SCTP: Check to make sure file is valid before setting timeout

In-kernel sockets created with sock_create_kern don't usually
have a file and file descriptor allocated to them.  As a result,
when SCTP tries to check the non-blocking flag, we Oops when
dereferencing a NULL file pointer.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -980,6 +980,7 @@ static int __sctp_connect(struct sock* sk,
 	union sctp_addr *sa_addr;
 	void *addr_buf;
 	unsigned short port;
+	unsigned int f_flags = 0;
 
 	sp = sctp_sk(sk);
 	ep = sp->ep;
@@ -1106,7 +1107,14 @@ static int __sctp_connect(struct sock* sk,
 	af->to_sk_daddr(&to, sk);
 	sk->sk_err = 0;
 
-	timeo = sock_sndtimeo(sk, sk->sk_socket->file->f_flags & O_NONBLOCK);
+	/* in-kernel sockets don't generally have a file allocated to them
+	 * if all they do is call sock_create_kern().
+	 */
+	if (sk->sk_socket->file)
+		f_flags = sk->sk_socket->file->f_flags;
+
+	timeo = sock_sndtimeo(sk, f_flags & O_NONBLOCK);
+
 	err = sctp_wait_for_connect(asoc, &timeo);
 
 	/* Don't free association on exit. */