refcount_t: underflow; use-after-free.
------------[ cut here ]------------
WARNING: CPU: 1 PID: 20099 at lib/refcount.c:187 refcount_sub_and_test lib/refcount.c:187 [inline]
WARNING: CPU: 1 PID: 20099 at lib/refcount.c:187 refcount_sub_and_test.cold+0x18/0x22 lib/refcount.c:177
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 20099 Comm: syz-executor.1 Not tainted 4.14.155-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x142/0x197 lib/dump_stack.c:58
 panic+0x1f9/0x42d kernel/panic.c:183
 __warn.cold+0x2f/0x2f kernel/panic.c:547
 report_bug+0x216/0x254 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:177 [inline]
 fixup_bug arch/x86/kernel/traps.c:172 [inline]
 do_error_trap+0x1bb/0x310 arch/x86/kernel/traps.c:295
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:963
RIP: 0010:refcount_sub_and_test lib/refcount.c:187 [inline]
RIP: 0010:refcount_sub_and_test.cold+0x18/0x22 lib/refcount.c:177
RSP: 0018:ffff88808fcd7730 EFLAGS: 00010282
RAX: 0000000000000026 RBX: 0000000000008001 RCX: 0000000000000000
nla_parse: 17 callbacks suppressed
netlink: 100 bytes leftover after parsing attributes in process `syz-executor.3'.
RDX: 0000000000000000 RSI: ffffffff869d1e80 RDI: ffffed1011f9aedc
RBP: ffff88808fcd7758 R08: 0000000000000026 R09: ffff888042f6ea48
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880508682bc
R13: 0000000000008100 R14: 00000000ffffff01 R15: ffffffff88152e60
 sock_wfree+0xa7/0x160 net/core/sock.c:1812
 sctp_wfree+0x2a1/0x620 net/sctp/socket.c:7829
 skb_release_head_state+0x124/0x260 net/core/skbuff.c:616
 skb_release_all+0x16/0x60 net/core/skbuff.c:629
 __kfree_skb net/core/skbuff.c:645 [inline]
 consume_skb+0xaf/0x340 net/core/skbuff.c:705
 sctp_chunk_destroy net/sctp/sm_make_chunk.c:1442 [inline]
 sctp_chunk_put+0x179/0x270 net/sctp/sm_make_chunk.c:1469
 sctp_chunk_free+0x56/0x70 net/sctp/sm_make_chunk.c:1456
 __sctp_outq_teardown+0x1c2/0xde0 net/sctp/outqueue.c:228
 sctp_outq_free+0x16/0x20 net/sctp/outqueue.c:284
 sctp_association_free+0x1ee/0x753 net/sctp/associola.c:357
 sctp_cmd_delete_tcb net/sctp/sm_sideeffect.c:924 [inline]
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1312 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1179 [inline]
 sctp_do_sm+0x3469/0x4ae0 net/sctp/sm_sideeffect.c:1150
 sctp_primitive_ABORT+0xa0/0xd0 net/sctp/primitive.c:119
 sctp_close+0x25e/0x730 net/sctp/socket.c:1560
 inet_release+0xec/0x1c0 net/ipv4/af_inet.c:425
 __sock_release+0xce/0x2b0 net/socket.c:602
 sock_close+0x1b/0x30 net/socket.c:1139
 __fput+0x275/0x7a0 fs/file_table.c:210
 ____fput+0x16/0x20 fs/file_table.c:244
 task_work_run+0x114/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4bc/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4141d1
RSP: 002b:00007ffe2fb02780 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000009 RCX: 00000000004141d1
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 0000000000000001 R08: 00000000ccd42ff8 R09: ffffffffffffffff
R10: 00007ffe2fb02860 R11: 0000000000000293 R12: 000000000075bf20
R13: 0000000000096ef0 R14: 0000000000760c10 R15: 000000000075bf2c
Kernel Offset: disabled
Rebooting in 86400 seconds..