If IPv6 support is disabled at boot (ipv6.disable=1),
the calipso_init() -> netlbl_calipso_ops_register() function isn't called,
and the netlbl_calipso_ops_get() function always returns NULL.
In this case, the netlbl_calipso_add_pass() function allocates memory
for the doi_def variable but doesn't free it with the calipso_doi_free().

BUG: memory leak
unreferenced object 0xffff888011d68180 (size 64):
  comm "syz-executor.1", pid 10746, jiffies 4295410986 (age 17.928s)
  hex dump (first 32 bytes):
    00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<...>] kmalloc include/linux/slab.h:552 [inline]
    [<...>] netlbl_calipso_add_pass net/netlabel/netlabel_calipso.c:76 [inline]
    [<...>] netlbl_calipso_add+0x22e/0x4f0 net/netlabel/netlabel_calipso.c:111
    [<...>] genl_family_rcv_msg_doit+0x22f/0x330 net/netlink/genetlink.c:739
    [<...>] genl_family_rcv_msg net/netlink/genetlink.c:783 [inline]
    [<...>] genl_rcv_msg+0x341/0x5a0 net/netlink/genetlink.c:800
    [<...>] netlink_rcv_skb+0x14d/0x440 net/netlink/af_netlink.c:2515
    [<...>] genl_rcv+0x29/0x40 net/netlink/genetlink.c:811
    [<...>] netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
    [<...>] netlink_unicast+0x54b/0x800 net/netlink/af_netlink.c:1339
    [<...>] netlink_sendmsg+0x90a/0xdf0 net/netlink/af_netlink.c:1934
    [<...>] sock_sendmsg_nosec net/socket.c:651 [inline]
    [<...>] sock_sendmsg+0x157/0x190 net/socket.c:671
    [<...>] ____sys_sendmsg+0x712/0x870 net/socket.c:2342
    [<...>] ___sys_sendmsg+0xf8/0x170 net/socket.c:2396
    [<...>] __sys_sendmsg+0xea/0x1b0 net/socket.c:2429
    [<...>] do_syscall_64+0x30/0x40 arch/x86/entry/common.c:46
    [<...>] entry_SYSCALL_64_after_hwframe+0x61/0xc6

Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with Syzkaller

Fixes: cb72d382 ("netlabel: Initial support for the CALIPSO netlink protocol.")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru>
[PM: merged via the LSM tree at Jakub Kicinski request]
Signed-off-by: Paul Moore <paul@paul-moore.com>