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sctp: cancel a blocking accept when shutdown a listen socket

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As David Laight noticed,

"In a multithreaded program it is reasonable to have a thread blocked in
 accept(). With TCP a subsequent shutdown(listen_fd, SHUT_RDWR) causes
 the accept to fail. But nothing happens for SCTP."

sctp_disconnect() is eventually called when shutdown a listen socket,
but nothing is done in this function. This patch sets RCV_SHUTDOWN
flag in sk->sk_shutdown there, and adds the check (sk->sk_shutdown &
RCV_SHUTDOWN) to break and return in sctp_accept().

Note that shutdown() is only supported on TCP-style SCTP socket.

Reported-by: David Laight <David.Laight@aculab.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Long 2024-07-01 13:48:49 -04:00 committed by David S. Miller
parent 2e3ed20c17
commit cda91d5b91
1 changed files with 10 additions and 4 deletions
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14
net/sctp/socket.c
View file

@ -4834,10 +4834,14 @@ int sctp_inet_connect(struct socket *sock, struct sockaddr *uaddr,
return sctp_connect(sock->sk, uaddr, addr_len, flags);
}
/* FIXME: Write comments. */
/* Only called when shutdown a listening SCTP socket. */
static int sctp_disconnect(struct sock *sk, int flags)
{
return -EOPNOTSUPP; /* STUB */
if (!sctp_style(sk, TCP))
return -EOPNOTSUPP;
sk->sk_shutdown |= RCV_SHUTDOWN;
return 0;
}
/* 4.1.4 accept() - TCP Style Syntax
@ -4866,7 +4870,8 @@ static struct sock *sctp_accept(struct sock *sk, struct proto_accept_arg *arg)
goto out;
}
if (!sctp_sstate(sk, LISTENING)) {
if (!sctp_sstate(sk, LISTENING) ||
(sk->sk_shutdown & RCV_SHUTDOWN)) {
error = -EINVAL;
goto out;
}
@ -9393,7 +9398,8 @@ static int sctp_wait_for_accept(struct sock *sk, long timeo)
}
err = -EINVAL;
if (!sctp_sstate(sk, LISTENING))
if (!sctp_sstate(sk, LISTENING) ||
(sk->sk_shutdown & RCV_SHUTDOWN))
break;
err = 0;