Commit 9825d866 authored by Cong Wang's avatar Cong Wang Committed by Alexei Starovoitov
Browse files

af_unix: Implement unix_dgram_bpf_recvmsg() 



We have to implement unix_dgram_bpf_recvmsg() to replace the
original ->recvmsg() to retrieve skmsg from ingress_msg.

AF_UNIX is again special here because the lack of
sk_prot->recvmsg(). I simply add a special case inside
unix_dgram_recvmsg() to call sk->sk_prot->recvmsg() directly.

Signed-off-by: default avatarCong Wang <cong.wang@bytedance.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210704190252.11866-8-xiyou.wangcong@gmail.com
parent c6382918

include/net/af_unix.h

+2 −0
Original line number Diff line number Diff line
@@ -82,6 +82,8 @@ static inline struct unix_sock *unix_sk(const struct sock *sk) 
long unix_inq_len(struct sock *sk);

long unix_outq_len(struct sock *sk);



int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,

			 int flags);

#ifdef CONFIG_SYSCTL

int unix_sysctl_register(struct net *net);

void unix_sysctl_unregister(struct net *net);

net/unix/af_unix.c

+16 −3
Original line number Diff line number Diff line
@@ -2098,11 +2098,11 @@ static void unix_copy_addr(struct msghdr *msg, struct sock *sk) 
	}

}



static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg,

			      size_t size, int flags)

int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,

			 int flags)

{

	struct scm_cookie scm;

	struct sock *sk = sock->sk;

	struct socket *sock = sk->sk_socket;

	struct unix_sock *u = unix_sk(sk);

	struct sk_buff *skb, *last;

	long timeo;
@@ -2205,6 +2205,19 @@ static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg, 
	return err;

}



static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,

			      int flags)

{

	struct sock *sk = sock->sk;



#ifdef CONFIG_BPF_SYSCALL

	if (sk->sk_prot != &unix_proto)

		return sk->sk_prot->recvmsg(sk, msg, size, flags & MSG_DONTWAIT,

					    flags & ~MSG_DONTWAIT, NULL);

#endif

	return __unix_dgram_recvmsg(sk, msg, size, flags);

}



static int unix_read_sock(struct sock *sk, read_descriptor_t *desc,

			  sk_read_actor_t recv_actor)

{

net/unix/unix_bpf.c

+75 −0
Original line number Diff line number Diff line
@@ -6,6 +6,80 @@ 
#include <net/sock.h>

#include <net/af_unix.h>



#define unix_sk_has_data(__sk, __psock)					\

		({	!skb_queue_empty(&__sk->sk_receive_queue) ||	\

			!skb_queue_empty(&__psock->ingress_skb) ||	\

			!list_empty(&__psock->ingress_msg);		\

		})



static int unix_msg_wait_data(struct sock *sk, struct sk_psock *psock,

			      long timeo)

{

	DEFINE_WAIT_FUNC(wait, woken_wake_function);

	struct unix_sock *u = unix_sk(sk);

	int ret = 0;



	if (sk->sk_shutdown & RCV_SHUTDOWN)

		return 1;



	if (!timeo)

		return ret;



	add_wait_queue(sk_sleep(sk), &wait);

	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);

	if (!unix_sk_has_data(sk, psock)) {

		mutex_unlock(&u->iolock);

		wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);

		mutex_lock(&u->iolock);

		ret = unix_sk_has_data(sk, psock);

	}

	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);

	remove_wait_queue(sk_sleep(sk), &wait);

	return ret;

}



static int unix_dgram_bpf_recvmsg(struct sock *sk, struct msghdr *msg,

				  size_t len, int nonblock, int flags,

				  int *addr_len)

{

	struct unix_sock *u = unix_sk(sk);

	struct sk_psock *psock;

	int copied, ret;



	psock = sk_psock_get(sk);

	if (unlikely(!psock))

		return __unix_dgram_recvmsg(sk, msg, len, flags);



	mutex_lock(&u->iolock);

	if (!skb_queue_empty(&sk->sk_receive_queue) &&

	    sk_psock_queue_empty(psock)) {

		ret = __unix_dgram_recvmsg(sk, msg, len, flags);

		goto out;

	}



msg_bytes_ready:

	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);

	if (!copied) {

		long timeo;

		int data;



		timeo = sock_rcvtimeo(sk, nonblock);

		data = unix_msg_wait_data(sk, psock, timeo);

		if (data) {

			if (!sk_psock_queue_empty(psock))

				goto msg_bytes_ready;

			ret = __unix_dgram_recvmsg(sk, msg, len, flags);

			goto out;

		}

		copied = -EAGAIN;

	}

	ret = copied;

out:

	mutex_unlock(&u->iolock);

	sk_psock_put(sk, psock);

	return ret;

}



static struct proto *unix_prot_saved __read_mostly;

static DEFINE_SPINLOCK(unix_prot_lock);

static struct proto unix_bpf_prot;
@@ -14,6 +88,7 @@ static void unix_bpf_rebuild_protos(struct proto *prot, const struct proto *base 
{

	*prot        = *base;

	prot->close  = sock_map_close;

	prot->recvmsg = unix_dgram_bpf_recvmsg;

}



static void unix_bpf_check_needs_rebuild(struct proto *ops)