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
 11struct 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 */
 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	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
198out_unlock:
199	mutex_unlock(&netns_bpf_mutex);
200	return ret;
201}
202
203static 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
222static 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
235static 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. */
245static 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
270int 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
296int 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
356out_unlock:
357	mutex_unlock(&netns_bpf_mutex);
358
359	return ret;
360}
361
362/* Must be called with netns_bpf_mutex held. */
363static 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
382int 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
408static 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
420static 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
471out_unlock:
472	mutex_unlock(&netns_bpf_mutex);
473	return err;
474}
475
476int 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
523out_put_net:
524	put_net(net);
525	return err;
526}
527
528static 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
538static 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
556static 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
561static int __init netns_bpf_init(void)
562{
563	return register_pernet_subsys(&netns_bpf_pernet_ops);
564}
565
566subsys_initcall(netns_bpf_init);