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