net/sctp: use in_compat_syscall for sctp_getsockopt_connectx3

SCTP unfortunately has a different ABI for SCTP_SOCKOPT_CONNECTX3 for
32-bit and 64-bit callers.  Use in_compat_syscall to correctly
distinguish them on all architectures.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

net/sctp/socket.c

@@ -1389,7 +1389,7 @@ static int sctp_getsockopt_connectx3(struct sock *sk, int len,
 	int err = 0;
 
 #ifdef CONFIG_COMPAT
-	if (is_compat_task()) {
+	if (in_compat_syscall()) {
 		struct compat_sctp_getaddrs_old param32;
 
 		if (len < sizeof(param32))