the percentage of files at which to stop culling
329  * - command: "frun <N>%"
330  */
331 static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
332 {
333 	unsigned long frun;
334 
335 	_enter(",%s", args);
336 
337 	if (!*args)
338 		return -EINVAL;
339 
340 	frun = simple_strtoul(args, &args, 10);
341 	if (args[0] != '%' || args[1] != '\0')
342 		return -EINVAL;
343 
344 	if (frun <= cache->fcull_percent || frun >= 100)
345 		return cachefiles_daemon_range_error(cache, args);
346 
347 	cache->frun_percent = frun;
348 	return 0;
349 }
350 
351 /*
352  * Set the percentage of files at which to start culling
353  * - command: "fcull <N>%"
354  */
355 static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
356 {
357 	unsigned long fcull;
358 
359 	_enter(",%s", args);
360 
361 	if (!*args)
362 		return -EINVAL;
363 
364 	fcull = simple_strtoul(args, &args, 10);
365 	if (args[0] != '%' || args[1] != '\0')
366 		return -EINVAL;
367 
368 	if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
369 		return cachefiles_daemon_range_error(cache, args);
370 
371 	cache->fcull_percent = fcull;
372 	return 0;
373 }
374 
375 /*
376  * Set the percentage of files at which to stop allocating
377  * - command: "fstop <N>%"
378  */
379 static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
380 {
381 	unsigned long fstop;
382 
383 	_enter(",%s", args);
384 
385 	if (!*args)
386 		return -EINVAL;
387 
388 	fstop = simple_strtoul(args, &args, 10);
389 	if (args[0] != '%' || args[1] != '\0')
390 		return -EINVAL;
391 
392 	if (fstop >= cache->fcull_percent)
393 		return cachefiles_daemon_range_error(cache, args);
394 
395 	cache->fstop_percent = fstop;
396 	return 0;
397 }
398 
399 /*
400  * Set the percentage of blocks at which to stop culling
401  * - command: "brun <N>%"
402  */
403 static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
404 {
405 	unsigned long brun;
406 
407 	_enter(",%s", args);
408 
409 	if (!*args)
410 		return -EINVAL;
411 
412 	brun = simple_strtoul(args, &args, 10);
413 	if (args[0] != '%' || args[1] != '\0')
414 		return -EINVAL;
415 
416 	if (brun <= cache->bcull_percent || brun >= 100)
417 		return cachefiles_daemon_range_error(cache, args);
418 
419 	cache->brun_percent = brun;
420 	return 0;
421 }
422 
423 /*
424  * Set the percentage of blocks at which to start culling
425  * - command: "bcull <N>%"
426  */
427 static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
428 {
429 	unsigned long bcull;
430 
431 	_enter(",%s", args);
432 
433 	if (!*args)
434 		return -EINVAL;
435 
436 	bcull = simple_strtoul(args, &args, 10);
437 	if (args[0] != '%' || args[1] != '\0')
438 		return -EINVAL;
439 
440 	if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
441 		return cachefiles_daemon_range_error(cache, args);
442 
443 	cache->bcull_percent = bcull;
444 	return 0;
445 }
446 
447 /*
448  * Set the percentage of blocks at which to stop allocating
449  * - command: "bstop <N>%"
450  */
451 static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
452 {
453 	unsigned long bstop;
454 
455 	_enter(",%s", args);
456 
457 	if (!*args)
458 		return -EINVAL;
459 
460 	bstop = simple_strtoul(args, &args, 10);
461 	if (args[0] != '%' || args[1] != '\0')
462 		return -EINVAL;
463 
464 	if (bstop >= cache->bcull_percent)
465 		return cachefiles_daemon_range_error(cache, args);
466 
467 	cache->bstop_percent = bstop;
468 	return 0;
469 }
470 
471 /*
472  * Set the cache directory
473  * - command: "dir <name>"
474  */
475 static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
476 {
477 	char *dir;
478 
479 	_enter(",%s", args);
480 
481 	if (!*args) {
482 		pr_err("Empty directory specified\n");
483 		return -EINVAL;
484 	}
485 
486 	if (cache->rootdirname) {
487 		pr_err("Second cache directory specified\n");
488 		return -EEXIST;
489 	}
490 
491 	dir = kstrdup(args, GFP_KERNEL);
492 	if (!dir)
493 		return -ENOMEM;
494 
495 	cache->rootdirname = dir;
496 	return 0;
497 }
498 
499 /*
500  * Set the cache security context
501  * - command: "secctx <ctx>"
502  */
503 static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
504 {
505 	int err;
506 
507 	_enter(",%s", args);
508 
509 	if (!*args) {
510 		pr_err("Empty security context specified\n");
511 		return -EINVAL;
512 	}
513 
514 	if (cache->have_secid) {
515 		pr_err("Second security context specified\n");
516 		return -EINVAL;
517 	}
518 
519 	err = security_secctx_to_secid(args, strlen(args), &cache->secid);
520 	if (err)
521 		return err;
522 
523 	cache->have_secid = true;
524 	return 0;
525 }
526 
527 /*
528  * Set the cache tag
529  * - command: "tag <name>"
530  */
531 static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
532 {
533 	char *tag;
534 
535 	_enter(",%s", args);
536 
537 	if (!*args) {
538 		pr_err("Empty tag specified\n");
539 		return -EINVAL;
540 	}
541 
542 	if (cache->tag)
543 		return -EEXIST;
544 
545 	tag = kstrdup(args, GFP_KERNEL);
546 	if (!tag)
547 		return -ENOMEM;
548 
549 	cache->tag = tag;
550 	return 0;
551 }
552 
553 /*
554  * Request a node in the cache be culled from the current working directory
555  * - command: "cull <name>"
556  */
557 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
558 {
559 	struct path path;
560 	const struct cred *saved_cred;
561 	int ret;
562 
563 	_enter(",%s", args);
564 
565 	if (strchr(args, '/'))
566 		goto inval;
567 
568 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
569 		pr_err("cull applied to unready cache\n");
570 		return -EIO;
571 	}
572 
573 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
574 		pr_err("cull applied to dead cache\n");
575 		return -EIO;
576 	}
577 
578 	get_fs_pwd(current->fs, &path);
579 
580 	if (!d_can_lookup(path.dentry))
581 		goto notdir;
582 
583 	cachefiles_begin_secure(cache, &saved_cred);
584 	ret = cachefiles_cull(cache, path.dentry, args);
585 	cachefiles_end_secure(cache, saved_cred);
586 
587 	path_put(&path);
588 	_leave(" = %d", ret);
589 	return ret;
590 
591 notdir:
592 	path_put(&path);
593 	pr_err("cull command requires dirfd to be a directory\n");
594 	return -ENOTDIR;
595 
596 inval:
597 	pr_err("cull command requires dirfd and filename\n");
598 	return -EINVAL;
599 }
600 
601 /*
602  * Set debugging mode
603  * - command: "debug <mask>"
604  */
605 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
606 {
607 	unsigned long mask;
608 
609 	_enter(",%s", args);
610 
611 	mask = simple_strtoul(args, &args, 0);
612 	if (args[0] != '\0')
613 		goto inval;
614 
615 	cachefiles_debug = mask;
616 	_leave(" = 0");
617 	return 0;
618 
619 inval:
620 	pr_err("debug command requires mask\n");
621 	return -EINVAL;
622 }
623 
624 /*
625  * Find out whether an object in the current working directory is in use or not
626  * - command: "inuse <name>"
627  */
628 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
629 {
630 	struct path path;
631 	const struct cred *saved_cred;
632 	int ret;
633 
634 	//_enter(",%s", args);
635 
636 	if (strchr(args, '/'))
637 		goto inval;
638 
639 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
640 		pr_err("inuse applied to unready cache\n");
641 		return -EIO;
642 	}
643 
644 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
645 		pr_err("inuse applied to dead cache\n");
646 		return -EIO;
647 	}
648 
649 	get_fs_pwd(current->fs, &path);
650 
651 	if (!d_can_lookup(path.dentry))
652 		goto notdir;
653 
654 	cachefiles_begin_secure(cache, &saved_cred);
655 	ret = cachefiles_check_in_use(cache, path.dentry, args);
656 	cachefiles_end_secure(cache, saved_cred);
657 
658 	path_put(&path);
659 	//_leave(" = %d", ret);
660 	return ret;
661 
662 notdir:
663 	path_put(&path);
664 	pr_err("inuse command requires dirfd to be a directory\n");
665 	return -ENOTDIR;
666 
667 inval:
668 	pr_err("inuse command requires dirfd and filename\n");
669 	return -EINVAL;
670 }
671 
672 /*
673  * Bind a directory as a cache
674  */
675 static int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
676 {
677 	_enter("{%u,%u,%u,%u,%u,%u},%s",
678 	       cache->frun_percent,
679 	       cache->fcull_percent,
680 	       cache->fstop_percent,
681 	       cache->brun_percent,
682 	       cache->bcull_percent,
683 	       cache->bstop_percent,
684 	       args);
685 
686 	if (cache->fstop_percent >= cache->fcull_percent ||
687 	    cache->fcull_percent >= cache->frun_percent ||
688 	    cache->frun_percent  >= 100)
689 		return -ERANGE;
690 
691 	if (cache->bstop_percent >= cache->bcull_percent ||
692 	    cache->bcull_percent >= cache->brun_percent ||
693 	    cache->brun_percent  >= 100)
694 		return -ERANGE;
695 
696 	if (!cache->rootdirname) {
697 		pr_err("No cache directory specified\n");
698 		return -EINVAL;
699 	}
700 
701 	/* Don't permit already bound caches to be re-bound */
702 	if (test_bit(CACHEFILES_READY, &cache->flags)) {
703 		pr_err("Cache already bound\n");
704 		return -EBUSY;
705 	}
706 
707 	if (*args) {
708 		pr_err("'bind' command doesn't take an argument\n");
709 		return -EINVAL;
710 	}
711 
712 	/* Make sure we have copies of the tag string */
713 	if (!cache->tag) {
714 		/*
715 		 * The tag string is released by the fops->release()
716 		 * function, so we don't release it on error here
717 		 */
718 		cache->tag = kstrdup("CacheFiles", GFP_KERNEL);
719 		if (!cache->tag)
720 			return -ENOMEM;
721 	}
722 
723 	return cachefiles_add_cache(cache);
724 }
725 
726 /*
727  * Unbind a cache.
728  */
729 static void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
730 {
731 	_enter("");
732 
733 	if (test_bit(CACHEFILES_READY, &cache->flags))
734 		cachefiles_withdraw_cache(cache);
735 
736 	cachefiles_put_directory(cache->graveyard);
737 	cachefiles_put_directory(cache->store);
738 	mntput(cache->mnt);
739 	put_cred(cache->cache_cred);
740 
741 	kfree(cache->rootdirname);
742 	kfree(cache->tag);
743 
744 	_leave("");
745 }
746