1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Generic netlink handshake service
4 *
5 * Author: Chuck Lever <chuck.lever@oracle.com>
6 *
7 * Copyright (c) 2023, Oracle and/or its affiliates.
8 */
9
10 #include <linux/types.h>
11 #include <linux/socket.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/skbuff.h>
15 #include <linux/mm.h>
16
17 #include <net/sock.h>
18 #include <net/genetlink.h>
19 #include <net/netns/generic.h>
20
21 #include <kunit/visibility.h>
22
23 #include <uapi/linux/handshake.h>
24 #include "handshake.h"
25 #include "genl.h"
26
27 #include <trace/events/handshake.h>
28
29 /**
30 * handshake_genl_notify - Notify handlers that a request is waiting
31 * @net: target network namespace
32 * @proto: handshake protocol
33 * @flags: memory allocation control flags
34 *
35 * Returns zero on success or a negative errno if notification failed.
36 */
handshake_genl_notify(struct net * net,const struct handshake_proto * proto,gfp_t flags)37 int handshake_genl_notify(struct net *net, const struct handshake_proto *proto,
38 gfp_t flags)
39 {
40 struct sk_buff *msg;
41 void *hdr;
42
43 /* Disable notifications during unit testing */
44 if (!test_bit(HANDSHAKE_F_PROTO_NOTIFY, &proto->hp_flags))
45 return 0;
46
47 if (!genl_has_listeners(&handshake_nl_family, net,
48 proto->hp_handler_class))
49 return -ESRCH;
50
51 msg = genlmsg_new(GENLMSG_DEFAULT_SIZE, flags);
52 if (!msg)
53 return -ENOMEM;
54
55 hdr = genlmsg_put(msg, 0, 0, &handshake_nl_family, 0,
56 HANDSHAKE_CMD_READY);
57 if (!hdr)
58 goto out_free;
59
60 if (nla_put_u32(msg, HANDSHAKE_A_ACCEPT_HANDLER_CLASS,
61 proto->hp_handler_class) < 0) {
62 genlmsg_cancel(msg, hdr);
63 goto out_free;
64 }
65
66 genlmsg_end(msg, hdr);
67 return genlmsg_multicast_netns(&handshake_nl_family, net, msg,
68 0, proto->hp_handler_class, flags);
69
70 out_free:
71 nlmsg_free(msg);
72 return -EMSGSIZE;
73 }
74
75 /**
76 * handshake_genl_put - Create a generic netlink message header
77 * @msg: buffer in which to create the header
78 * @info: generic netlink message context
79 *
80 * Returns a ready-to-use header, or NULL.
81 */
handshake_genl_put(struct sk_buff * msg,struct genl_info * info)82 struct nlmsghdr *handshake_genl_put(struct sk_buff *msg,
83 struct genl_info *info)
84 {
85 return genlmsg_put(msg, info->snd_portid, info->snd_seq,
86 &handshake_nl_family, 0, info->genlhdr->cmd);
87 }
88 EXPORT_SYMBOL(handshake_genl_put);
89
handshake_nl_accept_doit(struct sk_buff * skb,struct genl_info * info)90 int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)
91 {
92 struct net *net = sock_net(skb->sk);
93 struct handshake_net *hn = handshake_pernet(net);
94 struct handshake_req *req = NULL;
95 struct socket *sock;
96 int class, fd, err;
97
98 err = -EOPNOTSUPP;
99 if (!hn)
100 goto out_status;
101
102 err = -EINVAL;
103 if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_ACCEPT_HANDLER_CLASS))
104 goto out_status;
105 class = nla_get_u32(info->attrs[HANDSHAKE_A_ACCEPT_HANDLER_CLASS]);
106
107 err = -EAGAIN;
108 req = handshake_req_next(hn, class);
109 if (!req)
110 goto out_status;
111
112 sock = req->hr_sk->sk_socket;
113 fd = get_unused_fd_flags(O_CLOEXEC);
114 if (fd < 0) {
115 err = fd;
116 goto out_complete;
117 }
118
119 err = req->hr_proto->hp_accept(req, info, fd);
120 if (err) {
121 put_unused_fd(fd);
122 goto out_complete;
123 }
124
125 fd_install(fd, get_file(sock->file));
126
127 trace_handshake_cmd_accept(net, req, req->hr_sk, fd);
128 return 0;
129
130 out_complete:
131 handshake_complete(req, -EIO, NULL);
132 out_status:
133 trace_handshake_cmd_accept_err(net, req, NULL, err);
134 return err;
135 }
136
handshake_nl_done_doit(struct sk_buff * skb,struct genl_info * info)137 int handshake_nl_done_doit(struct sk_buff *skb, struct genl_info *info)
138 {
139 struct net *net = sock_net(skb->sk);
140 struct handshake_req *req;
141 struct socket *sock;
142 int fd, status, err;
143
144 if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_DONE_SOCKFD))
145 return -EINVAL;
146 fd = nla_get_s32(info->attrs[HANDSHAKE_A_DONE_SOCKFD]);
147
148 sock = sockfd_lookup(fd, &err);
149 if (!sock)
150 return err;
151
152 req = handshake_req_hash_lookup(sock->sk);
153 if (!req) {
154 err = -EBUSY;
155 trace_handshake_cmd_done_err(net, req, sock->sk, err);
156 sockfd_put(sock);
157 return err;
158 }
159
160 trace_handshake_cmd_done(net, req, sock->sk, fd);
161
162 status = -EIO;
163 if (info->attrs[HANDSHAKE_A_DONE_STATUS])
164 status = nla_get_u32(info->attrs[HANDSHAKE_A_DONE_STATUS]);
165
166 handshake_complete(req, status, info);
167 sockfd_put(sock);
168 return 0;
169 }
170
171 static unsigned int handshake_net_id;
172
handshake_net_init(struct net * net)173 static int __net_init handshake_net_init(struct net *net)
174 {
175 struct handshake_net *hn = net_generic(net, handshake_net_id);
176 unsigned long tmp;
177 struct sysinfo si;
178
179 /*
180 * Arbitrary limit to prevent handshakes that do not make
181 * progress from clogging up the system. The cap scales up
182 * with the amount of physical memory on the system.
183 */
184 si_meminfo(&si);
185 tmp = si.totalram / (25 * si.mem_unit);
186 hn->hn_pending_max = clamp(tmp, 3UL, 50UL);
187
188 spin_lock_init(&hn->hn_lock);
189 hn->hn_pending = 0;
190 hn->hn_flags = 0;
191 INIT_LIST_HEAD(&hn->hn_requests);
192 return 0;
193 }
194
handshake_net_exit(struct net * net)195 static void __net_exit handshake_net_exit(struct net *net)
196 {
197 struct handshake_net *hn = net_generic(net, handshake_net_id);
198 struct handshake_req *req;
199 LIST_HEAD(requests);
200
201 /*
202 * Drain the net's pending list. Requests that have been
203 * accepted and are in progress will be destroyed when
204 * the socket is closed.
205 */
206 spin_lock(&hn->hn_lock);
207 set_bit(HANDSHAKE_F_NET_DRAINING, &hn->hn_flags);
208 list_splice_init(&requests, &hn->hn_requests);
209 spin_unlock(&hn->hn_lock);
210
211 while (!list_empty(&requests)) {
212 req = list_first_entry(&requests, struct handshake_req, hr_list);
213 list_del(&req->hr_list);
214
215 /*
216 * Requests on this list have not yet been
217 * accepted, so they do not have an fd to put.
218 */
219
220 handshake_complete(req, -ETIMEDOUT, NULL);
221 }
222 }
223
224 static struct pernet_operations handshake_genl_net_ops = {
225 .init = handshake_net_init,
226 .exit = handshake_net_exit,
227 .id = &handshake_net_id,
228 .size = sizeof(struct handshake_net),
229 };
230
231 /**
232 * handshake_pernet - Get the handshake private per-net structure
233 * @net: network namespace
234 *
235 * Returns a pointer to the net's private per-net structure for the
236 * handshake module, or NULL if handshake_init() failed.
237 */
handshake_pernet(struct net * net)238 struct handshake_net *handshake_pernet(struct net *net)
239 {
240 return handshake_net_id ?
241 net_generic(net, handshake_net_id) : NULL;
242 }
243 EXPORT_SYMBOL_IF_KUNIT(handshake_pernet);
244
handshake_init(void)245 static int __init handshake_init(void)
246 {
247 int ret;
248
249 ret = handshake_req_hash_init();
250 if (ret) {
251 pr_warn("handshake: hash initialization failed (%d)\n", ret);
252 return ret;
253 }
254
255 ret = genl_register_family(&handshake_nl_family);
256 if (ret) {
257 pr_warn("handshake: netlink registration failed (%d)\n", ret);
258 handshake_req_hash_destroy();
259 return ret;
260 }
261
262 /*
263 * ORDER: register_pernet_subsys must be done last.
264 *
265 * If initialization does not make it past pernet_subsys
266 * registration, then handshake_net_id will remain 0. That
267 * shunts the handshake consumer API to return ENOTSUPP
268 * to prevent it from dereferencing something that hasn't
269 * been allocated.
270 */
271 ret = register_pernet_subsys(&handshake_genl_net_ops);
272 if (ret) {
273 pr_warn("handshake: pernet registration failed (%d)\n", ret);
274 genl_unregister_family(&handshake_nl_family);
275 handshake_req_hash_destroy();
276 }
277
278 return ret;
279 }
280
handshake_exit(void)281 static void __exit handshake_exit(void)
282 {
283 unregister_pernet_subsys(&handshake_genl_net_ops);
284 handshake_net_id = 0;
285
286 handshake_req_hash_destroy();
287 genl_unregister_family(&handshake_nl_family);
288 }
289
290 module_init(handshake_init);
291 module_exit(handshake_exit);
292