1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2019 Facebook  */
3 #include <linux/rculist.h>
4 #include <linux/list.h>
5 #include <linux/hash.h>
6 #include <linux/types.h>
7 #include <linux/spinlock.h>
8 #include <linux/bpf.h>
9 #include <linux/btf_ids.h>
10 #include <linux/bpf_local_storage.h>
11 #include <net/sock.h>
12 #include <uapi/linux/sock_diag.h>
13 #include <uapi/linux/btf.h>
14 #include <linux/rcupdate.h>
15 #include <linux/rcupdate_trace.h>
16 #include <linux/rcupdate_wait.h>
17 
18 #define BPF_LOCAL_STORAGE_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_CLONE)
19 
20 static struct bpf_local_storage_map_bucket *
select_bucket(struct bpf_local_storage_map * smap,struct bpf_local_storage_elem * selem)21 select_bucket(struct bpf_local_storage_map *smap,
22 	      struct bpf_local_storage_elem *selem)
23 {
24 	return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
25 }
26 
mem_charge(struct bpf_local_storage_map * smap,void * owner,u32 size)27 static int mem_charge(struct bpf_local_storage_map *smap, void *owner, u32 size)
28 {
29 	struct bpf_map *map = &smap->map;
30 
31 	if (!map->ops->map_local_storage_charge)
32 		return 0;
33 
34 	return map->ops->map_local_storage_charge(smap, owner, size);
35 }
36 
mem_uncharge(struct bpf_local_storage_map * smap,void * owner,u32 size)37 static void mem_uncharge(struct bpf_local_storage_map *smap, void *owner,
38 			 u32 size)
39 {
40 	struct bpf_map *map = &smap->map;
41 
42 	if (map->ops->map_local_storage_uncharge)
43 		map->ops->map_local_storage_uncharge(smap, owner, size);
44 }
45 
46 static struct bpf_local_storage __rcu **
owner_storage(struct bpf_local_storage_map * smap,void * owner)47 owner_storage(struct bpf_local_storage_map *smap, void *owner)
48 {
49 	struct bpf_map *map = &smap->map;
50 
51 	return map->ops->map_owner_storage_ptr(owner);
52 }
53 
selem_linked_to_storage(const struct bpf_local_storage_elem * selem)54 static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
55 {
56 	return !hlist_unhashed(&selem->snode);
57 }
58 
selem_linked_to_map(const struct bpf_local_storage_elem * selem)59 static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem)
60 {
61 	return !hlist_unhashed(&selem->map_node);
62 }
63 
64 struct bpf_local_storage_elem *
bpf_selem_alloc(struct bpf_local_storage_map * smap,void * owner,void * value,bool charge_mem,gfp_t gfp_flags)65 bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
66 		void *value, bool charge_mem, gfp_t gfp_flags)
67 {
68 	struct bpf_local_storage_elem *selem;
69 
70 	if (charge_mem && mem_charge(smap, owner, smap->elem_size))
71 		return NULL;
72 
73 	selem = bpf_map_kzalloc(&smap->map, smap->elem_size,
74 				gfp_flags | __GFP_NOWARN);
75 	if (selem) {
76 		if (value)
77 			copy_map_value(&smap->map, SDATA(selem)->data, value);
78 		return selem;
79 	}
80 
81 	if (charge_mem)
82 		mem_uncharge(smap, owner, smap->elem_size);
83 
84 	return NULL;
85 }
86 
bpf_local_storage_free_rcu(struct rcu_head * rcu)87 void bpf_local_storage_free_rcu(struct rcu_head *rcu)
88 {
89 	struct bpf_local_storage *local_storage;
90 
91 	local_storage = container_of(rcu, struct bpf_local_storage, rcu);
92 	kfree_rcu(local_storage, rcu);
93 }
94 
bpf_selem_free_rcu(struct rcu_head * rcu)95 static void bpf_selem_free_rcu(struct rcu_head *rcu)
96 {
97 	struct bpf_local_storage_elem *selem;
98 
99 	selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
100 	kfree_rcu(selem, rcu);
101 }
102 
103 /* local_storage->lock must be held and selem->local_storage == local_storage.
104  * The caller must ensure selem->smap is still valid to be
105  * dereferenced for its smap->elem_size and smap->cache_idx.
106  */
bpf_selem_unlink_storage_nolock(struct bpf_local_storage * local_storage,struct bpf_local_storage_elem * selem,bool uncharge_mem,bool use_trace_rcu)107 bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
108 				     struct bpf_local_storage_elem *selem,
109 				     bool uncharge_mem, bool use_trace_rcu)
110 {
111 	struct bpf_local_storage_map *smap;
112 	bool free_local_storage;
113 	void *owner;
114 
115 	smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
116 	owner = local_storage->owner;
117 
118 	/* All uncharging on the owner must be done first.
119 	 * The owner may be freed once the last selem is unlinked
120 	 * from local_storage.
121 	 */
122 	if (uncharge_mem)
123 		mem_uncharge(smap, owner, smap->elem_size);
124 
125 	free_local_storage = hlist_is_singular_node(&selem->snode,
126 						    &local_storage->list);
127 	if (free_local_storage) {
128 		mem_uncharge(smap, owner, sizeof(struct bpf_local_storage));
129 		local_storage->owner = NULL;
130 
131 		/* After this RCU_INIT, owner may be freed and cannot be used */
132 		RCU_INIT_POINTER(*owner_storage(smap, owner), NULL);
133 
134 		/* local_storage is not freed now.  local_storage->lock is
135 		 * still held and raw_spin_unlock_bh(&local_storage->lock)
136 		 * will be done by the caller.
137 		 *
138 		 * Although the unlock will be done under
139 		 * rcu_read_lock(),  it is more intuitive to
140 		 * read if the freeing of the storage is done
141 		 * after the raw_spin_unlock_bh(&local_storage->lock).
142 		 *
143 		 * Hence, a "bool free_local_storage" is returned
144 		 * to the caller which then calls then frees the storage after
145 		 * all the RCU grace periods have expired.
146 		 */
147 	}
148 	hlist_del_init_rcu(&selem->snode);
149 	if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) ==
150 	    SDATA(selem))
151 		RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
152 
153 	if (use_trace_rcu)
154 		call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu);
155 	else
156 		kfree_rcu(selem, rcu);
157 
158 	return free_local_storage;
159 }
160 
__bpf_selem_unlink_storage(struct bpf_local_storage_elem * selem,bool use_trace_rcu)161 static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
162 				       bool use_trace_rcu)
163 {
164 	struct bpf_local_storage *local_storage;
165 	bool free_local_storage = false;
166 	unsigned long flags;
167 
168 	if (unlikely(!selem_linked_to_storage(selem)))
169 		/* selem has already been unlinked from sk */
170 		return;
171 
172 	local_storage = rcu_dereference_check(selem->local_storage,
173 					      bpf_rcu_lock_held());
174 	raw_spin_lock_irqsave(&local_storage->lock, flags);
175 	if (likely(selem_linked_to_storage(selem)))
176 		free_local_storage = bpf_selem_unlink_storage_nolock(
177 			local_storage, selem, true, use_trace_rcu);
178 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
179 
180 	if (free_local_storage) {
181 		if (use_trace_rcu)
182 			call_rcu_tasks_trace(&local_storage->rcu,
183 				     bpf_local_storage_free_rcu);
184 		else
185 			kfree_rcu(local_storage, rcu);
186 	}
187 }
188 
bpf_selem_link_storage_nolock(struct bpf_local_storage * local_storage,struct bpf_local_storage_elem * selem)189 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
190 				   struct bpf_local_storage_elem *selem)
191 {
192 	RCU_INIT_POINTER(selem->local_storage, local_storage);
193 	hlist_add_head_rcu(&selem->snode, &local_storage->list);
194 }
195 
bpf_selem_unlink_map(struct bpf_local_storage_elem * selem)196 void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
197 {
198 	struct bpf_local_storage_map *smap;
199 	struct bpf_local_storage_map_bucket *b;
200 	unsigned long flags;
201 
202 	if (unlikely(!selem_linked_to_map(selem)))
203 		/* selem has already be unlinked from smap */
204 		return;
205 
206 	smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
207 	b = select_bucket(smap, selem);
208 	raw_spin_lock_irqsave(&b->lock, flags);
209 	if (likely(selem_linked_to_map(selem)))
210 		hlist_del_init_rcu(&selem->map_node);
211 	raw_spin_unlock_irqrestore(&b->lock, flags);
212 }
213 
bpf_selem_link_map(struct bpf_local_storage_map * smap,struct bpf_local_storage_elem * selem)214 void bpf_selem_link_map(struct bpf_local_storage_map *smap,
215 			struct bpf_local_storage_elem *selem)
216 {
217 	struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
218 	unsigned long flags;
219 
220 	raw_spin_lock_irqsave(&b->lock, flags);
221 	RCU_INIT_POINTER(SDATA(selem)->smap, smap);
222 	hlist_add_head_rcu(&selem->map_node, &b->list);
223 	raw_spin_unlock_irqrestore(&b->lock, flags);
224 }
225 
bpf_selem_unlink(struct bpf_local_storage_elem * selem,bool use_trace_rcu)226 void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu)
227 {
228 	/* Always unlink from map before unlinking from local_storage
229 	 * because selem will be freed after successfully unlinked from
230 	 * the local_storage.
231 	 */
232 	bpf_selem_unlink_map(selem);
233 	__bpf_selem_unlink_storage(selem, use_trace_rcu);
234 }
235 
236 struct bpf_local_storage_data *
bpf_local_storage_lookup(struct bpf_local_storage * local_storage,struct bpf_local_storage_map * smap,bool cacheit_lockit)237 bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
238 			 struct bpf_local_storage_map *smap,
239 			 bool cacheit_lockit)
240 {
241 	struct bpf_local_storage_data *sdata;
242 	struct bpf_local_storage_elem *selem;
243 
244 	/* Fast path (cache hit) */
245 	sdata = rcu_dereference_check(local_storage->cache[smap->cache_idx],
246 				      bpf_rcu_lock_held());
247 	if (sdata && rcu_access_pointer(sdata->smap) == smap)
248 		return sdata;
249 
250 	/* Slow path (cache miss) */
251 	hlist_for_each_entry_rcu(selem, &local_storage->list, snode,
252 				  rcu_read_lock_trace_held())
253 		if (rcu_access_pointer(SDATA(selem)->smap) == smap)
254 			break;
255 
256 	if (!selem)
257 		return NULL;
258 
259 	sdata = SDATA(selem);
260 	if (cacheit_lockit) {
261 		unsigned long flags;
262 
263 		/* spinlock is needed to avoid racing with the
264 		 * parallel delete.  Otherwise, publishing an already
265 		 * deleted sdata to the cache will become a use-after-free
266 		 * problem in the next bpf_local_storage_lookup().
267 		 */
268 		raw_spin_lock_irqsave(&local_storage->lock, flags);
269 		if (selem_linked_to_storage(selem))
270 			rcu_assign_pointer(local_storage->cache[smap->cache_idx],
271 					   sdata);
272 		raw_spin_unlock_irqrestore(&local_storage->lock, flags);
273 	}
274 
275 	return sdata;
276 }
277 
check_flags(const struct bpf_local_storage_data * old_sdata,u64 map_flags)278 static int check_flags(const struct bpf_local_storage_data *old_sdata,
279 		       u64 map_flags)
280 {
281 	if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
282 		/* elem already exists */
283 		return -EEXIST;
284 
285 	if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
286 		/* elem doesn't exist, cannot update it */
287 		return -ENOENT;
288 
289 	return 0;
290 }
291 
bpf_local_storage_alloc(void * owner,struct bpf_local_storage_map * smap,struct bpf_local_storage_elem * first_selem,gfp_t gfp_flags)292 int bpf_local_storage_alloc(void *owner,
293 			    struct bpf_local_storage_map *smap,
294 			    struct bpf_local_storage_elem *first_selem,
295 			    gfp_t gfp_flags)
296 {
297 	struct bpf_local_storage *prev_storage, *storage;
298 	struct bpf_local_storage **owner_storage_ptr;
299 	int err;
300 
301 	err = mem_charge(smap, owner, sizeof(*storage));
302 	if (err)
303 		return err;
304 
305 	storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
306 				  gfp_flags | __GFP_NOWARN);
307 	if (!storage) {
308 		err = -ENOMEM;
309 		goto uncharge;
310 	}
311 
312 	INIT_HLIST_HEAD(&storage->list);
313 	raw_spin_lock_init(&storage->lock);
314 	storage->owner = owner;
315 
316 	bpf_selem_link_storage_nolock(storage, first_selem);
317 	bpf_selem_link_map(smap, first_selem);
318 
319 	owner_storage_ptr =
320 		(struct bpf_local_storage **)owner_storage(smap, owner);
321 	/* Publish storage to the owner.
322 	 * Instead of using any lock of the kernel object (i.e. owner),
323 	 * cmpxchg will work with any kernel object regardless what
324 	 * the running context is, bh, irq...etc.
325 	 *
326 	 * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage)
327 	 * is protected by the storage->lock.  Hence, when freeing
328 	 * the owner->storage, the storage->lock must be held before
329 	 * setting owner->storage ptr to NULL.
330 	 */
331 	prev_storage = cmpxchg(owner_storage_ptr, NULL, storage);
332 	if (unlikely(prev_storage)) {
333 		bpf_selem_unlink_map(first_selem);
334 		err = -EAGAIN;
335 		goto uncharge;
336 
337 		/* Note that even first_selem was linked to smap's
338 		 * bucket->list, first_selem can be freed immediately
339 		 * (instead of kfree_rcu) because
340 		 * bpf_local_storage_map_free() does a
341 		 * synchronize_rcu_mult (waiting for both sleepable and
342 		 * normal programs) before walking the bucket->list.
343 		 * Hence, no one is accessing selem from the
344 		 * bucket->list under rcu_read_lock().
345 		 */
346 	}
347 
348 	return 0;
349 
350 uncharge:
351 	kfree(storage);
352 	mem_uncharge(smap, owner, sizeof(*storage));
353 	return err;
354 }
355 
356 /* sk cannot be going away because it is linking new elem
357  * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0).
358  * Otherwise, it will become a leak (and other memory issues
359  * during map destruction).
360  */
361 struct bpf_local_storage_data *
bpf_local_storage_update(void * owner,struct bpf_local_storage_map * smap,void * value,u64 map_flags,gfp_t gfp_flags)362 bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
363 			 void *value, u64 map_flags, gfp_t gfp_flags)
364 {
365 	struct bpf_local_storage_data *old_sdata = NULL;
366 	struct bpf_local_storage_elem *selem = NULL;
367 	struct bpf_local_storage *local_storage;
368 	unsigned long flags;
369 	int err;
370 
371 	/* BPF_EXIST and BPF_NOEXIST cannot be both set */
372 	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
373 	    /* BPF_F_LOCK can only be used in a value with spin_lock */
374 	    unlikely((map_flags & BPF_F_LOCK) &&
375 		     !map_value_has_spin_lock(&smap->map)))
376 		return ERR_PTR(-EINVAL);
377 
378 	if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST)
379 		return ERR_PTR(-EINVAL);
380 
381 	local_storage = rcu_dereference_check(*owner_storage(smap, owner),
382 					      bpf_rcu_lock_held());
383 	if (!local_storage || hlist_empty(&local_storage->list)) {
384 		/* Very first elem for the owner */
385 		err = check_flags(NULL, map_flags);
386 		if (err)
387 			return ERR_PTR(err);
388 
389 		selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags);
390 		if (!selem)
391 			return ERR_PTR(-ENOMEM);
392 
393 		err = bpf_local_storage_alloc(owner, smap, selem, gfp_flags);
394 		if (err) {
395 			kfree(selem);
396 			mem_uncharge(smap, owner, smap->elem_size);
397 			return ERR_PTR(err);
398 		}
399 
400 		return SDATA(selem);
401 	}
402 
403 	if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) {
404 		/* Hoping to find an old_sdata to do inline update
405 		 * such that it can avoid taking the local_storage->lock
406 		 * and changing the lists.
407 		 */
408 		old_sdata =
409 			bpf_local_storage_lookup(local_storage, smap, false);
410 		err = check_flags(old_sdata, map_flags);
411 		if (err)
412 			return ERR_PTR(err);
413 		if (old_sdata && selem_linked_to_storage(SELEM(old_sdata))) {
414 			copy_map_value_locked(&smap->map, old_sdata->data,
415 					      value, false);
416 			return old_sdata;
417 		}
418 	}
419 
420 	if (gfp_flags == GFP_KERNEL) {
421 		selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags);
422 		if (!selem)
423 			return ERR_PTR(-ENOMEM);
424 	}
425 
426 	raw_spin_lock_irqsave(&local_storage->lock, flags);
427 
428 	/* Recheck local_storage->list under local_storage->lock */
429 	if (unlikely(hlist_empty(&local_storage->list))) {
430 		/* A parallel del is happening and local_storage is going
431 		 * away.  It has just been checked before, so very
432 		 * unlikely.  Return instead of retry to keep things
433 		 * simple.
434 		 */
435 		err = -EAGAIN;
436 		goto unlock_err;
437 	}
438 
439 	old_sdata = bpf_local_storage_lookup(local_storage, smap, false);
440 	err = check_flags(old_sdata, map_flags);
441 	if (err)
442 		goto unlock_err;
443 
444 	if (old_sdata && (map_flags & BPF_F_LOCK)) {
445 		copy_map_value_locked(&smap->map, old_sdata->data, value,
446 				      false);
447 		selem = SELEM(old_sdata);
448 		goto unlock;
449 	}
450 
451 	if (gfp_flags != GFP_KERNEL) {
452 		/* local_storage->lock is held.  Hence, we are sure
453 		 * we can unlink and uncharge the old_sdata successfully
454 		 * later.  Hence, instead of charging the new selem now
455 		 * and then uncharge the old selem later (which may cause
456 		 * a potential but unnecessary charge failure),  avoid taking
457 		 * a charge at all here (the "!old_sdata" check) and the
458 		 * old_sdata will not be uncharged later during
459 		 * bpf_selem_unlink_storage_nolock().
460 		 */
461 		selem = bpf_selem_alloc(smap, owner, value, !old_sdata, gfp_flags);
462 		if (!selem) {
463 			err = -ENOMEM;
464 			goto unlock_err;
465 		}
466 	}
467 
468 	/* First, link the new selem to the map */
469 	bpf_selem_link_map(smap, selem);
470 
471 	/* Second, link (and publish) the new selem to local_storage */
472 	bpf_selem_link_storage_nolock(local_storage, selem);
473 
474 	/* Third, remove old selem, SELEM(old_sdata) */
475 	if (old_sdata) {
476 		bpf_selem_unlink_map(SELEM(old_sdata));
477 		bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata),
478 						false, true);
479 	}
480 
481 unlock:
482 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
483 	return SDATA(selem);
484 
485 unlock_err:
486 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
487 	if (selem) {
488 		mem_uncharge(smap, owner, smap->elem_size);
489 		kfree(selem);
490 	}
491 	return ERR_PTR(err);
492 }
493 
bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache * cache)494 u16 bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache *cache)
495 {
496 	u64 min_usage = U64_MAX;
497 	u16 i, res = 0;
498 
499 	spin_lock(&cache->idx_lock);
500 
501 	for (i = 0; i < BPF_LOCAL_STORAGE_CACHE_SIZE; i++) {
502 		if (cache->idx_usage_counts[i] < min_usage) {
503 			min_usage = cache->idx_usage_counts[i];
504 			res = i;
505 
506 			/* Found a free cache_idx */
507 			if (!min_usage)
508 				break;
509 		}
510 	}
511 	cache->idx_usage_counts[res]++;
512 
513 	spin_unlock(&cache->idx_lock);
514 
515 	return res;
516 }
517 
bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache * cache,u16 idx)518 void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache,
519 				      u16 idx)
520 {
521 	spin_lock(&cache->idx_lock);
522 	cache->idx_usage_counts[idx]--;
523 	spin_unlock(&cache->idx_lock);
524 }
525 
bpf_local_storage_map_free(struct bpf_local_storage_map * smap,int __percpu * busy_counter)526 void bpf_local_storage_map_free(struct bpf_local_storage_map *smap,
527 				int __percpu *busy_counter)
528 {
529 	struct bpf_local_storage_elem *selem;
530 	struct bpf_local_storage_map_bucket *b;
531 	unsigned int i;
532 
533 	/* Note that this map might be concurrently cloned from
534 	 * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
535 	 * RCU read section to finish before proceeding. New RCU
536 	 * read sections should be prevented via bpf_map_inc_not_zero.
537 	 */
538 	synchronize_rcu();
539 
540 	/* bpf prog and the userspace can no longer access this map
541 	 * now.  No new selem (of this map) can be added
542 	 * to the owner->storage or to the map bucket's list.
543 	 *
544 	 * The elem of this map can be cleaned up here
545 	 * or when the storage is freed e.g.
546 	 * by bpf_sk_storage_free() during __sk_destruct().
547 	 */
548 	for (i = 0; i < (1U << smap->bucket_log); i++) {
549 		b = &smap->buckets[i];
550 
551 		rcu_read_lock();
552 		/* No one is adding to b->list now */
553 		while ((selem = hlist_entry_safe(
554 				rcu_dereference_raw(hlist_first_rcu(&b->list)),
555 				struct bpf_local_storage_elem, map_node))) {
556 			if (busy_counter) {
557 				migrate_disable();
558 				this_cpu_inc(*busy_counter);
559 			}
560 			bpf_selem_unlink(selem, false);
561 			if (busy_counter) {
562 				this_cpu_dec(*busy_counter);
563 				migrate_enable();
564 			}
565 			cond_resched_rcu();
566 		}
567 		rcu_read_unlock();
568 	}
569 
570 	/* While freeing the storage we may still need to access the map.
571 	 *
572 	 * e.g. when bpf_sk_storage_free() has unlinked selem from the map
573 	 * which then made the above while((selem = ...)) loop
574 	 * exit immediately.
575 	 *
576 	 * However, while freeing the storage one still needs to access the
577 	 * smap->elem_size to do the uncharging in
578 	 * bpf_selem_unlink_storage_nolock().
579 	 *
580 	 * Hence, wait another rcu grace period for the storage to be freed.
581 	 */
582 	synchronize_rcu();
583 
584 	kvfree(smap->buckets);
585 	bpf_map_area_free(smap);
586 }
587 
bpf_local_storage_map_alloc_check(union bpf_attr * attr)588 int bpf_local_storage_map_alloc_check(union bpf_attr *attr)
589 {
590 	if (attr->map_flags & ~BPF_LOCAL_STORAGE_CREATE_FLAG_MASK ||
591 	    !(attr->map_flags & BPF_F_NO_PREALLOC) ||
592 	    attr->max_entries ||
593 	    attr->key_size != sizeof(int) || !attr->value_size ||
594 	    /* Enforce BTF for userspace sk dumping */
595 	    !attr->btf_key_type_id || !attr->btf_value_type_id)
596 		return -EINVAL;
597 
598 	if (!bpf_capable())
599 		return -EPERM;
600 
601 	if (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE)
602 		return -E2BIG;
603 
604 	return 0;
605 }
606 
bpf_local_storage_map_alloc(union bpf_attr * attr)607 struct bpf_local_storage_map *bpf_local_storage_map_alloc(union bpf_attr *attr)
608 {
609 	struct bpf_local_storage_map *smap;
610 	unsigned int i;
611 	u32 nbuckets;
612 
613 	smap = bpf_map_area_alloc(sizeof(*smap), NUMA_NO_NODE);
614 	if (!smap)
615 		return ERR_PTR(-ENOMEM);
616 	bpf_map_init_from_attr(&smap->map, attr);
617 
618 	nbuckets = roundup_pow_of_two(num_possible_cpus());
619 	/* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */
620 	nbuckets = max_t(u32, 2, nbuckets);
621 	smap->bucket_log = ilog2(nbuckets);
622 
623 	smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets,
624 				 GFP_USER | __GFP_NOWARN | __GFP_ACCOUNT);
625 	if (!smap->buckets) {
626 		bpf_map_area_free(smap);
627 		return ERR_PTR(-ENOMEM);
628 	}
629 
630 	for (i = 0; i < nbuckets; i++) {
631 		INIT_HLIST_HEAD(&smap->buckets[i].list);
632 		raw_spin_lock_init(&smap->buckets[i].lock);
633 	}
634 
635 	smap->elem_size =
636 		sizeof(struct bpf_local_storage_elem) + attr->value_size;
637 
638 	return smap;
639 }
640 
bpf_local_storage_map_check_btf(const struct bpf_map * map,const struct btf * btf,const struct btf_type * key_type,const struct btf_type * value_type)641 int bpf_local_storage_map_check_btf(const struct bpf_map *map,
642 				    const struct btf *btf,
643 				    const struct btf_type *key_type,
644 				    const struct btf_type *value_type)
645 {
646 	u32 int_data;
647 
648 	if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
649 		return -EINVAL;
650 
651 	int_data = *(u32 *)(key_type + 1);
652 	if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
653 		return -EINVAL;
654 
655 	return 0;
656 }
657