1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021 Cong Wang <cong.wang@bytedance.com> */
3
4 #include <linux/skmsg.h>
5 #include <linux/bpf.h>
6 #include <net/sock.h>
7 #include <net/af_unix.h>
8
9 #define unix_sk_has_data(__sk, __psock) \
10 ({ !skb_queue_empty(&__sk->sk_receive_queue) || \
11 !skb_queue_empty(&__psock->ingress_skb) || \
12 !list_empty(&__psock->ingress_msg); \
13 })
14
15 static int unix_msg_wait_data(struct sock *sk, struct sk_psock *psock,
16 long timeo)
17 {
18 DEFINE_WAIT_FUNC(wait, woken_wake_function);
19 struct unix_sock *u = unix_sk(sk);
20 int ret = 0;
21
22 if (sk->sk_shutdown & RCV_SHUTDOWN)
23 return 1;
24
25 if (!timeo)
26 return ret;
27
28 add_wait_queue(sk_sleep(sk), &wait);
29 sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
30 if (!unix_sk_has_data(sk, psock)) {
31 mutex_unlock(&u->iolock);
32 wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
33 mutex_lock(&u->iolock);
34 ret = unix_sk_has_data(sk, psock);
35 }
36 sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
37 remove_wait_queue(sk_sleep(sk), &wait);
38 return ret;
39 }
40
41 static int __unix_recvmsg(struct sock *sk, struct msghdr *msg,
42 size_t len, int flags)
43 {
44 if (sk->sk_type == SOCK_DGRAM)
45 return __unix_dgram_recvmsg(sk, msg, len, flags);
46 else
47 return __unix_stream_recvmsg(sk, msg, len, flags);
48 }
49
50 static int unix_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
51 size_t len, int flags, int *addr_len)
52 {
53 struct unix_sock *u = unix_sk(sk);
54 struct sk_psock *psock;
55 int copied;
56
57 if (flags & MSG_OOB)
58 return -EOPNOTSUPP;
59
60 if (!len)
61 return 0;
62
63 psock = sk_psock_get(sk);
64 if (unlikely(!psock))
65 return __unix_recvmsg(sk, msg, len, flags);
66
67 mutex_lock(&u->iolock);
68 if (!skb_queue_empty(&sk->sk_receive_queue) &&
69 sk_psock_queue_empty(psock)) {
70 mutex_unlock(&u->iolock);
71 sk_psock_put(sk, psock);
72 return __unix_recvmsg(sk, msg, len, flags);
73 }
74
75 msg_bytes_ready:
76 copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
77 if (!copied) {
78 long timeo;
79 int data;
80
81 timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
82 data = unix_msg_wait_data(sk, psock, timeo);
83 if (data) {
84 if (!sk_psock_queue_empty(psock))
85 goto msg_bytes_ready;
86 mutex_unlock(&u->iolock);
87 sk_psock_put(sk, psock);
88 return __unix_recvmsg(sk, msg, len, flags);
89 }
90 copied = -EAGAIN;
91 }
92 mutex_unlock(&u->iolock);
93 sk_psock_put(sk, psock);
94 return copied;
95 }
96
97 static struct proto *unix_dgram_prot_saved __read_mostly;
98 static DEFINE_SPINLOCK(unix_dgram_prot_lock);
99 static struct proto unix_dgram_bpf_prot;
100
101 static struct proto *unix_stream_prot_saved __read_mostly;
102 static DEFINE_SPINLOCK(unix_stream_prot_lock);
103 static struct proto unix_stream_bpf_prot;
104
105 static void unix_dgram_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
106 {
107 *prot = *base;
108 prot->close = sock_map_close;
109 prot->recvmsg = unix_bpf_recvmsg;
110 prot->sock_is_readable = sk_msg_is_readable;
111 }
112
113 static void unix_stream_bpf_rebuild_protos(struct proto *prot,
114 const struct proto *base)
115 {
116 *prot = *base;
117 prot->close = sock_map_close;
118 prot->recvmsg = unix_bpf_recvmsg;
119 prot->sock_is_readable = sk_msg_is_readable;
120 prot->unhash = sock_map_unhash;
121 }
122
123 static void unix_dgram_bpf_check_needs_rebuild(struct proto *ops)
124 {
125 if (unlikely(ops != smp_load_acquire(&unix_dgram_prot_saved))) {
126 spin_lock_bh(&unix_dgram_prot_lock);
127 if (likely(ops != unix_dgram_prot_saved)) {
128 unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, ops);
129 smp_store_release(&unix_dgram_prot_saved, ops);
130 }
131 spin_unlock_bh(&unix_dgram_prot_lock);
132 }
133 }
134
135 static void unix_stream_bpf_check_needs_rebuild(struct proto *ops)
136 {
137 if (unlikely(ops != smp_load_acquire(&unix_stream_prot_saved))) {
138 spin_lock_bh(&unix_stream_prot_lock);
139 if (likely(ops != unix_stream_prot_saved)) {
140 unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, ops);
141 smp_store_release(&unix_stream_prot_saved, ops);
142 }
143 spin_unlock_bh(&unix_stream_prot_lock);
144 }
145 }
146
147 int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
148 {
149 if (sk->sk_type != SOCK_DGRAM)
150 return -EOPNOTSUPP;
151
152 if (restore) {
153 sk->sk_write_space = psock->saved_write_space;
154 sock_replace_proto(sk, psock->sk_proto);
155 return 0;
156 }
157
158 unix_dgram_bpf_check_needs_rebuild(psock->sk_proto);
159 sock_replace_proto(sk, &unix_dgram_bpf_prot);
160 return 0;
161 }
162
163 int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
164 {
165 struct sock *sk_pair;
166
167 /* Restore does not decrement the sk_pair reference yet because we must
168 * keep the a reference to the socket until after an RCU grace period
169 * and any pending sends have completed.
170 */
171 if (restore) {
172 sk->sk_write_space = psock->saved_write_space;
173 sock_replace_proto(sk, psock->sk_proto);
174 return 0;
175 }
176
177 /* psock_update_sk_prot can be called multiple times if psock is
178 * added to multiple maps and/or slots in the same map. There is
179 * also an edge case where replacing a psock with itself can trigger
180 * an extra psock_update_sk_prot during the insert process. So it
181 * must be safe to do multiple calls. Here we need to ensure we don't
182 * increment the refcnt through sock_hold many times. There will only
183 * be a single matching destroy operation.
184 */
185 if (!psock->sk_pair) {
186 sk_pair = unix_peer(sk);
187 sock_hold(sk_pair);
188 psock->sk_pair = sk_pair;
189 }
190
191 unix_stream_bpf_check_needs_rebuild(psock->sk_proto);
192 sock_replace_proto(sk, &unix_stream_bpf_prot);
193 return 0;
194 }
195
196 void __init unix_bpf_build_proto(void)
197 {
198 unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, &unix_dgram_proto);
199 unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, &unix_stream_proto);
200
201 }
202
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