sctp: destroy bucket if failed to bind addr

There is one memory leak bug report:
BUG: memory leak
unreferenced object 0xffff8881dc4c5ec0 (size 40):
  comm "syz-executor.0", pid 5673, jiffies 4298198457 (age 27.578s)
  hex dump (first 32 bytes):
    02 00 00 00 81 88 ff ff 00 00 00 00 00 00 00 00  ................
    f8 63 3d c1 81 88 ff ff 00 00 00 00 00 00 00 00  .c=.............
  backtrace:
    [<0000000072006339>] sctp_get_port_local+0x2a1/0xa00 [sctp]
    [<00000000c7b379ec>] sctp_do_bind+0x176/0x2c0 [sctp]
    [<000000005be274a2>] sctp_bind+0x5a/0x80 [sctp]
    [<00000000b66b4044>] inet6_bind+0x59/0xd0 [ipv6]
    [<00000000c68c7f42>] __sys_bind+0x120/0x1f0 net/socket.c:1647
    [<000000004513635b>] __do_sys_bind net/socket.c:1658 [inline]
    [<000000004513635b>] __se_sys_bind net/socket.c:1656 [inline]
    [<000000004513635b>] __x64_sys_bind+0x3e/0x50 net/socket.c:1656
    [<0000000061f2501e>] do_syscall_64+0x72/0x2e0 arch/x86/entry/common.c:296
    [<0000000003d1e05e>] entry_SYSCALL_64_after_hwframe+0x49/0xbe

This is because in sctp_do_bind, if sctp_get_port_local is to
create hash bucket successfully, and sctp_add_bind_addr failed
to bind address, e.g return -ENOMEM, so memory leak found, it
needs to destroy allocated bucket.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Mao Wenan <maowenan@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -412,11 +412,13 @@ static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
 	ret = sctp_add_bind_addr(bp, addr, af->sockaddr_len,
 				 SCTP_ADDR_SRC, GFP_ATOMIC);
 
+	if (ret) {
+		sctp_put_port(sk);
+		return ret;
+	}
 	/* Copy back into socket for getsockname() use. */
-	if (!ret) {
 	inet_sk(sk)->inet_sport = htons(inet_sk(sk)->inet_num);
 	sp->pf->to_sk_saddr(addr, sk);
-	}
 
 	return ret;
 }