1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (c) 2021 Cong Wang <cong.wang@bytedance.com> */
3
4#include <linux/bpf.h>
5#include <linux/skmsg.h>
6#include <net/af_unix.h>
7
8#include "af_unix.h"
9
10#define unix_sk_has_data(__sk, __psock) \
11 ({ !skb_queue_empty(&__sk->sk_receive_queue) || \
12 !skb_queue_empty(&__psock->ingress_skb) || \
13 !list_empty(&__psock->ingress_msg); \
14 })
15
16static int unix_msg_wait_data(struct sock *sk, struct sk_psock *psock,
17 long timeo)
18{
19 DEFINE_WAIT_FUNC(wait, woken_wake_function);
20 struct unix_sock *u = unix_sk(sk);
21 int ret = 0;
22
23 if (sk->sk_shutdown & RCV_SHUTDOWN)
24 return 1;
25
26 if (!timeo)
27 return ret;
28
29 add_wait_queue(wq_head: sk_sleep(sk), wq_entry: &wait);
30 sk_set_bit(nr: SOCKWQ_ASYNC_WAITDATA, sk);
31 if (!unix_sk_has_data(sk, psock)) {
32 mutex_unlock(lock: &u->iolock);
33 wait_woken(wq_entry: &wait, TASK_INTERRUPTIBLE, timeout: timeo);
34 mutex_lock(&u->iolock);
35 ret = unix_sk_has_data(sk, psock);
36 }
37 sk_clear_bit(nr: SOCKWQ_ASYNC_WAITDATA, sk);
38 remove_wait_queue(wq_head: sk_sleep(sk), wq_entry: &wait);
39 return ret;
40}
41
42static int __unix_recvmsg(struct sock *sk, struct msghdr *msg,
43 size_t len, int flags)
44{
45 if (sk->sk_type == SOCK_DGRAM)
46 return __unix_dgram_recvmsg(sk, msg, size: len, flags);
47 else
48 return __unix_stream_recvmsg(sk, msg, size: len, flags);
49}
50
51static int unix_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
52 size_t len, int flags, int *addr_len)
53{
54 struct unix_sock *u = unix_sk(sk);
55 struct sk_psock *psock;
56 int copied;
57
58 if (flags & MSG_OOB)
59 return -EOPNOTSUPP;
60
61 if (!len)
62 return 0;
63
64 psock = sk_psock_get(sk);
65 if (unlikely(!psock))
66 return __unix_recvmsg(sk, msg, len, flags);
67
68 mutex_lock(&u->iolock);
69 if (!skb_queue_empty(list: &sk->sk_receive_queue) &&
70 sk_psock_queue_empty(psock)) {
71 mutex_unlock(lock: &u->iolock);
72 sk_psock_put(sk, psock);
73 return __unix_recvmsg(sk, msg, len, flags);
74 }
75
76msg_bytes_ready:
77 copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
78 if (!copied) {
79 long timeo;
80 int data;
81
82 timeo = sock_rcvtimeo(sk, noblock: flags & MSG_DONTWAIT);
83 data = unix_msg_wait_data(sk, psock, timeo);
84 if (data) {
85 if (!sk_psock_queue_empty(psock))
86 goto msg_bytes_ready;
87 mutex_unlock(lock: &u->iolock);
88 sk_psock_put(sk, psock);
89 return __unix_recvmsg(sk, msg, len, flags);
90 }
91 copied = -EAGAIN;
92 }
93 mutex_unlock(lock: &u->iolock);
94 sk_psock_put(sk, psock);
95 return copied;
96}
97
98static struct proto *unix_dgram_prot_saved __read_mostly;
99static DEFINE_SPINLOCK(unix_dgram_prot_lock);
100static struct proto unix_dgram_bpf_prot;
101
102static struct proto *unix_stream_prot_saved __read_mostly;
103static DEFINE_SPINLOCK(unix_stream_prot_lock);
104static struct proto unix_stream_bpf_prot;
105
106static void unix_dgram_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
107{
108 *prot = *base;
109 prot->close = sock_map_close;
110 prot->recvmsg = unix_bpf_recvmsg;
111 prot->sock_is_readable = sk_msg_is_readable;
112}
113
114static void unix_stream_bpf_rebuild_protos(struct proto *prot,
115 const struct proto *base)
116{
117 *prot = *base;
118 prot->close = sock_map_close;
119 prot->recvmsg = unix_bpf_recvmsg;
120 prot->sock_is_readable = sk_msg_is_readable;
121 prot->unhash = sock_map_unhash;
122}
123
124static void unix_dgram_bpf_check_needs_rebuild(struct proto *ops)
125{
126 if (unlikely(ops != smp_load_acquire(&unix_dgram_prot_saved))) {
127 spin_lock_bh(lock: &unix_dgram_prot_lock);
128 if (likely(ops != unix_dgram_prot_saved)) {
129 unix_dgram_bpf_rebuild_protos(prot: &unix_dgram_bpf_prot, base: ops);
130 smp_store_release(&unix_dgram_prot_saved, ops);
131 }
132 spin_unlock_bh(lock: &unix_dgram_prot_lock);
133 }
134}
135
136static void unix_stream_bpf_check_needs_rebuild(struct proto *ops)
137{
138 if (unlikely(ops != smp_load_acquire(&unix_stream_prot_saved))) {
139 spin_lock_bh(lock: &unix_stream_prot_lock);
140 if (likely(ops != unix_stream_prot_saved)) {
141 unix_stream_bpf_rebuild_protos(prot: &unix_stream_bpf_prot, base: ops);
142 smp_store_release(&unix_stream_prot_saved, ops);
143 }
144 spin_unlock_bh(lock: &unix_stream_prot_lock);
145 }
146}
147
148int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
149{
150 if (sk->sk_type != SOCK_DGRAM)
151 return -EOPNOTSUPP;
152
153 if (restore) {
154 sk->sk_write_space = psock->saved_write_space;
155 sock_replace_proto(sk, proto: psock->sk_proto);
156 return 0;
157 }
158
159 unix_dgram_bpf_check_needs_rebuild(ops: psock->sk_proto);
160 sock_replace_proto(sk, proto: &unix_dgram_bpf_prot);
161 return 0;
162}
163
164int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
165{
166 struct sock *sk_pair;
167
168 /* Restore does not decrement the sk_pair reference yet because we must
169 * keep the a reference to the socket until after an RCU grace period
170 * and any pending sends have completed.
171 */
172 if (restore) {
173 sk->sk_write_space = psock->saved_write_space;
174 sock_replace_proto(sk, proto: psock->sk_proto);
175 return 0;
176 }
177
178 /* psock_update_sk_prot can be called multiple times if psock is
179 * added to multiple maps and/or slots in the same map. There is
180 * also an edge case where replacing a psock with itself can trigger
181 * an extra psock_update_sk_prot during the insert process. So it
182 * must be safe to do multiple calls. Here we need to ensure we don't
183 * increment the refcnt through sock_hold many times. There will only
184 * be a single matching destroy operation.
185 */
186 if (!psock->sk_pair) {
187 sk_pair = unix_peer(sk);
188 sock_hold(sk: sk_pair);
189 psock->sk_pair = sk_pair;
190 }
191
192 unix_stream_bpf_check_needs_rebuild(ops: psock->sk_proto);
193 sock_replace_proto(sk, proto: &unix_stream_bpf_prot);
194 return 0;
195}
196
197void __init unix_bpf_build_proto(void)
198{
199 unix_dgram_bpf_rebuild_protos(prot: &unix_dgram_bpf_prot, base: &unix_dgram_proto);
200 unix_stream_bpf_rebuild_protos(prot: &unix_stream_bpf_prot, base: &unix_stream_proto);
201
202}
203

source code of linux/net/unix/unix_bpf.c