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 nonblock, int flags,
  52                             int *addr_len)
  53 {
  54         struct unix_sock *u = unix_sk(sk);
  55         struct sk_psock *psock;
  56         int copied;
  57
  58         if (!len)
  59                 return 0;
  60
  61         psock = sk_psock_get(sk);
  62         if (unlikely(!psock))
  63                 return __unix_recvmsg(sk, msg, len, flags);
  64
  65         mutex_lock(&u->iolock);
  66         if (!skb_queue_empty(&sk->sk_receive_queue) &&
  67             sk_psock_queue_empty(psock)) {
  68                 mutex_unlock(&u->iolock);
  69                 sk_psock_put(sk, psock);
  70                 return __unix_recvmsg(sk, msg, len, flags);
  71         }
  72
  73 msg_bytes_ready:
  74         copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
  75         if (!copied) {
  76                 long timeo;
  77                 int data;
  78
  79                 timeo = sock_rcvtimeo(sk, nonblock);
  80                 data = unix_msg_wait_data(sk, psock, timeo);
  81                 if (data) {
  82                         if (!sk_psock_queue_empty(psock))
  83                                 goto msg_bytes_ready;
  84                         mutex_unlock(&u->iolock);
  85                         sk_psock_put(sk, psock);
  86                         return __unix_recvmsg(sk, msg, len, flags);
  87                 }
  88                 copied = -EAGAIN;
  89         }
  90         mutex_unlock(&u->iolock);
  91         sk_psock_put(sk, psock);
  92         return copied;
  93 }
  94
  95 static struct proto *unix_dgram_prot_saved __read_mostly;
  96 static DEFINE_SPINLOCK(unix_dgram_prot_lock);
  97 static struct proto unix_dgram_bpf_prot;
  98
  99 static struct proto *unix_stream_prot_saved __read_mostly;
 100 static DEFINE_SPINLOCK(unix_stream_prot_lock);
 101 static struct proto unix_stream_bpf_prot;
 102
 103 static void unix_dgram_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
 104 {
 105         *prot        = *base;
 106         prot->close  = sock_map_close;
 107         prot->recvmsg = unix_bpf_recvmsg;
 108         prot->sock_is_readable = sk_msg_is_readable;
 109 }
 110
 111 static void unix_stream_bpf_rebuild_protos(struct proto *prot,
 112                                            const struct proto *base)
 113 {
 114         *prot        = *base;
 115         prot->close  = sock_map_close;
 116         prot->recvmsg = unix_bpf_recvmsg;
 117         prot->sock_is_readable = sk_msg_is_readable;
 118         prot->unhash  = sock_map_unhash;
 119 }
 120
 121 static void unix_dgram_bpf_check_needs_rebuild(struct proto *ops)
 122 {
 123         if (unlikely(ops != smp_load_acquire(&unix_dgram_prot_saved))) {
 124                 spin_lock_bh(&unix_dgram_prot_lock);
 125                 if (likely(ops != unix_dgram_prot_saved)) {
 126                         unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, ops);
 127                         smp_store_release(&unix_dgram_prot_saved, ops);
 128                 }
 129                 spin_unlock_bh(&unix_dgram_prot_lock);
 130         }
 131 }
 132
 133 static void unix_stream_bpf_check_needs_rebuild(struct proto *ops)
 134 {
 135         if (unlikely(ops != smp_load_acquire(&unix_stream_prot_saved))) {
 136                 spin_lock_bh(&unix_stream_prot_lock);
 137                 if (likely(ops != unix_stream_prot_saved)) {
 138                         unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, ops);
 139                         smp_store_release(&unix_stream_prot_saved, ops);
 140                 }
 141                 spin_unlock_bh(&unix_stream_prot_lock);
 142         }
 143 }
 144
 145 int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
 146 {
 147         if (sk->sk_type != SOCK_DGRAM)
 148                 return -EOPNOTSUPP;
 149
 150         if (restore) {
 151                 sk->sk_write_space = psock->saved_write_space;
 152                 WRITE_ONCE(sk->sk_prot, psock->sk_proto);
 153                 return 0;
 154         }
 155
 156         unix_dgram_bpf_check_needs_rebuild(psock->sk_proto);
 157         WRITE_ONCE(sk->sk_prot, &unix_dgram_bpf_prot);
 158         return 0;
 159 }
 160
 161 int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
 162 {
 163         if (restore) {
 164                 sk->sk_write_space = psock->saved_write_space;
 165                 WRITE_ONCE(sk->sk_prot, psock->sk_proto);
 166                 return 0;
 167         }
 168
 169         unix_stream_bpf_check_needs_rebuild(psock->sk_proto);
 170         WRITE_ONCE(sk->sk_prot, &unix_stream_bpf_prot);
 171         return 0;
 172 }
 173
 174 void __init unix_bpf_build_proto(void)
 175 {
 176         unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, &unix_dgram_proto);
 177         unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, &unix_stream_proto);
 178
 179 }