1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (c) 2020 Facebook
  4 * Copyright 2020 Google LLC.
  5 */
  6
  7#include <linux/pid.h>
  8#include <linux/sched.h>
  9#include <linux/rculist.h>
 10#include <linux/list.h>
 11#include <linux/hash.h>
 12#include <linux/types.h>
 13#include <linux/spinlock.h>
 14#include <linux/bpf.h>
 15#include <linux/bpf_local_storage.h>
 16#include <linux/filter.h>
 17#include <uapi/linux/btf.h>
 18#include <linux/btf_ids.h>
 19#include <linux/fdtable.h>
 20
 21DEFINE_BPF_STORAGE_CACHE(task_cache);
 22
 23static DEFINE_PER_CPU(int, bpf_task_storage_busy);
 24
 25static void bpf_task_storage_lock(void)
 26{
 27	migrate_disable();
 28	__this_cpu_inc(bpf_task_storage_busy);
 29}
 30
 31static void bpf_task_storage_unlock(void)
 32{
 33	__this_cpu_dec(bpf_task_storage_busy);
 34	migrate_enable();
 35}
 36
 37static bool bpf_task_storage_trylock(void)
 38{
 39	migrate_disable();
 40	if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
 41		__this_cpu_dec(bpf_task_storage_busy);
 42		migrate_enable();
 43		return false;
 44	}
 45	return true;
 46}
 47
 48static struct bpf_local_storage __rcu **task_storage_ptr(void *owner)
 49{
 50	struct task_struct *task = owner;
 51
 52	return &task->bpf_storage;
 53}
 54
 55static struct bpf_local_storage_data *
 56task_storage_lookup(struct task_struct *task, struct bpf_map *map,
 57		    bool cacheit_lockit)
 58{
 59	struct bpf_local_storage *task_storage;
 60	struct bpf_local_storage_map *smap;
 61
 62	task_storage = rcu_dereference(task->bpf_storage);
 63	if (!task_storage)
 64		return NULL;
 65
 66	smap = (struct bpf_local_storage_map *)map;
 67	return bpf_local_storage_lookup(task_storage, smap, cacheit_lockit);
 68}
 69
 70void bpf_task_storage_free(struct task_struct *task)
 71{
 72	struct bpf_local_storage_elem *selem;
 73	struct bpf_local_storage *local_storage;
 74	bool free_task_storage = false;
 75	struct hlist_node *n;
 76	unsigned long flags;
 77
 78	rcu_read_lock();
 79
 80	local_storage = rcu_dereference(task->bpf_storage);
 81	if (!local_storage) {
 82		rcu_read_unlock();
 83		return;
 84	}
 85
 86	/* Neither the bpf_prog nor the bpf-map's syscall
 87	 * could be modifying the local_storage->list now.
 88	 * Thus, no elem can be added-to or deleted-from the
 89	 * local_storage->list by the bpf_prog or by the bpf-map's syscall.
 90	 *
 91	 * It is racing with bpf_local_storage_map_free() alone
 92	 * when unlinking elem from the local_storage->list and
 93	 * the map's bucket->list.
 94	 */
 95	bpf_task_storage_lock();
 96	raw_spin_lock_irqsave(&local_storage->lock, flags);
 97	hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
 98		/* Always unlink from map before unlinking from
 99		 * local_storage.
100		 */
101		bpf_selem_unlink_map(selem);
102		free_task_storage = bpf_selem_unlink_storage_nolock(
103			local_storage, selem, false);
104	}
105	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
106	bpf_task_storage_unlock();
107	rcu_read_unlock();
108
109	/* free_task_storage should always be true as long as
110	 * local_storage->list was non-empty.
111	 */
112	if (free_task_storage)
113		kfree_rcu(local_storage, rcu);
114}
115
116static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
117{
118	struct bpf_local_storage_data *sdata;
119	struct task_struct *task;
120	unsigned int f_flags;
121	struct pid *pid;
122	int fd, err;
123
124	fd = *(int *)key;
125	pid = pidfd_get_pid(fd, &f_flags);
126	if (IS_ERR(pid))
127		return ERR_CAST(pid);
128
129	/* We should be in an RCU read side critical section, it should be safe
130	 * to call pid_task.
131	 */
132	WARN_ON_ONCE(!rcu_read_lock_held());
133	task = pid_task(pid, PIDTYPE_PID);
134	if (!task) {
135		err = -ENOENT;
136		goto out;
137	}
138
139	bpf_task_storage_lock();
140	sdata = task_storage_lookup(task, map, true);
141	bpf_task_storage_unlock();
142	put_pid(pid);
143	return sdata ? sdata->data : NULL;
144out:
145	put_pid(pid);
146	return ERR_PTR(err);
147}
148
149static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
150					    void *value, u64 map_flags)
151{
152	struct bpf_local_storage_data *sdata;
153	struct task_struct *task;
154	unsigned int f_flags;
155	struct pid *pid;
156	int fd, err;
157
158	fd = *(int *)key;
159	pid = pidfd_get_pid(fd, &f_flags);
160	if (IS_ERR(pid))
161		return PTR_ERR(pid);
162
163	/* We should be in an RCU read side critical section, it should be safe
164	 * to call pid_task.
165	 */
166	WARN_ON_ONCE(!rcu_read_lock_held());
167	task = pid_task(pid, PIDTYPE_PID);
168	if (!task) {
169		err = -ENOENT;
170		goto out;
171	}
172
173	bpf_task_storage_lock();
174	sdata = bpf_local_storage_update(
175		task, (struct bpf_local_storage_map *)map, value, map_flags);
176	bpf_task_storage_unlock();
177
178	err = PTR_ERR_OR_ZERO(sdata);
179out:
180	put_pid(pid);
181	return err;
182}
183
184static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
185{
186	struct bpf_local_storage_data *sdata;
187
188	sdata = task_storage_lookup(task, map, false);
189	if (!sdata)
190		return -ENOENT;
191
192	bpf_selem_unlink(SELEM(sdata));
193
194	return 0;
195}
196
197static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
198{
199	struct task_struct *task;
200	unsigned int f_flags;
201	struct pid *pid;
202	int fd, err;
203
204	fd = *(int *)key;
205	pid = pidfd_get_pid(fd, &f_flags);
206	if (IS_ERR(pid))
207		return PTR_ERR(pid);
208
209	/* We should be in an RCU read side critical section, it should be safe
210	 * to call pid_task.
211	 */
212	WARN_ON_ONCE(!rcu_read_lock_held());
213	task = pid_task(pid, PIDTYPE_PID);
214	if (!task) {
215		err = -ENOENT;
216		goto out;
217	}
218
219	bpf_task_storage_lock();
220	err = task_storage_delete(task, map);
221	bpf_task_storage_unlock();
222out:
223	put_pid(pid);
224	return err;
225}
226
227BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
228	   task, void *, value, u64, flags)
229{
230	struct bpf_local_storage_data *sdata;
231
232	if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
233		return (unsigned long)NULL;
234
235	if (!task)
236		return (unsigned long)NULL;
237
238	if (!bpf_task_storage_trylock())
239		return (unsigned long)NULL;
240
241	sdata = task_storage_lookup(task, map, true);
242	if (sdata)
243		goto unlock;
244
245	/* only allocate new storage, when the task is refcounted */
246	if (refcount_read(&task->usage) &&
247	    (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
248		sdata = bpf_local_storage_update(
249			task, (struct bpf_local_storage_map *)map, value,
250			BPF_NOEXIST);
251
252unlock:
253	bpf_task_storage_unlock();
254	return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL :
255		(unsigned long)sdata->data;
256}
257
258BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *,
259	   task)
260{
261	int ret;
262
263	if (!task)
264		return -EINVAL;
265
266	if (!bpf_task_storage_trylock())
267		return -EBUSY;
268
269	/* This helper must only be called from places where the lifetime of the task
270	 * is guaranteed. Either by being refcounted or by being protected
271	 * by an RCU read-side critical section.
272	 */
273	ret = task_storage_delete(task, map);
274	bpf_task_storage_unlock();
275	return ret;
276}
277
278static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)
279{
280	return -ENOTSUPP;
281}
282
283static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr)
284{
285	struct bpf_local_storage_map *smap;
286
287	smap = bpf_local_storage_map_alloc(attr);
288	if (IS_ERR(smap))
289		return ERR_CAST(smap);
290
291	smap->cache_idx = bpf_local_storage_cache_idx_get(&task_cache);
292	return &smap->map;
293}
294
295static void task_storage_map_free(struct bpf_map *map)
296{
297	struct bpf_local_storage_map *smap;
298
299	smap = (struct bpf_local_storage_map *)map;
300	bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx);
301	bpf_local_storage_map_free(smap, &bpf_task_storage_busy);
302}
303
304static int task_storage_map_btf_id;
305const struct bpf_map_ops task_storage_map_ops = {
306	.map_meta_equal = bpf_map_meta_equal,
307	.map_alloc_check = bpf_local_storage_map_alloc_check,
308	.map_alloc = task_storage_map_alloc,
309	.map_free = task_storage_map_free,
310	.map_get_next_key = notsupp_get_next_key,
311	.map_lookup_elem = bpf_pid_task_storage_lookup_elem,
312	.map_update_elem = bpf_pid_task_storage_update_elem,
313	.map_delete_elem = bpf_pid_task_storage_delete_elem,
314	.map_check_btf = bpf_local_storage_map_check_btf,
315	.map_btf_name = "bpf_local_storage_map",
316	.map_btf_id = &task_storage_map_btf_id,
317	.map_owner_storage_ptr = task_storage_ptr,
318};
319
320BTF_ID_LIST_SINGLE(bpf_task_storage_btf_ids, struct, task_struct)
321
322const struct bpf_func_proto bpf_task_storage_get_proto = {
323	.func = bpf_task_storage_get,
324	.gpl_only = false,
325	.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
326	.arg1_type = ARG_CONST_MAP_PTR,
327	.arg2_type = ARG_PTR_TO_BTF_ID,
328	.arg2_btf_id = &bpf_task_storage_btf_ids[0],
329	.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
330	.arg4_type = ARG_ANYTHING,
331};
332
333const struct bpf_func_proto bpf_task_storage_delete_proto = {
334	.func = bpf_task_storage_delete,
335	.gpl_only = false,
336	.ret_type = RET_INTEGER,
337	.arg1_type = ARG_CONST_MAP_PTR,
338	.arg2_type = ARG_PTR_TO_BTF_ID,
339	.arg2_btf_id = &bpf_task_storage_btf_ids[0],
340};