net/unix/unix_bpf.c

   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         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
  69 msg_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
  91 static struct proto *unix_dgram_prot_saved __read_mostly;
  92 static DEFINE_SPINLOCK(unix_dgram_prot_lock);
  93 static struct proto unix_dgram_bpf_prot;
  94
  95 static struct proto *unix_stream_prot_saved __read_mostly;
  96 static DEFINE_SPINLOCK(unix_stream_prot_lock);
  97 static struct proto unix_stream_bpf_prot;
  98
  99 static 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
 107 static 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
 117 static 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
 129 static 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
 141 int 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                 WRITE_ONCE(sk->sk_prot, psock->sk_proto);
 149                 return 0;
 150         }
 151
 152         unix_dgram_bpf_check_needs_rebuild(psock->sk_proto);
 153         WRITE_ONCE(sk->sk_prot, &unix_dgram_bpf_prot);
 154         return 0;
 155 }
 156
 157 int 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                 WRITE_ONCE(sk->sk_prot, psock->sk_proto);
 162                 return 0;
 163         }
 164
 165         unix_stream_bpf_check_needs_rebuild(psock->sk_proto);
 166         WRITE_ONCE(sk->sk_prot, &unix_stream_bpf_prot);
 167         return 0;
 168 }
 169
 170 void __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 }