------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 8354 at lib/refcount.c:187 refcount_sub_and_test_checked+0x2c9/0x310 lib/refcount.c:187 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 8354 Comm: syz-executor4 Not tainted 4.20.0-rc3+ #317 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 panic+0x2ad/0x55c kernel/panic.c:188 __warn.cold.8+0x20/0x45 kernel/panic.c:540 report_bug+0x254/0x2d0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969 RIP: 0010:refcount_sub_and_test_checked+0x2c9/0x310 lib/refcount.c:187 Code: 89 de e8 9a eb ec fd 84 db 74 07 31 db e9 4d ff ff ff e8 ba ea ec fd 48 c7 c7 60 b8 60 88 c6 05 e8 43 80 06 01 e8 07 4b b6 fd <0f> 0b 31 db e9 2c ff ff ff 48 89 cf e8 36 6b 30 fe e9 41 fe ff ff RSP: 0018:ffff8881daf06000 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000100 RSI: ffffffff8165eae5 RDI: 0000000000000005 RBP: ffff8881daf060e8 R08: ffff88818dc323c0 R09: ffffed103b5e3ef8 R10: ffffed103b5e3ef8 R11: ffff8881daf1f7c7 R12: ffff8881c5dc5a3c R13: 00000000ffffea01 R14: ffff8881daf060c0 R15: ffff888180e23840 sock_wfree+0xb8/0x180 net/core/sock.c:1821 sctp_wfree+0x3a8/0xb40 net/sctp/socket.c:8586 skb_release_head_state+0x15f/0x2e0 net/core/skbuff.c:612 skb_release_all+0x15/0x60 net/core/skbuff.c:625 __kfree_skb net/core/skbuff.c:641 [inline] consume_skb+0x1ae/0x570 net/core/skbuff.c:701 sctp_chunk_destroy net/sctp/sm_make_chunk.c:1462 [inline] sctp_chunk_put+0x2d4/0x450 net/sctp/sm_make_chunk.c:1489 sctp_datamsg_destroy net/sctp/chunk.c:128 [inline] sctp_datamsg_put+0x28b/0x620 net/sctp/chunk.c:145 sctp_chunk_free+0x46/0x60 net/sctp/sm_make_chunk.c:1474 __sctp_outq_teardown+0xa8e/0x11f0 net/sctp/outqueue.c:271 kobject: 'loop2' (00000000732979c1): kobject_uevent_env sctp_outq_free+0x15/0x20 net/sctp/outqueue.c:291 kobject: 'loop2' (00000000732979c1): fill_kobj_path: path = '/devices/virtual/block/loop2' sctp_association_free+0x2f0/0x972 net/sctp/associola.c:361 sctp_cmd_delete_tcb net/sctp/sm_sideeffect.c:939 [inline] sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1353 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline] sctp_do_sm+0x4a32/0x7180 net/sctp/sm_sideeffect.c:1191 kobject: 'loop5' (00000000adb876cf): kobject_uevent_env kobject: 'loop5' (00000000adb876cf): fill_kobj_path: path = '/devices/virtual/block/loop5' sctp_assoc_bh_rcv+0x346/0x670 net/sctp/associola.c:1073 sctp_inq_push+0x280/0x370 net/sctp/inqueue.c:95 sctp_rcv+0x2e50/0x4170 net/sctp/input.c:271 sctp6_rcv+0x15/0x30 net/sctp/ipv6.c:1064 ip6_protocol_deliver_rcu+0x381/0x1950 net/ipv6/ip6_input.c:394 ip6_input_finish+0x84/0x170 net/ipv6/ip6_input.c:434 NF_HOOK include/linux/netfilter.h:289 [inline] ip6_input+0xe9/0x600 net/ipv6/ip6_input.c:443 dst_input include/net/dst.h:450 [inline] ip6_rcv_finish+0x17a/0x330 net/ipv6/ip6_input.c:76 NF_HOOK include/linux/netfilter.h:289 [inline] ipv6_rcv+0x115/0x640 net/ipv6/ip6_input.c:272 __netif_receive_skb_one_core+0x14d/0x200 net/core/dev.c:4948 __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:5058 process_backlog+0x24e/0x7a0 net/core/dev.c:5870 napi_poll net/core/dev.c:6293 [inline] net_rx_action+0x7fa/0x19b0 net/core/dev.c:6359 __do_softirq+0x308/0xb7e kernel/softirq.c:292 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1023 do_softirq.part.14+0x126/0x160 kernel/softirq.c:337 do_softirq kernel/softirq.c:329 [inline] __local_bh_enable_ip+0x21d/0x260 kernel/softirq.c:189 local_bh_enable include/linux/bottom_half.h:32 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:696 [inline] ip6_finish_output2+0xce4/0x27a0 net/ipv6/ip6_output.c:121 ip6_finish_output+0x58c/0xc60 net/ipv6/ip6_output.c:154 NF_HOOK_COND include/linux/netfilter.h:278 [inline] ip6_output+0x232/0x9d0 net/ipv6/ip6_output.c:171 dst_output include/net/dst.h:444 [inline] NF_HOOK include/linux/netfilter.h:289 [inline] ip6_xmit+0xf69/0x23e0 net/ipv6/ip6_output.c:275 sctp_v6_xmit+0x385/0x760 net/sctp/ipv6.c:233 sctp_packet_transmit+0x1f16/0x3ca0 net/sctp/output.c:640 sctp_outq_flush_transports net/sctp/outqueue.c:1161 [inline] sctp_outq_flush+0x610/0x34f0 net/sctp/outqueue.c:1209 sctp_outq_uncork+0x6a/0x80 net/sctp/outqueue.c:772 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1349 [inline] sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline] sctp_do_sm+0x4f1c/0x7180 net/sctp/sm_sideeffect.c:1191 sctp_primitive_ABORT+0xa0/0xd0 net/sctp/primitive.c:119 sctp_close+0x278/0xad0 net/sctp/socket.c:1540 inet_release+0x104/0x1f0 net/ipv4/af_inet.c:428 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:458 __sock_release+0xd7/0x250 net/socket.c:579 sock_close+0x19/0x20 net/socket.c:1141 __fput+0x385/0xa30 fs/file_table.c:278 ____fput+0x15/0x20 fs/file_table.c:309 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x411021 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 34 19 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 RSP: 002b:00007fffcf481280 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000411021 RDX: 0000000000000000 RSI: 0000000000730740 RDI: 0000000000000006 RBP: 0000000000000000 R08: 00000000f6d80eab R09: 0000000000000000 R10: 00007fffcf4811b0 R11: 0000000000000293 R12: 0000000000000000 R13: 0000000000000001 R14: 0000000000000461 R15: 0000000000000004 Kernel Offset: disabled Rebooting in 86400 seconds..