xref: /linux/fs/cachefiles/daemon.c (revision aa23aa55166c2865ac430168c4b9d405cf8c6980) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Daemon interface
3  *
4  * Copyright (C) 2007 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/statfs.h>
19 #include <linux/ctype.h>
20 #include <linux/string.h>
21 #include <linux/fs_struct.h>
22 #include "internal.h"
23 
24 static int cachefiles_daemon_open(struct inode *, struct file *);
25 static int cachefiles_daemon_release(struct inode *, struct file *);
26 static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
27 				      loff_t *);
28 static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
29 				       size_t, loff_t *);
30 static __poll_t cachefiles_daemon_poll(struct file *,
31 					   struct poll_table_struct *);
32 static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
33 static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
34 static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
35 static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
36 static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
37 static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
38 static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
39 static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
40 static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
41 static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
42 static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
43 static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
44 
45 static unsigned long cachefiles_open;
46 
47 const struct file_operations cachefiles_daemon_fops = {
48 	.owner		= THIS_MODULE,
49 	.open		= cachefiles_daemon_open,
50 	.release	= cachefiles_daemon_release,
51 	.read		= cachefiles_daemon_read,
52 	.write		= cachefiles_daemon_write,
53 	.poll		= cachefiles_daemon_poll,
54 	.llseek		= noop_llseek,
55 };
56 
57 struct cachefiles_daemon_cmd {
58 	char name[8];
59 	int (*handler)(struct cachefiles_cache *cache, char *args);
60 };
61 
62 static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
63 	{ "bind",	cachefiles_daemon_bind		},
64 	{ "brun",	cachefiles_daemon_brun		},
65 	{ "bcull",	cachefiles_daemon_bcull		},
66 	{ "bstop",	cachefiles_daemon_bstop		},
67 	{ "cull",	cachefiles_daemon_cull		},
68 	{ "debug",	cachefiles_daemon_debug		},
69 	{ "dir",	cachefiles_daemon_dir		},
70 	{ "frun",	cachefiles_daemon_frun		},
71 	{ "fcull",	cachefiles_daemon_fcull		},
72 	{ "fstop",	cachefiles_daemon_fstop		},
73 	{ "inuse",	cachefiles_daemon_inuse		},
74 	{ "secctx",	cachefiles_daemon_secctx	},
75 	{ "tag",	cachefiles_daemon_tag		},
76 	{ "",		NULL				}
77 };
78 
79 
80 /*
81  * do various checks
82  */
83 static int cachefiles_daemon_open(struct inode *inode, struct file *file)
84 {
85 	struct cachefiles_cache *cache;
86 
87 	_enter("");
88 
89 	/* only the superuser may do this */
90 	if (!capable(CAP_SYS_ADMIN))
91 		return -EPERM;
92 
93 	/* the cachefiles device may only be open once at a time */
94 	if (xchg(&cachefiles_open, 1) == 1)
95 		return -EBUSY;
96 
97 	/* allocate a cache record */
98 	cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
99 	if (!cache) {
100 		cachefiles_open = 0;
101 		return -ENOMEM;
102 	}
103 
104 	mutex_init(&cache->daemon_mutex);
105 	cache->active_nodes = RB_ROOT;
106 	rwlock_init(&cache->active_lock);
107 	init_waitqueue_head(&cache->daemon_pollwq);
108 
109 	/* set default caching limits
110 	 * - limit at 1% free space and/or free files
111 	 * - cull below 5% free space and/or free files
112 	 * - cease culling above 7% free space and/or free files
113 	 */
114 	cache->frun_percent = 7;
115 	cache->fcull_percent = 5;
116 	cache->fstop_percent = 1;
117 	cache->brun_percent = 7;
118 	cache->bcull_percent = 5;
119 	cache->bstop_percent = 1;
120 
121 	file->private_data = cache;
122 	cache->cachefilesd = file;
123 	return 0;
124 }
125 
126 /*
127  * release a cache
128  */
129 static int cachefiles_daemon_release(struct inode *inode, struct file *file)
130 {
131 	struct cachefiles_cache *cache = file->private_data;
132 
133 	_enter("");
134 
135 	ASSERT(cache);
136 
137 	set_bit(CACHEFILES_DEAD, &cache->flags);
138 
139 	cachefiles_daemon_unbind(cache);
140 
141 	ASSERT(!cache->active_nodes.rb_node);
142 
143 	/* clean up the control file interface */
144 	cache->cachefilesd = NULL;
145 	file->private_data = NULL;
146 	cachefiles_open = 0;
147 
148 	kfree(cache);
149 
150 	_leave("");
151 	return 0;
152 }
153 
154 /*
155  * read the cache state
156  */
157 static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
158 				      size_t buflen, loff_t *pos)
159 {
160 	struct cachefiles_cache *cache = file->private_data;
161 	unsigned long long b_released;
162 	unsigned f_released;
163 	char buffer[256];
164 	int n;
165 
166 	//_enter(",,%zu,", buflen);
167 
168 	if (!test_bit(CACHEFILES_READY, &cache->flags))
169 		return 0;
170 
171 	/* check how much space the cache has */
172 	cachefiles_has_space(cache, 0, 0);
173 
174 	/* summarise */
175 	f_released = atomic_xchg(&cache->f_released, 0);
176 	b_released = atomic_long_xchg(&cache->b_released, 0);
177 	clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
178 
179 	n = snprintf(buffer, sizeof(buffer),
180 		     "cull=%c"
181 		     " frun=%llx"
182 		     " fcull=%llx"
183 		     " fstop=%llx"
184 		     " brun=%llx"
185 		     " bcull=%llx"
186 		     " bstop=%llx"
187 		     " freleased=%x"
188 		     " breleased=%llx",
189 		     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
190 		     (unsigned long long) cache->frun,
191 		     (unsigned long long) cache->fcull,
192 		     (unsigned long long) cache->fstop,
193 		     (unsigned long long) cache->brun,
194 		     (unsigned long long) cache->bcull,
195 		     (unsigned long long) cache->bstop,
196 		     f_released,
197 		     b_released);
198 
199 	if (n > buflen)
200 		return -EMSGSIZE;
201 
202 	if (copy_to_user(_buffer, buffer, n) != 0)
203 		return -EFAULT;
204 
205 	return n;
206 }
207 
208 /*
209  * command the cache
210  */
211 static ssize_t cachefiles_daemon_write(struct file *file,
212 				       const char __user *_data,
213 				       size_t datalen,
214 				       loff_t *pos)
215 {
216 	const struct cachefiles_daemon_cmd *cmd;
217 	struct cachefiles_cache *cache = file->private_data;
218 	ssize_t ret;
219 	char *data, *args, *cp;
220 
221 	//_enter(",,%zu,", datalen);
222 
223 	ASSERT(cache);
224 
225 	if (test_bit(CACHEFILES_DEAD, &cache->flags))
226 		return -EIO;
227 
228 	if (datalen < 0 || datalen > PAGE_SIZE - 1)
229 		return -EOPNOTSUPP;
230 
231 	/* drag the command string into the kernel so we can parse it */
232 	data = memdup_user_nul(_data, datalen);
233 	if (IS_ERR(data))
234 		return PTR_ERR(data);
235 
236 	ret = -EINVAL;
237 	if (memchr(data, '\0', datalen))
238 		goto error;
239 
240 	/* strip any newline */
241 	cp = memchr(data, '\n', datalen);
242 	if (cp) {
243 		if (cp == data)
244 			goto error;
245 
246 		*cp = '\0';
247 	}
248 
249 	/* parse the command */
250 	ret = -EOPNOTSUPP;
251 
252 	for (args = data; *args; args++)
253 		if (isspace(*args))
254 			break;
255 	if (*args) {
256 		if (args == data)
257 			goto error;
258 		*args = '\0';
259 		args = skip_spaces(++args);
260 	}
261 
262 	/* run the appropriate command handler */
263 	for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
264 		if (strcmp(cmd->name, data) == 0)
265 			goto found_command;
266 
267 error:
268 	kfree(data);
269 	//_leave(" = %zd", ret);
270 	return ret;
271 
272 found_command:
273 	mutex_lock(&cache->daemon_mutex);
274 
275 	ret = -EIO;
276 	if (!test_bit(CACHEFILES_DEAD, &cache->flags))
277 		ret = cmd->handler(cache, args);
278 
279 	mutex_unlock(&cache->daemon_mutex);
280 
281 	if (ret == 0)
282 		ret = datalen;
283 	goto error;
284 }
285 
286 /*
287  * poll for culling state
288  * - use EPOLLOUT to indicate culling state
289  */
290 static __poll_t cachefiles_daemon_poll(struct file *file,
291 					   struct poll_table_struct *poll)
292 {
293 	struct cachefiles_cache *cache = file->private_data;
294 	__poll_t mask;
295 
296 	poll_wait(file, &cache->daemon_pollwq, poll);
297 	mask = 0;
298 
299 	if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
300 		mask |= EPOLLIN;
301 
302 	if (test_bit(CACHEFILES_CULLING, &cache->flags))
303 		mask |= EPOLLOUT;
304 
305 	return mask;
306 }
307 
308 /*
309  * give a range error for cache space constraints
310  * - can be tail-called
311  */
312 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
313 					 char *args)
314 {
315 	pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
316 
317 	return -EINVAL;
318 }
319 
320 /*
321  * set the percentage of files at which to stop culling
322  * - command: "frun <N>%"
323  */
324 static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
325 {
326 	unsigned long frun;
327 
328 	_enter(",%s", args);
329 
330 	if (!*args)
331 		return -EINVAL;
332 
333 	frun = simple_strtoul(args, &args, 10);
334 	if (args[0] != '%' || args[1] != '\0')
335 		return -EINVAL;
336 
337 	if (frun <= cache->fcull_percent || frun >= 100)
338 		return cachefiles_daemon_range_error(cache, args);
339 
340 	cache->frun_percent = frun;
341 	return 0;
342 }
343 
344 /*
345  * set the percentage of files at which to start culling
346  * - command: "fcull <N>%"
347  */
348 static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
349 {
350 	unsigned long fcull;
351 
352 	_enter(",%s", args);
353 
354 	if (!*args)
355 		return -EINVAL;
356 
357 	fcull = simple_strtoul(args, &args, 10);
358 	if (args[0] != '%' || args[1] != '\0')
359 		return -EINVAL;
360 
361 	if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
362 		return cachefiles_daemon_range_error(cache, args);
363 
364 	cache->fcull_percent = fcull;
365 	return 0;
366 }
367 
368 /*
369  * set the percentage of files at which to stop allocating
370  * - command: "fstop <N>%"
371  */
372 static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
373 {
374 	unsigned long fstop;
375 
376 	_enter(",%s", args);
377 
378 	if (!*args)
379 		return -EINVAL;
380 
381 	fstop = simple_strtoul(args, &args, 10);
382 	if (args[0] != '%' || args[1] != '\0')
383 		return -EINVAL;
384 
385 	if (fstop < 0 || fstop >= cache->fcull_percent)
386 		return cachefiles_daemon_range_error(cache, args);
387 
388 	cache->fstop_percent = fstop;
389 	return 0;
390 }
391 
392 /*
393  * set the percentage of blocks at which to stop culling
394  * - command: "brun <N>%"
395  */
396 static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
397 {
398 	unsigned long brun;
399 
400 	_enter(",%s", args);
401 
402 	if (!*args)
403 		return -EINVAL;
404 
405 	brun = simple_strtoul(args, &args, 10);
406 	if (args[0] != '%' || args[1] != '\0')
407 		return -EINVAL;
408 
409 	if (brun <= cache->bcull_percent || brun >= 100)
410 		return cachefiles_daemon_range_error(cache, args);
411 
412 	cache->brun_percent = brun;
413 	return 0;
414 }
415 
416 /*
417  * set the percentage of blocks at which to start culling
418  * - command: "bcull <N>%"
419  */
420 static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
421 {
422 	unsigned long bcull;
423 
424 	_enter(",%s", args);
425 
426 	if (!*args)
427 		return -EINVAL;
428 
429 	bcull = simple_strtoul(args, &args, 10);
430 	if (args[0] != '%' || args[1] != '\0')
431 		return -EINVAL;
432 
433 	if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
434 		return cachefiles_daemon_range_error(cache, args);
435 
436 	cache->bcull_percent = bcull;
437 	return 0;
438 }
439 
440 /*
441  * set the percentage of blocks at which to stop allocating
442  * - command: "bstop <N>%"
443  */
444 static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
445 {
446 	unsigned long bstop;
447 
448 	_enter(",%s", args);
449 
450 	if (!*args)
451 		return -EINVAL;
452 
453 	bstop = simple_strtoul(args, &args, 10);
454 	if (args[0] != '%' || args[1] != '\0')
455 		return -EINVAL;
456 
457 	if (bstop < 0 || bstop >= cache->bcull_percent)
458 		return cachefiles_daemon_range_error(cache, args);
459 
460 	cache->bstop_percent = bstop;
461 	return 0;
462 }
463 
464 /*
465  * set the cache directory
466  * - command: "dir <name>"
467  */
468 static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
469 {
470 	char *dir;
471 
472 	_enter(",%s", args);
473 
474 	if (!*args) {
475 		pr_err("Empty directory specified\n");
476 		return -EINVAL;
477 	}
478 
479 	if (cache->rootdirname) {
480 		pr_err("Second cache directory specified\n");
481 		return -EEXIST;
482 	}
483 
484 	dir = kstrdup(args, GFP_KERNEL);
485 	if (!dir)
486 		return -ENOMEM;
487 
488 	cache->rootdirname = dir;
489 	return 0;
490 }
491 
492 /*
493  * set the cache security context
494  * - command: "secctx <ctx>"
495  */
496 static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
497 {
498 	char *secctx;
499 
500 	_enter(",%s", args);
501 
502 	if (!*args) {
503 		pr_err("Empty security context specified\n");
504 		return -EINVAL;
505 	}
506 
507 	if (cache->secctx) {
508 		pr_err("Second security context specified\n");
509 		return -EINVAL;
510 	}
511 
512 	secctx = kstrdup(args, GFP_KERNEL);
513 	if (!secctx)
514 		return -ENOMEM;
515 
516 	cache->secctx = secctx;
517 	return 0;
518 }
519 
520 /*
521  * set the cache tag
522  * - command: "tag <name>"
523  */
524 static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
525 {
526 	char *tag;
527 
528 	_enter(",%s", args);
529 
530 	if (!*args) {
531 		pr_err("Empty tag specified\n");
532 		return -EINVAL;
533 	}
534 
535 	if (cache->tag)
536 		return -EEXIST;
537 
538 	tag = kstrdup(args, GFP_KERNEL);
539 	if (!tag)
540 		return -ENOMEM;
541 
542 	cache->tag = tag;
543 	return 0;
544 }
545 
546 /*
547  * request a node in the cache be culled from the current working directory
548  * - command: "cull <name>"
549  */
550 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
551 {
552 	struct path path;
553 	const struct cred *saved_cred;
554 	int ret;
555 
556 	_enter(",%s", args);
557 
558 	if (strchr(args, '/'))
559 		goto inval;
560 
561 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
562 		pr_err("cull applied to unready cache\n");
563 		return -EIO;
564 	}
565 
566 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
567 		pr_err("cull applied to dead cache\n");
568 		return -EIO;
569 	}
570 
571 	/* extract the directory dentry from the cwd */
572 	get_fs_pwd(current->fs, &path);
573 
574 	if (!d_can_lookup(path.dentry))
575 		goto notdir;
576 
577 	cachefiles_begin_secure(cache, &saved_cred);
578 	ret = cachefiles_cull(cache, path.dentry, args);
579 	cachefiles_end_secure(cache, saved_cred);
580 
581 	path_put(&path);
582 	_leave(" = %d", ret);
583 	return ret;
584 
585 notdir:
586 	path_put(&path);
587 	pr_err("cull command requires dirfd to be a directory\n");
588 	return -ENOTDIR;
589 
590 inval:
591 	pr_err("cull command requires dirfd and filename\n");
592 	return -EINVAL;
593 }
594 
595 /*
596  * set debugging mode
597  * - command: "debug <mask>"
598  */
599 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
600 {
601 	unsigned long mask;
602 
603 	_enter(",%s", args);
604 
605 	mask = simple_strtoul(args, &args, 0);
606 	if (args[0] != '\0')
607 		goto inval;
608 
609 	cachefiles_debug = mask;
610 	_leave(" = 0");
611 	return 0;
612 
613 inval:
614 	pr_err("debug command requires mask\n");
615 	return -EINVAL;
616 }
617 
618 /*
619  * find out whether an object in the current working directory is in use or not
620  * - command: "inuse <name>"
621  */
622 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
623 {
624 	struct path path;
625 	const struct cred *saved_cred;
626 	int ret;
627 
628 	//_enter(",%s", args);
629 
630 	if (strchr(args, '/'))
631 		goto inval;
632 
633 	if (!test_bit(CACHEFILES_READY, &cache->flags)) {
634 		pr_err("inuse applied to unready cache\n");
635 		return -EIO;
636 	}
637 
638 	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
639 		pr_err("inuse applied to dead cache\n");
640 		return -EIO;
641 	}
642 
643 	/* extract the directory dentry from the cwd */
644 	get_fs_pwd(current->fs, &path);
645 
646 	if (!d_can_lookup(path.dentry))
647 		goto notdir;
648 
649 	cachefiles_begin_secure(cache, &saved_cred);
650 	ret = cachefiles_check_in_use(cache, path.dentry, args);
651 	cachefiles_end_secure(cache, saved_cred);
652 
653 	path_put(&path);
654 	//_leave(" = %d", ret);
655 	return ret;
656 
657 notdir:
658 	path_put(&path);
659 	pr_err("inuse command requires dirfd to be a directory\n");
660 	return -ENOTDIR;
661 
662 inval:
663 	pr_err("inuse command requires dirfd and filename\n");
664 	return -EINVAL;
665 }
666 
667 /*
668  * see if we have space for a number of pages and/or a number of files in the
669  * cache
670  */
671 int cachefiles_has_space(struct cachefiles_cache *cache,
672 			 unsigned fnr, unsigned bnr)
673 {
674 	struct kstatfs stats;
675 	struct path path = {
676 		.mnt	= cache->mnt,
677 		.dentry	= cache->mnt->mnt_root,
678 	};
679 	int ret;
680 
681 	//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
682 	//       (unsigned long long) cache->frun,
683 	//       (unsigned long long) cache->fcull,
684 	//       (unsigned long long) cache->fstop,
685 	//       (unsigned long long) cache->brun,
686 	//       (unsigned long long) cache->bcull,
687 	//       (unsigned long long) cache->bstop,
688 	//       fnr, bnr);
689 
690 	/* find out how many pages of blockdev are available */
691 	memset(&stats, 0, sizeof(stats));
692 
693 	ret = vfs_statfs(&path, &stats);
694 	if (ret < 0) {
695 		if (ret == -EIO)
696 			cachefiles_io_error(cache, "statfs failed");
697 		_leave(" = %d", ret);
698 		return ret;
699 	}
700 
701 	stats.f_bavail >>= cache->bshift;
702 
703 	//_debug("avail %llu,%llu",
704 	//       (unsigned long long) stats.f_ffree,
705 	//       (unsigned long long) stats.f_bavail);
706 
707 	/* see if there is sufficient space */
708 	if (stats.f_ffree > fnr)
709 		stats.f_ffree -= fnr;
710 	else
711 		stats.f_ffree = 0;
712 
713 	if (stats.f_bavail > bnr)
714 		stats.f_bavail -= bnr;
715 	else
716 		stats.f_bavail = 0;
717 
718 	ret = -ENOBUFS;
719 	if (stats.f_ffree < cache->fstop ||
720 	    stats.f_bavail < cache->bstop)
721 		goto begin_cull;
722 
723 	ret = 0;
724 	if (stats.f_ffree < cache->fcull ||
725 	    stats.f_bavail < cache->bcull)
726 		goto begin_cull;
727 
728 	if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
729 	    stats.f_ffree >= cache->frun &&
730 	    stats.f_bavail >= cache->brun &&
731 	    test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
732 	    ) {
733 		_debug("cease culling");
734 		cachefiles_state_changed(cache);
735 	}
736 
737 	//_leave(" = 0");
738 	return 0;
739 
740 begin_cull:
741 	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
742 		_debug("### CULL CACHE ###");
743 		cachefiles_state_changed(cache);
744 	}
745 
746 	_leave(" = %d", ret);
747 	return ret;
748 }
749