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