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1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2020 Facebook */
3
4#include <linux/fs.h>
5#include <linux/anon_inodes.h>
6#include <linux/filter.h>
7#include <linux/bpf.h>
8
9struct bpf_iter_target_info {
10 struct list_head list;
11 const struct bpf_iter_reg *reg_info;
12 u32 btf_id; /* cached value */
13};
14
15struct bpf_iter_link {
16 struct bpf_link link;
17 struct bpf_iter_aux_info aux;
18 struct bpf_iter_target_info *tinfo;
19};
20
21struct bpf_iter_priv_data {
22 struct bpf_iter_target_info *tinfo;
23 const struct bpf_iter_seq_info *seq_info;
24 struct bpf_prog *prog;
25 u64 session_id;
26 u64 seq_num;
27 bool done_stop;
28 u8 target_private[] __aligned(8);
29};
30
31static struct list_head targets = LIST_HEAD_INIT(targets);
32static DEFINE_MUTEX(targets_mutex);
33
34/* protect bpf_iter_link changes */
35static DEFINE_MUTEX(link_mutex);
36
37/* incremented on every opened seq_file */
38static atomic64_t session_id;
39
40static int prepare_seq_file(struct file *file, struct bpf_iter_link *link,
41 const struct bpf_iter_seq_info *seq_info);
42
43static void bpf_iter_inc_seq_num(struct seq_file *seq)
44{
45 struct bpf_iter_priv_data *iter_priv;
46
47 iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
48 target_private);
49 iter_priv->seq_num++;
50}
51
52static void bpf_iter_dec_seq_num(struct seq_file *seq)
53{
54 struct bpf_iter_priv_data *iter_priv;
55
56 iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
57 target_private);
58 iter_priv->seq_num--;
59}
60
61static void bpf_iter_done_stop(struct seq_file *seq)
62{
63 struct bpf_iter_priv_data *iter_priv;
64
65 iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
66 target_private);
67 iter_priv->done_stop = true;
68}
69
70/* maximum visited objects before bailing out */
71#define MAX_ITER_OBJECTS 1000000
72
73/* bpf_seq_read, a customized and simpler version for bpf iterator.
74 * no_llseek is assumed for this file.
75 * The following are differences from seq_read():
76 * . fixed buffer size (PAGE_SIZE)
77 * . assuming no_llseek
78 * . stop() may call bpf program, handling potential overflow there
79 */
80static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
81 loff_t *ppos)
82{
83 struct seq_file *seq = file->private_data;
84 size_t n, offs, copied = 0;
85 int err = 0, num_objs = 0;
86 void *p;
87
88 mutex_lock(&seq->lock);
89
90 if (!seq->buf) {
91 seq->size = PAGE_SIZE;
92 seq->buf = kmalloc(seq->size, GFP_KERNEL);
93 if (!seq->buf) {
94 err = -ENOMEM;
95 goto done;
96 }
97 }
98
99 if (seq->count) {
100 n = min(seq->count, size);
101 err = copy_to_user(buf, seq->buf + seq->from, n);
102 if (err) {
103 err = -EFAULT;
104 goto done;
105 }
106 seq->count -= n;
107 seq->from += n;
108 copied = n;
109 goto done;
110 }
111
112 seq->from = 0;
113 p = seq->op->start(seq, &seq->index);
114 if (!p)
115 goto stop;
116 if (IS_ERR(p)) {
117 err = PTR_ERR(p);
118 seq->op->stop(seq, p);
119 seq->count = 0;
120 goto done;
121 }
122
123 err = seq->op->show(seq, p);
124 if (err > 0) {
125 /* object is skipped, decrease seq_num, so next
126 * valid object can reuse the same seq_num.
127 */
128 bpf_iter_dec_seq_num(seq);
129 seq->count = 0;
130 } else if (err < 0 || seq_has_overflowed(seq)) {
131 if (!err)
132 err = -E2BIG;
133 seq->op->stop(seq, p);
134 seq->count = 0;
135 goto done;
136 }
137
138 while (1) {
139 loff_t pos = seq->index;
140
141 num_objs++;
142 offs = seq->count;
143 p = seq->op->next(seq, p, &seq->index);
144 if (pos == seq->index) {
145 pr_info_ratelimited("buggy seq_file .next function %ps "
146 "did not updated position index\n",
147 seq->op->next);
148 seq->index++;
149 }
150
151 if (IS_ERR_OR_NULL(p))
152 break;
153
154 /* got a valid next object, increase seq_num */
155 bpf_iter_inc_seq_num(seq);
156
157 if (seq->count >= size)
158 break;
159
160 if (num_objs >= MAX_ITER_OBJECTS) {
161 if (offs == 0) {
162 err = -EAGAIN;
163 seq->op->stop(seq, p);
164 goto done;
165 }
166 break;
167 }
168
169 err = seq->op->show(seq, p);
170 if (err > 0) {
171 bpf_iter_dec_seq_num(seq);
172 seq->count = offs;
173 } else if (err < 0 || seq_has_overflowed(seq)) {
174 seq->count = offs;
175 if (offs == 0) {
176 if (!err)
177 err = -E2BIG;
178 seq->op->stop(seq, p);
179 goto done;
180 }
181 break;
182 }
183 }
184stop:
185 offs = seq->count;
186 /* bpf program called if !p */
187 seq->op->stop(seq, p);
188 if (!p) {
189 if (!seq_has_overflowed(seq)) {
190 bpf_iter_done_stop(seq);
191 } else {
192 seq->count = offs;
193 if (offs == 0) {
194 err = -E2BIG;
195 goto done;
196 }
197 }
198 }
199
200 n = min(seq->count, size);
201 err = copy_to_user(buf, seq->buf, n);
202 if (err) {
203 err = -EFAULT;
204 goto done;
205 }
206 copied = n;
207 seq->count -= n;
208 seq->from = n;
209done:
210 if (!copied)
211 copied = err;
212 else
213 *ppos += copied;
214 mutex_unlock(&seq->lock);
215 return copied;
216}
217
218static const struct bpf_iter_seq_info *
219__get_seq_info(struct bpf_iter_link *link)
220{
221 const struct bpf_iter_seq_info *seq_info;
222
223 if (link->aux.map) {
224 seq_info = link->aux.map->ops->iter_seq_info;
225 if (seq_info)
226 return seq_info;
227 }
228
229 return link->tinfo->reg_info->seq_info;
230}
231
232static int iter_open(struct inode *inode, struct file *file)
233{
234 struct bpf_iter_link *link = inode->i_private;
235
236 return prepare_seq_file(file, link, __get_seq_info(link));
237}
238
239static int iter_release(struct inode *inode, struct file *file)
240{
241 struct bpf_iter_priv_data *iter_priv;
242 struct seq_file *seq;
243
244 seq = file->private_data;
245 if (!seq)
246 return 0;
247
248 iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
249 target_private);
250
251 if (iter_priv->seq_info->fini_seq_private)
252 iter_priv->seq_info->fini_seq_private(seq->private);
253
254 bpf_prog_put(iter_priv->prog);
255 seq->private = iter_priv;
256
257 return seq_release_private(inode, file);
258}
259
260const struct file_operations bpf_iter_fops = {
261 .open = iter_open,
262 .llseek = no_llseek,
263 .read = bpf_seq_read,
264 .release = iter_release,
265};
266
267/* The argument reg_info will be cached in bpf_iter_target_info.
268 * The common practice is to declare target reg_info as
269 * a const static variable and passed as an argument to
270 * bpf_iter_reg_target().
271 */
272int bpf_iter_reg_target(const struct bpf_iter_reg *reg_info)
273{
274 struct bpf_iter_target_info *tinfo;
275
276 tinfo = kmalloc(sizeof(*tinfo), GFP_KERNEL);
277 if (!tinfo)
278 return -ENOMEM;
279
280 tinfo->reg_info = reg_info;
281 INIT_LIST_HEAD(&tinfo->list);
282
283 mutex_lock(&targets_mutex);
284 list_add(&tinfo->list, &targets);
285 mutex_unlock(&targets_mutex);
286
287 return 0;
288}
289
290void bpf_iter_unreg_target(const struct bpf_iter_reg *reg_info)
291{
292 struct bpf_iter_target_info *tinfo;
293 bool found = false;
294
295 mutex_lock(&targets_mutex);
296 list_for_each_entry(tinfo, &targets, list) {
297 if (reg_info == tinfo->reg_info) {
298 list_del(&tinfo->list);
299 kfree(tinfo);
300 found = true;
301 break;
302 }
303 }
304 mutex_unlock(&targets_mutex);
305
306 WARN_ON(found == false);
307}
308
309static void cache_btf_id(struct bpf_iter_target_info *tinfo,
310 struct bpf_prog *prog)
311{
312 tinfo->btf_id = prog->aux->attach_btf_id;
313}
314
315bool bpf_iter_prog_supported(struct bpf_prog *prog)
316{
317 const char *attach_fname = prog->aux->attach_func_name;
318 u32 prog_btf_id = prog->aux->attach_btf_id;
319 const char *prefix = BPF_ITER_FUNC_PREFIX;
320 struct bpf_iter_target_info *tinfo;
321 int prefix_len = strlen(prefix);
322 bool supported = false;
323
324 if (strncmp(attach_fname, prefix, prefix_len))
325 return false;
326
327 mutex_lock(&targets_mutex);
328 list_for_each_entry(tinfo, &targets, list) {
329 if (tinfo->btf_id && tinfo->btf_id == prog_btf_id) {
330 supported = true;
331 break;
332 }
333 if (!strcmp(attach_fname + prefix_len, tinfo->reg_info->target)) {
334 cache_btf_id(tinfo, prog);
335 supported = true;
336 break;
337 }
338 }
339 mutex_unlock(&targets_mutex);
340
341 if (supported) {
342 prog->aux->ctx_arg_info_size = tinfo->reg_info->ctx_arg_info_size;
343 prog->aux->ctx_arg_info = tinfo->reg_info->ctx_arg_info;
344 }
345
346 return supported;
347}
348
349static void bpf_iter_link_release(struct bpf_link *link)
350{
351 struct bpf_iter_link *iter_link =
352 container_of(link, struct bpf_iter_link, link);
353
354 if (iter_link->tinfo->reg_info->detach_target)
355 iter_link->tinfo->reg_info->detach_target(&iter_link->aux);
356}
357
358static void bpf_iter_link_dealloc(struct bpf_link *link)
359{
360 struct bpf_iter_link *iter_link =
361 container_of(link, struct bpf_iter_link, link);
362
363 kfree(iter_link);
364}
365
366static int bpf_iter_link_replace(struct bpf_link *link,
367 struct bpf_prog *new_prog,
368 struct bpf_prog *old_prog)
369{
370 int ret = 0;
371
372 mutex_lock(&link_mutex);
373 if (old_prog && link->prog != old_prog) {
374 ret = -EPERM;
375 goto out_unlock;
376 }
377
378 if (link->prog->type != new_prog->type ||
379 link->prog->expected_attach_type != new_prog->expected_attach_type ||
380 link->prog->aux->attach_btf_id != new_prog->aux->attach_btf_id) {
381 ret = -EINVAL;
382 goto out_unlock;
383 }
384
385 old_prog = xchg(&link->prog, new_prog);
386 bpf_prog_put(old_prog);
387
388out_unlock:
389 mutex_unlock(&link_mutex);
390 return ret;
391}
392
393static const struct bpf_link_ops bpf_iter_link_lops = {
394 .release = bpf_iter_link_release,
395 .dealloc = bpf_iter_link_dealloc,
396 .update_prog = bpf_iter_link_replace,
397};
398
399bool bpf_link_is_iter(struct bpf_link *link)
400{
401 return link->ops == &bpf_iter_link_lops;
402}
403
404int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
405{
406 union bpf_iter_link_info __user *ulinfo;
407 struct bpf_link_primer link_primer;
408 struct bpf_iter_target_info *tinfo;
409 union bpf_iter_link_info linfo;
410 struct bpf_iter_link *link;
411 u32 prog_btf_id, linfo_len;
412 bool existed = false;
413 int err;
414
415 if (attr->link_create.target_fd || attr->link_create.flags)
416 return -EINVAL;
417
418 memset(&linfo, 0, sizeof(union bpf_iter_link_info));
419
420 ulinfo = u64_to_user_ptr(attr->link_create.iter_info);
421 linfo_len = attr->link_create.iter_info_len;
422 if (!ulinfo ^ !linfo_len)
423 return -EINVAL;
424
425 if (ulinfo) {
426 err = bpf_check_uarg_tail_zero(ulinfo, sizeof(linfo),
427 linfo_len);
428 if (err)
429 return err;
430 linfo_len = min_t(u32, linfo_len, sizeof(linfo));
431 if (copy_from_user(&linfo, ulinfo, linfo_len))
432 return -EFAULT;
433 }
434
435 prog_btf_id = prog->aux->attach_btf_id;
436 mutex_lock(&targets_mutex);
437 list_for_each_entry(tinfo, &targets, list) {
438 if (tinfo->btf_id == prog_btf_id) {
439 existed = true;
440 break;
441 }
442 }
443 mutex_unlock(&targets_mutex);
444 if (!existed)
445 return -ENOENT;
446
447 link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
448 if (!link)
449 return -ENOMEM;
450
451 bpf_link_init(&link->link, BPF_LINK_TYPE_ITER, &bpf_iter_link_lops, prog);
452 link->tinfo = tinfo;
453
454 err = bpf_link_prime(&link->link, &link_primer);
455 if (err) {
456 kfree(link);
457 return err;
458 }
459
460 if (tinfo->reg_info->attach_target) {
461 err = tinfo->reg_info->attach_target(prog, &linfo, &link->aux);
462 if (err) {
463 bpf_link_cleanup(&link_primer);
464 return err;
465 }
466 }
467
468 return bpf_link_settle(&link_primer);
469}
470
471static void init_seq_meta(struct bpf_iter_priv_data *priv_data,
472 struct bpf_iter_target_info *tinfo,
473 const struct bpf_iter_seq_info *seq_info,
474 struct bpf_prog *prog)
475{
476 priv_data->tinfo = tinfo;
477 priv_data->seq_info = seq_info;
478 priv_data->prog = prog;
479 priv_data->session_id = atomic64_inc_return(&session_id);
480 priv_data->seq_num = 0;
481 priv_data->done_stop = false;
482}
483
484static int prepare_seq_file(struct file *file, struct bpf_iter_link *link,
485 const struct bpf_iter_seq_info *seq_info)
486{
487 struct bpf_iter_priv_data *priv_data;
488 struct bpf_iter_target_info *tinfo;
489 struct bpf_prog *prog;
490 u32 total_priv_dsize;
491 struct seq_file *seq;
492 int err = 0;
493
494 mutex_lock(&link_mutex);
495 prog = link->link.prog;
496 bpf_prog_inc(prog);
497 mutex_unlock(&link_mutex);
498
499 tinfo = link->tinfo;
500 total_priv_dsize = offsetof(struct bpf_iter_priv_data, target_private) +
501 seq_info->seq_priv_size;
502 priv_data = __seq_open_private(file, seq_info->seq_ops,
503 total_priv_dsize);
504 if (!priv_data) {
505 err = -ENOMEM;
506 goto release_prog;
507 }
508
509 if (seq_info->init_seq_private) {
510 err = seq_info->init_seq_private(priv_data->target_private, &link->aux);
511 if (err)
512 goto release_seq_file;
513 }
514
515 init_seq_meta(priv_data, tinfo, seq_info, prog);
516 seq = file->private_data;
517 seq->private = priv_data->target_private;
518
519 return 0;
520
521release_seq_file:
522 seq_release_private(file->f_inode, file);
523 file->private_data = NULL;
524release_prog:
525 bpf_prog_put(prog);
526 return err;
527}
528
529int bpf_iter_new_fd(struct bpf_link *link)
530{
531 struct bpf_iter_link *iter_link;
532 struct file *file;
533 unsigned int flags;
534 int err, fd;
535
536 if (link->ops != &bpf_iter_link_lops)
537 return -EINVAL;
538
539 flags = O_RDONLY | O_CLOEXEC;
540 fd = get_unused_fd_flags(flags);
541 if (fd < 0)
542 return fd;
543
544 file = anon_inode_getfile("bpf_iter", &bpf_iter_fops, NULL, flags);
545 if (IS_ERR(file)) {
546 err = PTR_ERR(file);
547 goto free_fd;
548 }
549
550 iter_link = container_of(link, struct bpf_iter_link, link);
551 err = prepare_seq_file(file, iter_link, __get_seq_info(iter_link));
552 if (err)
553 goto free_file;
554
555 fd_install(fd, file);
556 return fd;
557
558free_file:
559 fput(file);
560free_fd:
561 put_unused_fd(fd);
562 return err;
563}
564
565struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop)
566{
567 struct bpf_iter_priv_data *iter_priv;
568 struct seq_file *seq;
569 void *seq_priv;
570
571 seq = meta->seq;
572 if (seq->file->f_op != &bpf_iter_fops)
573 return NULL;
574
575 seq_priv = seq->private;
576 iter_priv = container_of(seq_priv, struct bpf_iter_priv_data,
577 target_private);
578
579 if (in_stop && iter_priv->done_stop)
580 return NULL;
581
582 meta->session_id = iter_priv->session_id;
583 meta->seq_num = iter_priv->seq_num;
584
585 return iter_priv->prog;
586}
587
588int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx)
589{
590 int ret;
591
592 rcu_read_lock();
593 migrate_disable();
594 ret = BPF_PROG_RUN(prog, ctx);
595 migrate_enable();
596 rcu_read_unlock();
597
598 /* bpf program can only return 0 or 1:
599 * 0 : okay
600 * 1 : retry the same object
601 * The bpf_iter_run_prog() return value
602 * will be seq_ops->show() return value.
603 */
604 return ret == 0 ? 0 : -EAGAIN;
605}