Debian GNU/Linux 7 syzkaller ttyS0

executing program
syzkaller login: [   47.804527] refcount_t: underflow; use-after-free.
[   47.804988] ------------[ cut here ]------------
[   47.805365] WARNING: CPU: 2 PID: 3014 at lib/refcount.c:186 refcount_sub_and_test+0x167/0x1b0
[   47.806053] Kernel panic - not syncing: panic_on_warn set ...
[   47.806053] 
[   47.806617] CPU: 2 PID: 3014 Comm: syzkaller704351 Not tainted 4.13.0-next-20170905+ #15
[   47.807217] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
[   47.807912] Call Trace:
[   47.808135]  dump_stack+0x194/0x257
[   47.808395]  ? arch_local_irq_restore+0x53/0x53
[   47.808770]  panic+0x1e4/0x417
[   47.808998]  ? __warn+0x1d9/0x1d9
[   47.809315]  ? show_regs_print_info+0x65/0x65
[   47.809739]  ? refcount_sub_and_test+0x167/0x1b0
[   47.810173]  __warn+0x1c4/0x1d9
[   47.810477]  ? refcount_sub_and_test+0x167/0x1b0
[   47.810916]  report_bug+0x211/0x2d0
[   47.811254]  fixup_bug+0x40/0x90
[   47.811567]  do_trap+0x260/0x390
[   47.811908]  do_error_trap+0x120/0x390
[   47.812267]  ? do_trap+0x390/0x390
[   47.812595]  ? refcount_sub_and_test+0x167/0x1b0
[   47.813053]  ? vprintk_emit+0x3ea/0x590
[   47.813427]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[   47.813872]  do_invalid_op+0x1b/0x20
[   47.814217]  invalid_op+0x18/0x20
[   47.814537] RIP: 0010:refcount_sub_and_test+0x167/0x1b0
[   47.815025] RSP: 0018:ffff88003a906300 EFLAGS: 00010282
[   47.815517] RAX: 0000000000000026 RBX: 0000000000000001 RCX: 0000000000000000
[   47.816177] RDX: 0000000000000026 RSI: 1ffff10007520c20 RDI: ffffed0007520c54
[   47.816683] RBP: ffff88003a906390 R08: ffff88003a9059f0 R09: 0000000000000000
[   47.817186] R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff10007520c61
[   47.817690] R13: 00000000ffffff01 R14: 0000000000000100 R15: ffff88003b7f1324
[   47.818207]  ? refcount_inc+0x50/0x50
[   47.818478]  ? __sctp_outq_teardown+0xc7d/0x15a0
[   47.818810]  ? sctp_association_free+0x2d0/0x930
[   47.819145]  ? sctp_do_sm+0x28e7/0x6dd0
[   47.819423]  ? sctp_primitive_SHUTDOWN+0xa0/0xd0
[   47.819754]  ? sctp_close+0x3c6/0x980
[   47.820020]  ? inet_release+0xed/0x1c0
[   47.820296]  sctp_wfree+0x183/0x620
[   47.820554]  ? __sctp_write_space+0x910/0x910
[   47.820875]  skb_release_head_state+0x124/0x200
[   47.821232]  skb_release_all+0x15/0x60
[   47.821837]  consume_skb+0x153/0x490
[   47.822466]  ? sctp_chunk_put+0x99/0x420
[   47.822770]  ? alloc_skb_with_frags+0x710/0x710
[   47.823142]  ? sctp_chunk_hold+0x20/0x20
[   47.823445]  ? refcount_sub_and_test+0x115/0x1b0
[   47.823795]  ? refcount_inc+0x50/0x50
[   47.824077]  ? mark_held_locks+0xb2/0x100
[   47.824391]  ? sctp_datamsg_put+0x456/0x560
[   47.824803]  sctp_chunk_put+0x29c/0x420
[   47.825169]  ? sctp_chunk_hold+0x20/0x20
[   47.825544]  ? sctp_transport_dst_confirm+0x50/0x50
[   47.826013]  sctp_chunk_free+0x53/0x60
[   47.826371]  __sctp_outq_teardown+0xc7d/0x15a0
[   47.826789]  ? inet6_release+0x50/0x70
[   47.827151]  ? sctp_inq_set_th_handler+0x1b0/0x1b0
[   47.827600]  ? unwind_next_frame.part.6+0x1ae/0xc70
[   47.828059]  ? unwind_next_frame.part.6+0x1ae/0xc70
[   47.828513]  ? unwind_dump+0x4c0/0x4c0
[   47.828874]  ? unwind_dump+0x4c0/0x4c0
[   47.829231]  ? copy_trace+0x1d0/0x1d0
[   47.829584]  ? check_noncircular+0x20/0x20
[   47.829971]  ? check_noncircular+0x20/0x20
[   47.830267]  ? unwind_get_return_address+0x61/0xa0
[   47.830614]  ? __save_stack_trace+0x61/0xd0
[   47.831009]  ? check_noncircular+0x20/0x20
[   47.831399]  ? print_usage_bug+0x480/0x480
[   47.831790]  ? find_held_lock+0x39/0x1d0
[   47.832168]  ? lock_downgrade+0x990/0x990
[   47.832553]  ? sk_dst_check+0x560/0x560
[   47.832840]  ? rcu_read_lock_sched_held+0x108/0x120
[   47.833192]  ? lock_release+0xd70/0xd70
[   47.833475]  sctp_outq_free+0x15/0x20
[   47.833741]  sctp_association_free+0x2d0/0x930
[   47.834066]  ? sctp_asconf_queue_teardown+0x700/0x700
[   47.834430]  ? sock_def_wakeup+0x222/0x350
[   47.834728]  ? sk_dst_check+0x560/0x560
[   47.835008]  ? sctp_association_put+0x74/0x2f0
[   47.835326]  ? sctp_association_hold+0x20/0x20
[   47.835651]  ? __unwind_start+0x169/0x330
[   47.835943]  ? sctp_sm_lookup_event+0x95/0x3c0
[   47.836263]  sctp_do_sm+0x28e7/0x6dd0
[   47.836540]  ? sctp_do_8_2_transport_strike.isra.16+0x8a0/0x8a0
[   47.836969]  ? debug_check_no_locks_freed+0x3d0/0x3d0
[   47.837330]  ? print_usage_bug+0x480/0x480
[   47.837632]  ? print_usage_bug+0x480/0x480
[   47.837933]  ? find_held_lock+0x39/0x1d0
[   47.838237]  ? lock_downgrade+0x990/0x990
[   47.838545]  ? skb_dequeue+0x22/0x180
[   47.838817]  ? do_raw_spin_trylock+0x190/0x190
[   47.839136]  ? mark_held_locks+0xb2/0x100
[   47.839430]  ? trace_hardirqs_on+0xd/0x10
[   47.839725]  sctp_primitive_SHUTDOWN+0xa0/0xd0
[   47.840044]  sctp_close+0x3c6/0x980
[   47.840384]  ? sctp_apply_peer_addr_params+0xf30/0xf30
[   47.840782]  ? trace_hardirqs_on_caller+0x421/0x5c0
[   47.841147]  ? trace_hardirqs_on+0xd/0x10
[   47.841480]  ? rcu_eqs_enter_common.constprop.73+0x270/0x270
[   47.841906]  ? ipv6_sock_ac_close+0x2e8/0x3e0
[   47.842240]  ? ipv6_sock_mc_close+0x148/0x1a0
[   47.842566]  ? ipv6_sock_ac_drop+0x580/0x580
[   47.842935]  ? ip_mc_drop_socket+0x1ce/0x230
[   47.843542]  ? __fsnotify_parent+0xb4/0x3a0
[   47.843865]  inet_release+0xed/0x1c0
[   47.844152]  inet6_release+0x50/0x70
[   47.844440]  sock_release+0x8d/0x1e0
[   47.844723]  ? sock_release+0x1e0/0x1e0
[   47.845012]  sock_close+0x16/0x20
[   47.845300]  __fput+0x333/0x7f0
[   47.845557]  ? fput+0x140/0x140
[   47.845801]  ? check_same_owner+0x320/0x320
[   47.846178]  ____fput+0x15/0x20
[   47.846441]  task_work_run+0x199/0x270
[   47.846730]  ? task_work_cancel+0x210/0x210
[   47.847044]  ? free_nsproxy+0x185/0x1f0
[   47.847334]  ? switch_task_namespaces+0xa2/0xc0
[   47.847674]  do_exit+0xa52/0x1b40
[   47.847930]  ? print_usage_bug+0x480/0x480
[   47.848251]  ? mm_update_next_owner+0x930/0x930
[   47.848595]  ? find_held_lock+0x39/0x1d0
[   47.848897]  ? check_noncircular+0x20/0x20
[   47.849266]  ? check_noncircular+0x20/0x20
[   47.849655]  ? lock_downgrade+0x990/0x990
[   47.850044]  ? reacquire_held_locks+0x205/0x3d0
[   47.850473]  ? check_noncircular+0x20/0x20
[   47.850864]  ? find_held_lock+0x39/0x1d0
[   47.851246]  ? lock_downgrade+0x990/0x990
[   47.851629]  ? lock_downgrade+0x990/0x990
[   47.852013]  ? find_held_lock+0x39/0x1d0
[   47.852392]  ? lock_downgrade+0x990/0x990
[   47.852779]  ? recalc_sigpending_tsk+0x117/0x150
[   47.853217]  ? recalc_sigpending+0x103/0x160
[   47.853649]  ? recalc_sigpending_tsk+0x150/0x150
[   47.854111]  ? get_signal+0x397/0x17e0
[   47.854531]  do_group_exit+0x149/0x400
[   47.854886]  ? __lock_is_held+0xbc/0x140
[   47.855260]  ? SyS_exit+0x30/0x30
[   47.855579]  ? _raw_spin_unlock_irq+0x27/0x70
[   47.856019]  ? trace_hardirqs_on_caller+0x421/0x5c0
[   47.856519]  get_signal+0x7e8/0x17e0
[   47.856899]  ? ptrace_notify+0x130/0x130
[   47.857275]  ? __local_bh_enable_ip+0x9d/0x160
[   47.857698]  ? trace_hardirqs_on_caller+0x421/0x5c0
[   47.858158]  ? release_sock+0x1d4/0x2a0
[   47.858524]  ? trace_hardirqs_on+0xd/0x10
[   47.858905]  ? __local_bh_enable_ip+0x9d/0x160
[   47.859351]  ? _raw_spin_unlock_bh+0x30/0x40
[   47.859735]  ? release_sock+0x1d4/0x2a0
[   47.860103]  ? trace_hardirqs_on+0xd/0x10
[   47.860399]  do_signal+0x94/0x1ee0
[   47.860653]  ? inet_sendmsg+0x11f/0x5e0
[   47.860931]  ? inet_sendmsg+0x126/0x5e0
[   47.861209]  ? __might_sleep+0x95/0x190
[   47.861491]  ? setup_sigcontext+0x7d0/0x7d0
[   47.861792]  ? selinux_socket_sendmsg+0x36/0x40
[   47.862118]  ? security_socket_sendmsg+0x89/0xb0
[   47.862450]  ? inet_recvmsg+0x5f0/0x5f0
[   47.862729]  ? sock_sendmsg+0x4f/0x110
[   47.863002]  ? fput+0xd2/0x140
[   47.863225]  ? SYSC_sendto+0x413/0x5a0
[   47.863532]  ? SYSC_connect+0x480/0x480
[   47.863820]  ? exit_to_usermode_loop+0x98/0x300
[   47.864162]  exit_to_usermode_loop+0x224/0x300
[   47.864764]  ? trace_event_raw_event_sys_exit+0x260/0x260
[   47.865149]  ? trace_hardirqs_on_caller+0x421/0x5c0
[   47.865557]  syscall_return_slowpath+0x42f/0x500
[   47.866016]  ? finish_task_switch+0x1aa/0x740
[   47.866429]  ? prepare_exit_to_usermode+0x2c0/0x2c0
[   47.866886]  ? entry_SYSCALL_64_fastpath+0x91/0xbe
[   47.867339]  ? trace_hardirqs_on_caller+0x421/0x5c0
[   47.867795]  ? trace_hardirqs_on_thunk+0x1a/0x1c
[   47.868233]  entry_SYSCALL_64_fastpath+0xbc/0xbe
[   47.868664] RIP: 0033:0x43b279
[   47.868964] RSP: 002b:00007f3929fbfdb8 EFLAGS: 00000206 ORIG_RAX: 000000000000002c
[   47.869663] RAX: 0000000000000001 RBX: 0000000000000000 RCX: 000000000043b279
[   47.870188] RDX: 0000000000000001 RSI: 0000000020a75f25 RDI: 0000000000000003
[   47.870693] RBP: 0000000000000000 R08: 00000000205e4fe4 R09: 000000000000001c
[   47.871222] R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
[   47.871725] R13: 0000000000000000 R14: 00007f3929fc09c0 R15: 00007f3929fc0700
[   47.872412] Dumping ftrace buffer:
[   47.872746]    (ftrace buffer empty)
[   47.873004] Kernel Offset: disabled
[   47.873311] Rebooting in 86400 seconds..