xref: /openbmc/linux/kernel/bpf/local_storage.c (revision 8dda2eac) 
1 //SPDX-License-Identifier: GPL-2.0
2 #include <linux/bpf-cgroup.h>
3 #include <linux/bpf.h>
4 #include <linux/btf.h>
5 #include <linux/bug.h>
6 #include <linux/filter.h>
7 #include <linux/mm.h>
8 #include <linux/rbtree.h>
9 #include <linux/slab.h>
10 #include <uapi/linux/btf.h>
11 
12 #ifdef CONFIG_CGROUP_BPF
13 
14 DEFINE_PER_CPU(struct bpf_cgroup_storage_info,
15 	       bpf_cgroup_storage_info[BPF_CGROUP_STORAGE_NEST_MAX]);
16 
17 #include "../cgroup/cgroup-internal.h"
18 
19 #define LOCAL_STORAGE_CREATE_FLAG_MASK					\
20 	(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)
21 
22 struct bpf_cgroup_storage_map {
23 	struct bpf_map map;
24 
25 	spinlock_t lock;
26 	struct rb_root root;
27 	struct list_head list;
28 };
29 
30 static struct bpf_cgroup_storage_map *map_to_storage(struct bpf_map *map)
31 {
32 	return container_of(map, struct bpf_cgroup_storage_map, map);
33 }
34 
35 static bool attach_type_isolated(const struct bpf_map *map)
36 {
37 	return map->key_size == sizeof(struct bpf_cgroup_storage_key);
38 }
39 
40 static int bpf_cgroup_storage_key_cmp(const struct bpf_cgroup_storage_map *map,
41 				      const void *_key1, const void *_key2)
42 {
43 	if (attach_type_isolated(&map->map)) {
44 		const struct bpf_cgroup_storage_key *key1 = _key1;
45 		const struct bpf_cgroup_storage_key *key2 = _key2;
46 
47 		if (key1->cgroup_inode_id < key2->cgroup_inode_id)
48 			return -1;
49 		else if (key1->cgroup_inode_id > key2->cgroup_inode_id)
50 			return 1;
51 		else if (key1->attach_type < key2->attach_type)
52 			return -1;
53 		else if (key1->attach_type > key2->attach_type)
54 			return 1;
55 	} else {
56 		const __u64 *cgroup_inode_id1 = _key1;
57 		const __u64 *cgroup_inode_id2 = _key2;
58 
59 		if (*cgroup_inode_id1 < *cgroup_inode_id2)
60 			return -1;
61 		else if (*cgroup_inode_id1 > *cgroup_inode_id2)
62 			return 1;
63 	}
64 	return 0;
65 }
66 
67 struct bpf_cgroup_storage *
68 cgroup_storage_lookup(struct bpf_cgroup_storage_map *map,
69 		      void *key, bool locked)
70 {
71 	struct rb_root *root = &map->root;
72 	struct rb_node *node;
73 
74 	if (!locked)
75 		spin_lock_bh(&map->lock);
76 
77 	node = root->rb_node;
78 	while (node) {
79 		struct bpf_cgroup_storage *storage;
80 
81 		storage = container_of(node, struct bpf_cgroup_storage, node);
82 
83 		switch (bpf_cgroup_storage_key_cmp(map, key, &storage->key)) {
84 		case -1:
85 			node = node->rb_left;
86 			break;
87 		case 1:
88 			node = node->rb_right;
89 			break;
90 		default:
91 			if (!locked)
92 				spin_unlock_bh(&map->lock);
93 			return storage;
94 		}
95 	}
96 
97 	if (!locked)
98 		spin_unlock_bh(&map->lock);
99 
100 	return NULL;
101 }
102 
103 static int cgroup_storage_insert(struct bpf_cgroup_storage_map *map,
104 				 struct bpf_cgroup_storage *storage)
105 {
106 	struct rb_root *root = &map->root;
107 	struct rb_node **new = &(root->rb_node), *parent = NULL;
108 
109 	while (*new) {
110 		struct bpf_cgroup_storage *this;
111 
112 		this = container_of(*new, struct bpf_cgroup_storage, node);
113 
114 		parent = *new;
115 		switch (bpf_cgroup_storage_key_cmp(map, &storage->key, &this->key)) {
116 		case -1:
117 			new = &((*new)->rb_left);
118 			break;
119 		case 1:
120 			new = &((*new)->rb_right);
121 			break;
122 		default:
123 			return -EEXIST;
124 		}
125 	}
126 
127 	rb_link_node(&storage->node, parent, new);
128 	rb_insert_color(&storage->node, root);
129 
130 	return 0;
131 }
132 
133 static void *cgroup_storage_lookup_elem(struct bpf_map *_map, void *key)
134 {
135 	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
136 	struct bpf_cgroup_storage *storage;
137 
138 	storage = cgroup_storage_lookup(map, key, false);
139 	if (!storage)
140 		return NULL;
141 
142 	return &READ_ONCE(storage->buf)->data[0];
143 }
144 
145 static int cgroup_storage_update_elem(struct bpf_map *map, void *key,
146 				      void *value, u64 flags)
147 {
148 	struct bpf_cgroup_storage *storage;
149 	struct bpf_storage_buffer *new;
150 
151 	if (unlikely(flags & ~(BPF_F_LOCK | BPF_EXIST)))
152 		return -EINVAL;
153 
154 	if (unlikely((flags & BPF_F_LOCK) &&
155 		     !map_value_has_spin_lock(map)))
156 		return -EINVAL;
157 
158 	storage = cgroup_storage_lookup((struct bpf_cgroup_storage_map *)map,
159 					key, false);
160 	if (!storage)
161 		return -ENOENT;
162 
163 	if (flags & BPF_F_LOCK) {
164 		copy_map_value_locked(map, storage->buf->data, value, false);
165 		return 0;
166 	}
167 
168 	new = bpf_map_kmalloc_node(map, sizeof(struct bpf_storage_buffer) +
169 				   map->value_size,
170 				   __GFP_ZERO | GFP_ATOMIC | __GFP_NOWARN,
171 				   map->numa_node);
172 	if (!new)
173 		return -ENOMEM;
174 
175 	memcpy(&new->data[0], value, map->value_size);
176 	check_and_init_map_lock(map, new->data);
177 
178 	new = xchg(&storage->buf, new);
179 	kfree_rcu(new, rcu);
180 
181 	return 0;
182 }
183 
184 int bpf_percpu_cgroup_storage_copy(struct bpf_map *_map, void *key,
185 				   void *value)
186 {
187 	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
188 	struct bpf_cgroup_storage *storage;
189 	int cpu, off = 0;
190 	u32 size;
191 
192 	rcu_read_lock();
193 	storage = cgroup_storage_lookup(map, key, false);
194 	if (!storage) {
195 		rcu_read_unlock();
196 		return -ENOENT;
197 	}
198 
199 	/* per_cpu areas are zero-filled and bpf programs can only
200 	 * access 'value_size' of them, so copying rounded areas
201 	 * will not leak any kernel data
202 	 */
203 	size = round_up(_map->value_size, 8);
204 	for_each_possible_cpu(cpu) {
205 		bpf_long_memcpy(value + off,
206 				per_cpu_ptr(storage->percpu_buf, cpu), size);
207 		off += size;
208 	}
209 	rcu_read_unlock();
210 	return 0;
211 }
212 
213 int bpf_percpu_cgroup_storage_update(struct bpf_map *_map, void *key,
214 				     void *value, u64 map_flags)
215 {
216 	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
217 	struct bpf_cgroup_storage *storage;
218 	int cpu, off = 0;
219 	u32 size;
220 
221 	if (map_flags != BPF_ANY && map_flags != BPF_EXIST)
222 		return -EINVAL;
223 
224 	rcu_read_lock();
225 	storage = cgroup_storage_lookup(map, key, false);
226 	if (!storage) {
227 		rcu_read_unlock();
228 		return -ENOENT;
229 	}
230 
231 	/* the user space will provide round_up(value_size, 8) bytes that
232 	 * will be copied into per-cpu area. bpf programs can only access
233 	 * value_size of it. During lookup the same extra bytes will be
234 	 * returned or zeros which were zero-filled by percpu_alloc,
235 	 * so no kernel data leaks possible
236 	 */
237 	size = round_up(_map->value_size, 8);
238 	for_each_possible_cpu(cpu) {
239 		bpf_long_memcpy(per_cpu_ptr(storage->percpu_buf, cpu),
240 				value + off, size);
241 		off += size;
242 	}
243 	rcu_read_unlock();
244 	return 0;
245 }
246 
247 static int cgroup_storage_get_next_key(struct bpf_map *_map, void *key,
248 				       void *_next_key)
249 {
250 	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
251 	struct bpf_cgroup_storage *storage;
252 
253 	spin_lock_bh(&map->lock);
254 
255 	if (list_empty(&map->list))
256 		goto enoent;
257 
258 	if (key) {
259 		storage = cgroup_storage_lookup(map, key, true);
260 		if (!storage)
261 			goto enoent;
262 
263 		storage = list_next_entry(storage, list_map);
264 		if (!storage)
265 			goto enoent;
266 	} else {
267 		storage = list_first_entry(&map->list,
268 					 struct bpf_cgroup_storage, list_map);
269 	}
270 
271 	spin_unlock_bh(&map->lock);
272 
273 	if (attach_type_isolated(&map->map)) {
274 		struct bpf_cgroup_storage_key *next = _next_key;
275 		*next = storage->key;
276 	} else {
277 		__u64 *next = _next_key;
278 		*next = storage->key.cgroup_inode_id;
279 	}
280 	return 0;
281 
282 enoent:
283 	spin_unlock_bh(&map->lock);
284 	return -ENOENT;
285 }
286 
287 static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
288 {
289 	int numa_node = bpf_map_attr_numa_node(attr);
290 	struct bpf_cgroup_storage_map *map;
291 
292 	if (attr->key_size != sizeof(struct bpf_cgroup_storage_key) &&
293 	    attr->key_size != sizeof(__u64))
294 		return ERR_PTR(-EINVAL);
295 
296 	if (attr->value_size == 0)
297 		return ERR_PTR(-EINVAL);
298 
299 	if (attr->value_size > PAGE_SIZE)
300 		return ERR_PTR(-E2BIG);
301 
302 	if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK ||
303 	    !bpf_map_flags_access_ok(attr->map_flags))
304 		return ERR_PTR(-EINVAL);
305 
306 	if (attr->max_entries)
307 		/* max_entries is not used and enforced to be 0 */
308 		return ERR_PTR(-EINVAL);
309 
310 	map = kmalloc_node(sizeof(struct bpf_cgroup_storage_map),
311 			   __GFP_ZERO | GFP_USER | __GFP_ACCOUNT, numa_node);
312 	if (!map)
313 		return ERR_PTR(-ENOMEM);
314 
315 	/* copy mandatory map attributes */
316 	bpf_map_init_from_attr(&map->map, attr);
317 
318 	spin_lock_init(&map->lock);
319 	map->root = RB_ROOT;
320 	INIT_LIST_HEAD(&map->list);
321 
322 	return &map->map;
323 }
324 
325 static void cgroup_storage_map_free(struct bpf_map *_map)
326 {
327 	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
328 	struct list_head *storages = &map->list;
329 	struct bpf_cgroup_storage *storage, *stmp;
330 
331 	mutex_lock(&cgroup_mutex);
332 
333 	list_for_each_entry_safe(storage, stmp, storages, list_map) {
334 		bpf_cgroup_storage_unlink(storage);
335 		bpf_cgroup_storage_free(storage);
336 	}
337 
338 	mutex_unlock(&cgroup_mutex);
339 
340 	WARN_ON(!RB_EMPTY_ROOT(&map->root));
341 	WARN_ON(!list_empty(&map->list));
342 
343 	kfree(map);
344 }
345 
346 static int cgroup_storage_delete_elem(struct bpf_map *map, void *key)
347 {
348 	return -EINVAL;
349 }
350 
351 static int cgroup_storage_check_btf(const struct bpf_map *map,
352 				    const struct btf *btf,
353 				    const struct btf_type *key_type,
354 				    const struct btf_type *value_type)
355 {
356 	if (attach_type_isolated(map)) {
357 		struct btf_member *m;
358 		u32 offset, size;
359 
360 		/* Key is expected to be of struct bpf_cgroup_storage_key type,
361 		 * which is:
362 		 * struct bpf_cgroup_storage_key {
363 		 *	__u64	cgroup_inode_id;
364 		 *	__u32	attach_type;
365 		 * };
366 		 */
367 
368 		/*
369 		 * Key_type must be a structure with two fields.
370 		 */
371 		if (BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ||
372 		    BTF_INFO_VLEN(key_type->info) != 2)
373 			return -EINVAL;
374 
375 		/*
376 		 * The first field must be a 64 bit integer at 0 offset.
377 		 */
378 		m = (struct btf_member *)(key_type + 1);
379 		size = sizeof_field(struct bpf_cgroup_storage_key, cgroup_inode_id);
380 		if (!btf_member_is_reg_int(btf, key_type, m, 0, size))
381 			return -EINVAL;
382 
383 		/*
384 		 * The second field must be a 32 bit integer at 64 bit offset.
385 		 */
386 		m++;
387 		offset = offsetof(struct bpf_cgroup_storage_key, attach_type);
388 		size = sizeof_field(struct bpf_cgroup_storage_key, attach_type);
389 		if (!btf_member_is_reg_int(btf, key_type, m, offset, size))
390 			return -EINVAL;
391 	} else {
392 		u32 int_data;
393 
394 		/*
395 		 * Key is expected to be u64, which stores the cgroup_inode_id
396 		 */
397 
398 		if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
399 			return -EINVAL;
400 
401 		int_data = *(u32 *)(key_type + 1);
402 		if (BTF_INT_BITS(int_data) != 64 || BTF_INT_OFFSET(int_data))
403 			return -EINVAL;
404 	}
405 
406 	return 0;
407 }
408 
409 static void cgroup_storage_seq_show_elem(struct bpf_map *map, void *key,
410 					 struct seq_file *m)
411 {
412 	enum bpf_cgroup_storage_type stype = cgroup_storage_type(map);
413 	struct bpf_cgroup_storage *storage;
414 	int cpu;
415 
416 	rcu_read_lock();
417 	storage = cgroup_storage_lookup(map_to_storage(map), key, false);
418 	if (!storage) {
419 		rcu_read_unlock();
420 		return;
421 	}
422 
423 	btf_type_seq_show(map->btf, map->btf_key_type_id, key, m);
424 	stype = cgroup_storage_type(map);
425 	if (stype == BPF_CGROUP_STORAGE_SHARED) {
426 		seq_puts(m, ": ");
427 		btf_type_seq_show(map->btf, map->btf_value_type_id,
428 				  &READ_ONCE(storage->buf)->data[0], m);
429 		seq_puts(m, "\n");
430 	} else {
431 		seq_puts(m, ": {\n");
432 		for_each_possible_cpu(cpu) {
433 			seq_printf(m, "\tcpu%d: ", cpu);
434 			btf_type_seq_show(map->btf, map->btf_value_type_id,
435 					  per_cpu_ptr(storage->percpu_buf, cpu),
436 					  m);
437 			seq_puts(m, "\n");
438 		}
439 		seq_puts(m, "}\n");
440 	}
441 	rcu_read_unlock();
442 }
443 
444 static int cgroup_storage_map_btf_id;
445 const struct bpf_map_ops cgroup_storage_map_ops = {
446 	.map_alloc = cgroup_storage_map_alloc,
447 	.map_free = cgroup_storage_map_free,
448 	.map_get_next_key = cgroup_storage_get_next_key,
449 	.map_lookup_elem = cgroup_storage_lookup_elem,
450 	.map_update_elem = cgroup_storage_update_elem,
451 	.map_delete_elem = cgroup_storage_delete_elem,
452 	.map_check_btf = cgroup_storage_check_btf,
453 	.map_seq_show_elem = cgroup_storage_seq_show_elem,
454 	.map_btf_name = "bpf_cgroup_storage_map",
455 	.map_btf_id = &cgroup_storage_map_btf_id,
456 };
457 
458 int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *_map)
459 {
460 	enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
461 
462 	if (aux->cgroup_storage[stype] &&
463 	    aux->cgroup_storage[stype] != _map)
464 		return -EBUSY;
465 
466 	aux->cgroup_storage[stype] = _map;
467 	return 0;
468 }
469 
470 static size_t bpf_cgroup_storage_calculate_size(struct bpf_map *map, u32 *pages)
471 {
472 	size_t size;
473 
474 	if (cgroup_storage_type(map) == BPF_CGROUP_STORAGE_SHARED) {
475 		size = sizeof(struct bpf_storage_buffer) + map->value_size;
476 		*pages = round_up(sizeof(struct bpf_cgroup_storage) + size,
477 				  PAGE_SIZE) >> PAGE_SHIFT;
478 	} else {
479 		size = map->value_size;
480 		*pages = round_up(round_up(size, 8) * num_possible_cpus(),
481 				  PAGE_SIZE) >> PAGE_SHIFT;
482 	}
483 
484 	return size;
485 }
486 
487 struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
488 					enum bpf_cgroup_storage_type stype)
489 {
490 	const gfp_t gfp = __GFP_ZERO | GFP_USER;
491 	struct bpf_cgroup_storage *storage;
492 	struct bpf_map *map;
493 	size_t size;
494 	u32 pages;
495 
496 	map = prog->aux->cgroup_storage[stype];
497 	if (!map)
498 		return NULL;
499 
500 	size = bpf_cgroup_storage_calculate_size(map, &pages);
501 
502 	storage = bpf_map_kmalloc_node(map, sizeof(struct bpf_cgroup_storage),
503 				       gfp, map->numa_node);
504 	if (!storage)
505 		goto enomem;
506 
507 	if (stype == BPF_CGROUP_STORAGE_SHARED) {
508 		storage->buf = bpf_map_kmalloc_node(map, size, gfp,
509 						    map->numa_node);
510 		if (!storage->buf)
511 			goto enomem;
512 		check_and_init_map_lock(map, storage->buf->data);
513 	} else {
514 		storage->percpu_buf = bpf_map_alloc_percpu(map, size, 8, gfp);
515 		if (!storage->percpu_buf)
516 			goto enomem;
517 	}
518 
519 	storage->map = (struct bpf_cgroup_storage_map *)map;
520 
521 	return storage;
522 
523 enomem:
524 	kfree(storage);
525 	return ERR_PTR(-ENOMEM);
526 }
527 
528 static void free_shared_cgroup_storage_rcu(struct rcu_head *rcu)
529 {
530 	struct bpf_cgroup_storage *storage =
531 		container_of(rcu, struct bpf_cgroup_storage, rcu);
532 
533 	kfree(storage->buf);
534 	kfree(storage);
535 }
536 
537 static void free_percpu_cgroup_storage_rcu(struct rcu_head *rcu)
538 {
539 	struct bpf_cgroup_storage *storage =
540 		container_of(rcu, struct bpf_cgroup_storage, rcu);
541 
542 	free_percpu(storage->percpu_buf);
543 	kfree(storage);
544 }
545 
546 void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
547 {
548 	enum bpf_cgroup_storage_type stype;
549 	struct bpf_map *map;
550 
551 	if (!storage)
552 		return;
553 
554 	map = &storage->map->map;
555 	stype = cgroup_storage_type(map);
556 	if (stype == BPF_CGROUP_STORAGE_SHARED)
557 		call_rcu(&storage->rcu, free_shared_cgroup_storage_rcu);
558 	else
559 		call_rcu(&storage->rcu, free_percpu_cgroup_storage_rcu);
560 }
561 
562 void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
563 			     struct cgroup *cgroup,
564 			     enum bpf_attach_type type)
565 {
566 	struct bpf_cgroup_storage_map *map;
567 
568 	if (!storage)
569 		return;
570 
571 	storage->key.attach_type = type;
572 	storage->key.cgroup_inode_id = cgroup_id(cgroup);
573 
574 	map = storage->map;
575 
576 	spin_lock_bh(&map->lock);
577 	WARN_ON(cgroup_storage_insert(map, storage));
578 	list_add(&storage->list_map, &map->list);
579 	list_add(&storage->list_cg, &cgroup->bpf.storages);
580 	spin_unlock_bh(&map->lock);
581 }
582 
583 void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
584 {
585 	struct bpf_cgroup_storage_map *map;
586 	struct rb_root *root;
587 
588 	if (!storage)
589 		return;
590 
591 	map = storage->map;
592 
593 	spin_lock_bh(&map->lock);
594 	root = &map->root;
595 	rb_erase(&storage->node, root);
596 
597 	list_del(&storage->list_map);
598 	list_del(&storage->list_cg);
599 	spin_unlock_bh(&map->lock);
600 }
601 
602 #endif
603