1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/bpf.h>
4 #include <linux/filter.h>
5 #include <net/net_namespace.h>
6
7 /*
8 * Functions to manage BPF programs attached to netns
9 */
10
11 struct bpf_netns_link {
12 struct bpf_link link;
13 enum bpf_attach_type type;
14 enum netns_bpf_attach_type netns_type;
15
16 /* We don't hold a ref to net in order to auto-detach the link
17 * when netns is going away. Instead we rely on pernet
18 * pre_exit callback to clear this pointer. Must be accessed
19 * with netns_bpf_mutex held.
20 */
21 struct net *net;
22 struct list_head node; /* node in list of links attached to net */
23 };
24
25 /* Protects updates to netns_bpf */
26 DEFINE_MUTEX(netns_bpf_mutex);
27
netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)28 static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
29 {
30 switch (type) {
31 #ifdef CONFIG_INET
32 case NETNS_BPF_SK_LOOKUP:
33 static_branch_dec(&bpf_sk_lookup_enabled);
34 break;
35 #endif
36 default:
37 break;
38 }
39 }
40
netns_bpf_attach_type_need(enum netns_bpf_attach_type type)41 static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type)
42 {
43 switch (type) {
44 #ifdef CONFIG_INET
45 case NETNS_BPF_SK_LOOKUP:
46 static_branch_inc(&bpf_sk_lookup_enabled);
47 break;
48 #endif
49 default:
50 break;
51 }
52 }
53
54 /* Must be called with netns_bpf_mutex held. */
netns_bpf_run_array_detach(struct net * net,enum netns_bpf_attach_type type)55 static void netns_bpf_run_array_detach(struct net *net,
56 enum netns_bpf_attach_type type)
57 {
58 struct bpf_prog_array *run_array;
59
60 run_array = rcu_replace_pointer(net->bpf.run_array[type], NULL,
61 lockdep_is_held(&netns_bpf_mutex));
62 bpf_prog_array_free(run_array);
63 }
64
link_index(struct net * net,enum netns_bpf_attach_type type,struct bpf_netns_link * link)65 static int link_index(struct net *net, enum netns_bpf_attach_type type,
66 struct bpf_netns_link *link)
67 {
68 struct bpf_netns_link *pos;
69 int i = 0;
70
71 list_for_each_entry(pos, &net->bpf.links[type], node) {
72 if (pos == link)
73 return i;
74 i++;
75 }
76 return -ENOENT;
77 }
78
link_count(struct net * net,enum netns_bpf_attach_type type)79 static int link_count(struct net *net, enum netns_bpf_attach_type type)
80 {
81 struct list_head *pos;
82 int i = 0;
83
84 list_for_each(pos, &net->bpf.links[type])
85 i++;
86 return i;
87 }
88
fill_prog_array(struct net * net,enum netns_bpf_attach_type type,struct bpf_prog_array * prog_array)89 static void fill_prog_array(struct net *net, enum netns_bpf_attach_type type,
90 struct bpf_prog_array *prog_array)
91 {
92 struct bpf_netns_link *pos;
93 unsigned int i = 0;
94
95 list_for_each_entry(pos, &net->bpf.links[type], node) {
96 prog_array->items[i].prog = pos->link.prog;
97 i++;
98 }
99 }
100
bpf_netns_link_release(struct bpf_link * link)101 static void bpf_netns_link_release(struct bpf_link *link)
102 {
103 struct bpf_netns_link *net_link =
104 container_of(link, struct bpf_netns_link, link);
105 enum netns_bpf_attach_type type = net_link->netns_type;
106 struct bpf_prog_array *old_array, *new_array;
107 struct net *net;
108 int cnt, idx;
109
110 mutex_lock(&netns_bpf_mutex);
111
112 /* We can race with cleanup_net, but if we see a non-NULL
113 * struct net pointer, pre_exit has not run yet and wait for
114 * netns_bpf_mutex.
115 */
116 net = net_link->net;
117 if (!net)
118 goto out_unlock;
119
120 /* Mark attach point as unused */
121 netns_bpf_attach_type_unneed(type);
122
123 /* Remember link position in case of safe delete */
124 idx = link_index(net, type, net_link);
125 list_del(&net_link->node);
126
127 cnt = link_count(net, type);
128 if (!cnt) {
129 netns_bpf_run_array_detach(net, type);
130 goto out_unlock;
131 }
132
133 old_array = rcu_dereference_protected(net->bpf.run_array[type],
134 lockdep_is_held(&netns_bpf_mutex));
135 new_array = bpf_prog_array_alloc(cnt, GFP_KERNEL);
136 if (!new_array) {
137 WARN_ON(bpf_prog_array_delete_safe_at(old_array, idx));
138 goto out_unlock;
139 }
140 fill_prog_array(net, type, new_array);
141 rcu_assign_pointer(net->bpf.run_array[type], new_array);
142 bpf_prog_array_free(old_array);
143
144 out_unlock:
145 net_link->net = NULL;
146 mutex_unlock(&netns_bpf_mutex);
147 }
148
bpf_netns_link_detach(struct bpf_link * link)149 static int bpf_netns_link_detach(struct bpf_link *link)
150 {
151 bpf_netns_link_release(link);
152 return 0;
153 }
154
bpf_netns_link_dealloc(struct bpf_link * link)155 static void bpf_netns_link_dealloc(struct bpf_link *link)
156 {
157 struct bpf_netns_link *net_link =
158 container_of(link, struct bpf_netns_link, link);
159
160 kfree(net_link);
161 }
162
bpf_netns_link_update_prog(struct bpf_link * link,struct bpf_prog * new_prog,struct bpf_prog * old_prog)163 static int bpf_netns_link_update_prog(struct bpf_link *link,
164 struct bpf_prog *new_prog,
165 struct bpf_prog *old_prog)
166 {
167 struct bpf_netns_link *net_link =
168 container_of(link, struct bpf_netns_link, link);
169 enum netns_bpf_attach_type type = net_link->netns_type;
170 struct bpf_prog_array *run_array;
171 struct net *net;
172 int idx, ret;
173
174 if (old_prog && old_prog != link->prog)
175 return -EPERM;
176 if (new_prog->type != link->prog->type)
177 return -EINVAL;
178
179 mutex_lock(&netns_bpf_mutex);
180
181 net = net_link->net;
182 if (!net || !check_net(net)) {
183 /* Link auto-detached or netns dying */
184 ret = -ENOLINK;
185 goto out_unlock;
186 }
187
188 run_array = rcu_dereference_protected(net->bpf.run_array[type],
189 lockdep_is_held(&netns_bpf_mutex));
190 idx = link_index(net, type, net_link);
191 ret = bpf_prog_array_update_at(run_array, idx, new_prog);
192 if (ret)
193 goto out_unlock;
194
195 old_prog = xchg(&link->prog, new_prog);
196 bpf_prog_put(old_prog);
197
198 out_unlock:
199 mutex_unlock(&netns_bpf_mutex);
200 return ret;
201 }
202
bpf_netns_link_fill_info(const struct bpf_link * link,struct bpf_link_info * info)203 static int bpf_netns_link_fill_info(const struct bpf_link *link,
204 struct bpf_link_info *info)
205 {
206 const struct bpf_netns_link *net_link =
207 container_of(link, struct bpf_netns_link, link);
208 unsigned int inum = 0;
209 struct net *net;
210
211 mutex_lock(&netns_bpf_mutex);
212 net = net_link->net;
213 if (net && check_net(net))
214 inum = net->ns.inum;
215 mutex_unlock(&netns_bpf_mutex);
216
217 info->netns.netns_ino = inum;
218 info->netns.attach_type = net_link->type;
219 return 0;
220 }
221
bpf_netns_link_show_fdinfo(const struct bpf_link * link,struct seq_file * seq)222 static void bpf_netns_link_show_fdinfo(const struct bpf_link *link,
223 struct seq_file *seq)
224 {
225 struct bpf_link_info info = {};
226
227 bpf_netns_link_fill_info(link, &info);
228 seq_printf(seq,
229 "netns_ino:\t%u\n"
230 "attach_type:\t%u\n",
231 info.netns.netns_ino,
232 info.netns.attach_type);
233 }
234
235 static const struct bpf_link_ops bpf_netns_link_ops = {
236 .release = bpf_netns_link_release,
237 .dealloc = bpf_netns_link_dealloc,
238 .detach = bpf_netns_link_detach,
239 .update_prog = bpf_netns_link_update_prog,
240 .fill_link_info = bpf_netns_link_fill_info,
241 .show_fdinfo = bpf_netns_link_show_fdinfo,
242 };
243
244 /* Must be called with netns_bpf_mutex held. */
__netns_bpf_prog_query(const union bpf_attr * attr,union bpf_attr __user * uattr,struct net * net,enum netns_bpf_attach_type type)245 static int __netns_bpf_prog_query(const union bpf_attr *attr,
246 union bpf_attr __user *uattr,
247 struct net *net,
248 enum netns_bpf_attach_type type)
249 {
250 __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
251 struct bpf_prog_array *run_array;
252 u32 prog_cnt = 0, flags = 0;
253
254 run_array = rcu_dereference_protected(net->bpf.run_array[type],
255 lockdep_is_held(&netns_bpf_mutex));
256 if (run_array)
257 prog_cnt = bpf_prog_array_length(run_array);
258
259 if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
260 return -EFAULT;
261 if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
262 return -EFAULT;
263 if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
264 return 0;
265
266 return bpf_prog_array_copy_to_user(run_array, prog_ids,
267 attr->query.prog_cnt);
268 }
269
netns_bpf_prog_query(const union bpf_attr * attr,union bpf_attr __user * uattr)270 int netns_bpf_prog_query(const union bpf_attr *attr,
271 union bpf_attr __user *uattr)
272 {
273 enum netns_bpf_attach_type type;
274 struct net *net;
275 int ret;
276
277 if (attr->query.query_flags)
278 return -EINVAL;
279
280 type = to_netns_bpf_attach_type(attr->query.attach_type);
281 if (type < 0)
282 return -EINVAL;
283
284 net = get_net_ns_by_fd(attr->query.target_fd);
285 if (IS_ERR(net))
286 return PTR_ERR(net);
287
288 mutex_lock(&netns_bpf_mutex);
289 ret = __netns_bpf_prog_query(attr, uattr, net, type);
290 mutex_unlock(&netns_bpf_mutex);
291
292 put_net(net);
293 return ret;
294 }
295
netns_bpf_prog_attach(const union bpf_attr * attr,struct bpf_prog * prog)296 int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
297 {
298 struct bpf_prog_array *run_array;
299 enum netns_bpf_attach_type type;
300 struct bpf_prog *attached;
301 struct net *net;
302 int ret;
303
304 if (attr->target_fd || attr->attach_flags || attr->replace_bpf_fd)
305 return -EINVAL;
306
307 type = to_netns_bpf_attach_type(attr->attach_type);
308 if (type < 0)
309 return -EINVAL;
310
311 net = current->nsproxy->net_ns;
312 mutex_lock(&netns_bpf_mutex);
313
314 /* Attaching prog directly is not compatible with links */
315 if (!list_empty(&net->bpf.links[type])) {
316 ret = -EEXIST;
317 goto out_unlock;
318 }
319
320 switch (type) {
321 case NETNS_BPF_FLOW_DISSECTOR:
322 ret = flow_dissector_bpf_prog_attach_check(net, prog);
323 break;
324 default:
325 ret = -EINVAL;
326 break;
327 }
328 if (ret)
329 goto out_unlock;
330
331 attached = net->bpf.progs[type];
332 if (attached == prog) {
333 /* The same program cannot be attached twice */
334 ret = -EINVAL;
335 goto out_unlock;
336 }
337
338 run_array = rcu_dereference_protected(net->bpf.run_array[type],
339 lockdep_is_held(&netns_bpf_mutex));
340 if (run_array) {
341 WRITE_ONCE(run_array->items[0].prog, prog);
342 } else {
343 run_array = bpf_prog_array_alloc(1, GFP_KERNEL);
344 if (!run_array) {
345 ret = -ENOMEM;
346 goto out_unlock;
347 }
348 run_array->items[0].prog = prog;
349 rcu_assign_pointer(net->bpf.run_array[type], run_array);
350 }
351
352 net->bpf.progs[type] = prog;
353 if (attached)
354 bpf_prog_put(attached);
355
356 out_unlock:
357 mutex_unlock(&netns_bpf_mutex);
358
359 return ret;
360 }
361
362 /* Must be called with netns_bpf_mutex held. */
__netns_bpf_prog_detach(struct net * net,enum netns_bpf_attach_type type,struct bpf_prog * old)363 static int __netns_bpf_prog_detach(struct net *net,
364 enum netns_bpf_attach_type type,
365 struct bpf_prog *old)
366 {
367 struct bpf_prog *attached;
368
369 /* Progs attached via links cannot be detached */
370 if (!list_empty(&net->bpf.links[type]))
371 return -EINVAL;
372
373 attached = net->bpf.progs[type];
374 if (!attached || attached != old)
375 return -ENOENT;
376 netns_bpf_run_array_detach(net, type);
377 net->bpf.progs[type] = NULL;
378 bpf_prog_put(attached);
379 return 0;
380 }
381
netns_bpf_prog_detach(const union bpf_attr * attr,enum bpf_prog_type ptype)382 int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
383 {
384 enum netns_bpf_attach_type type;
385 struct bpf_prog *prog;
386 int ret;
387
388 if (attr->target_fd)
389 return -EINVAL;
390
391 type = to_netns_bpf_attach_type(attr->attach_type);
392 if (type < 0)
393 return -EINVAL;
394
395 prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
396 if (IS_ERR(prog))
397 return PTR_ERR(prog);
398
399 mutex_lock(&netns_bpf_mutex);
400 ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
401 mutex_unlock(&netns_bpf_mutex);
402
403 bpf_prog_put(prog);
404
405 return ret;
406 }
407
netns_bpf_max_progs(enum netns_bpf_attach_type type)408 static int netns_bpf_max_progs(enum netns_bpf_attach_type type)
409 {
410 switch (type) {
411 case NETNS_BPF_FLOW_DISSECTOR:
412 return 1;
413 case NETNS_BPF_SK_LOOKUP:
414 return 64;
415 default:
416 return 0;
417 }
418 }
419
netns_bpf_link_attach(struct net * net,struct bpf_link * link,enum netns_bpf_attach_type type)420 static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
421 enum netns_bpf_attach_type type)
422 {
423 struct bpf_netns_link *net_link =
424 container_of(link, struct bpf_netns_link, link);
425 struct bpf_prog_array *run_array;
426 int cnt, err;
427
428 mutex_lock(&netns_bpf_mutex);
429
430 cnt = link_count(net, type);
431 if (cnt >= netns_bpf_max_progs(type)) {
432 err = -E2BIG;
433 goto out_unlock;
434 }
435 /* Links are not compatible with attaching prog directly */
436 if (net->bpf.progs[type]) {
437 err = -EEXIST;
438 goto out_unlock;
439 }
440
441 switch (type) {
442 case NETNS_BPF_FLOW_DISSECTOR:
443 err = flow_dissector_bpf_prog_attach_check(net, link->prog);
444 break;
445 case NETNS_BPF_SK_LOOKUP:
446 err = 0; /* nothing to check */
447 break;
448 default:
449 err = -EINVAL;
450 break;
451 }
452 if (err)
453 goto out_unlock;
454
455 run_array = bpf_prog_array_alloc(cnt + 1, GFP_KERNEL);
456 if (!run_array) {
457 err = -ENOMEM;
458 goto out_unlock;
459 }
460
461 list_add_tail(&net_link->node, &net->bpf.links[type]);
462
463 fill_prog_array(net, type, run_array);
464 run_array = rcu_replace_pointer(net->bpf.run_array[type], run_array,
465 lockdep_is_held(&netns_bpf_mutex));
466 bpf_prog_array_free(run_array);
467
468 /* Mark attach point as used */
469 netns_bpf_attach_type_need(type);
470
471 out_unlock:
472 mutex_unlock(&netns_bpf_mutex);
473 return err;
474 }
475
netns_bpf_link_create(const union bpf_attr * attr,struct bpf_prog * prog)476 int netns_bpf_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
477 {
478 enum netns_bpf_attach_type netns_type;
479 struct bpf_link_primer link_primer;
480 struct bpf_netns_link *net_link;
481 enum bpf_attach_type type;
482 struct net *net;
483 int err;
484
485 if (attr->link_create.flags)
486 return -EINVAL;
487
488 type = attr->link_create.attach_type;
489 netns_type = to_netns_bpf_attach_type(type);
490 if (netns_type < 0)
491 return -EINVAL;
492
493 net = get_net_ns_by_fd(attr->link_create.target_fd);
494 if (IS_ERR(net))
495 return PTR_ERR(net);
496
497 net_link = kzalloc(sizeof(*net_link), GFP_USER);
498 if (!net_link) {
499 err = -ENOMEM;
500 goto out_put_net;
501 }
502 bpf_link_init(&net_link->link, BPF_LINK_TYPE_NETNS,
503 &bpf_netns_link_ops, prog);
504 net_link->net = net;
505 net_link->type = type;
506 net_link->netns_type = netns_type;
507
508 err = bpf_link_prime(&net_link->link, &link_primer);
509 if (err) {
510 kfree(net_link);
511 goto out_put_net;
512 }
513
514 err = netns_bpf_link_attach(net, &net_link->link, netns_type);
515 if (err) {
516 bpf_link_cleanup(&link_primer);
517 goto out_put_net;
518 }
519
520 put_net(net);
521 return bpf_link_settle(&link_primer);
522
523 out_put_net:
524 put_net(net);
525 return err;
526 }
527
netns_bpf_pernet_init(struct net * net)528 static int __net_init netns_bpf_pernet_init(struct net *net)
529 {
530 int type;
531
532 for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)
533 INIT_LIST_HEAD(&net->bpf.links[type]);
534
535 return 0;
536 }
537
netns_bpf_pernet_pre_exit(struct net * net)538 static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)
539 {
540 enum netns_bpf_attach_type type;
541 struct bpf_netns_link *net_link;
542
543 mutex_lock(&netns_bpf_mutex);
544 for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {
545 netns_bpf_run_array_detach(net, type);
546 list_for_each_entry(net_link, &net->bpf.links[type], node) {
547 net_link->net = NULL; /* auto-detach link */
548 netns_bpf_attach_type_unneed(type);
549 }
550 if (net->bpf.progs[type])
551 bpf_prog_put(net->bpf.progs[type]);
552 }
553 mutex_unlock(&netns_bpf_mutex);
554 }
555
556 static struct pernet_operations netns_bpf_pernet_ops __net_initdata = {
557 .init = netns_bpf_pernet_init,
558 .pre_exit = netns_bpf_pernet_pre_exit,
559 };
560
netns_bpf_init(void)561 static int __init netns_bpf_init(void)
562 {
563 return register_pernet_subsys(&netns_bpf_pernet_ops);
564 }
565
566 subsys_initcall(netns_bpf_init);
567