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
 15static 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
 41static 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
 50static 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	psock = sk_psock_get(sk);
 58	if (unlikely(!psock))
 59		return __unix_recvmsg(sk, msg, len, flags);
 60
 61	mutex_lock(&u->iolock);
 62	if (!skb_queue_empty(&sk->sk_receive_queue) &&
 63	    sk_psock_queue_empty(psock)) {
 64		mutex_unlock(&u->iolock);
 65		sk_psock_put(sk, psock);
 66		return __unix_recvmsg(sk, msg, len, flags);
 67	}
 68
 69msg_bytes_ready:
 70	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
 71	if (!copied) {
 72		long timeo;
 73		int data;
 74
 75		timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 76		data = unix_msg_wait_data(sk, psock, timeo);
 77		if (data) {
 78			if (!sk_psock_queue_empty(psock))
 79				goto msg_bytes_ready;
 80			mutex_unlock(&u->iolock);
 81			sk_psock_put(sk, psock);
 82			return __unix_recvmsg(sk, msg, len, flags);
 83		}
 84		copied = -EAGAIN;
 85	}
 86	mutex_unlock(&u->iolock);
 87	sk_psock_put(sk, psock);
 88	return copied;
 89}
 90
 91static struct proto *unix_dgram_prot_saved __read_mostly;
 92static DEFINE_SPINLOCK(unix_dgram_prot_lock);
 93static struct proto unix_dgram_bpf_prot;
 94
 95static struct proto *unix_stream_prot_saved __read_mostly;
 96static DEFINE_SPINLOCK(unix_stream_prot_lock);
 97static struct proto unix_stream_bpf_prot;
 98
 99static void unix_dgram_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
100{
101	*prot        = *base;
102	prot->close  = sock_map_close;
103	prot->recvmsg = unix_bpf_recvmsg;
104	prot->sock_is_readable = sk_msg_is_readable;
105}
106
107static void unix_stream_bpf_rebuild_protos(struct proto *prot,
108					   const struct proto *base)
109{
110	*prot        = *base;
111	prot->close  = sock_map_close;
112	prot->recvmsg = unix_bpf_recvmsg;
113	prot->sock_is_readable = sk_msg_is_readable;
114	prot->unhash  = sock_map_unhash;
115}
116
117static void unix_dgram_bpf_check_needs_rebuild(struct proto *ops)
118{
119	if (unlikely(ops != smp_load_acquire(&unix_dgram_prot_saved))) {
120		spin_lock_bh(&unix_dgram_prot_lock);
121		if (likely(ops != unix_dgram_prot_saved)) {
122			unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, ops);
123			smp_store_release(&unix_dgram_prot_saved, ops);
124		}
125		spin_unlock_bh(&unix_dgram_prot_lock);
126	}
127}
128
129static void unix_stream_bpf_check_needs_rebuild(struct proto *ops)
130{
131	if (unlikely(ops != smp_load_acquire(&unix_stream_prot_saved))) {
132		spin_lock_bh(&unix_stream_prot_lock);
133		if (likely(ops != unix_stream_prot_saved)) {
134			unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, ops);
135			smp_store_release(&unix_stream_prot_saved, ops);
136		}
137		spin_unlock_bh(&unix_stream_prot_lock);
138	}
139}
140
141int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
142{
143	if (sk->sk_type != SOCK_DGRAM)
144		return -EOPNOTSUPP;
145
146	if (restore) {
147		sk->sk_write_space = psock->saved_write_space;
148		sock_replace_proto(sk, psock->sk_proto);
149		return 0;
150	}
151
152	unix_dgram_bpf_check_needs_rebuild(psock->sk_proto);
153	sock_replace_proto(sk, &unix_dgram_bpf_prot);
154	return 0;
155}
156
157int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
158{
159	if (restore) {
160		sk->sk_write_space = psock->saved_write_space;
161		sock_replace_proto(sk, psock->sk_proto);
162		return 0;
163	}
164
165	unix_stream_bpf_check_needs_rebuild(psock->sk_proto);
166	sock_replace_proto(sk, &unix_stream_bpf_prot);
167	return 0;
168}
169
170void __init unix_bpf_build_proto(void)
171{
172	unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, &unix_dgram_proto);
173	unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, &unix_stream_proto);
174
175}