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