executing program syzkaller login: [ 20.072608] refcount_t: underflow; use-after-free. [ 20.073220] ------------[ cut here ]------------ [ 20.073899] WARNING: CPU: 0 PID: 2995 at lib/refcount.c:186 refcount_sub_and_test+0x167/0x1b0 [ 20.075269] Kernel panic - not syncing: panic_on_warn set ... [ 20.075269] [ 20.076045] CPU: 0 PID: 2995 Comm: syzkaller492251 Not tainted 4.14.0-rc5-next-20171018+ #8 [ 20.076904] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 20.077880] Call Trace: [ 20.078159] dump_stack+0x194/0x257 [ 20.078551] ? arch_local_irq_restore+0x53/0x53 [ 20.079064] ? vsnprintf+0x1ed/0x1900 [ 20.079503] panic+0x1e4/0x41c [ 20.079839] ? refcount_error_report+0x214/0x214 [ 20.080208] ? show_regs_print_info+0x65/0x65 [ 20.080643] ? __warn+0x1a9/0x1e0 [ 20.080965] ? refcount_sub_and_test+0x167/0x1b0 [ 20.081526] __warn+0x1c4/0x1e0 [ 20.081765] ? refcount_sub_and_test+0x167/0x1b0 [ 20.082113] report_bug+0x211/0x2d0 [ 20.082384] fixup_bug+0x40/0x90 [ 20.082624] do_trap+0x260/0x390 [ 20.082870] do_error_trap+0x120/0x390 [ 20.083161] ? vprintk_emit+0x49b/0x590 [ 20.083451] ? do_trap+0x390/0x390 [ 20.083705] ? refcount_sub_and_test+0x167/0x1b0 [ 20.084042] ? vprintk_emit+0x3ea/0x590 [ 20.084357] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 20.084710] do_invalid_op+0x1b/0x20 [ 20.085029] invalid_op+0x18/0x20 [ 20.085315] RIP: 0010:refcount_sub_and_test+0x167/0x1b0 [ 20.085712] RSP: 0018:ffff8800684e6a38 EFLAGS: 00010282 [ 20.086093] RAX: 0000000000000026 RBX: 0000000000000001 RCX: 0000000000000000 [ 20.086629] RDX: 0000000000000026 RSI: 1ffff1000d09cd07 RDI: ffffed000d09cd3b [ 20.087141] RBP: ffff8800684e6ac8 R08: 0000000000000001 R09: 0000000000000000 [ 20.087650] R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1000d09cd48 [ 20.088172] R13: 00000000ffffff01 R14: 0000000000000100 R15: ffff88003db6ea3c [ 20.088702] ? refcount_sub_and_test+0x167/0x1b0 [ 20.089064] ? refcount_inc+0x50/0x50 [ 20.089339] ? sctp_outq_free+0x15/0x20 [ 20.089734] ? sctp_do_sm+0x271b/0x6a30 [ 20.090058] ? sctp_primitive_SHUTDOWN+0xa0/0xd0 [ 20.090441] ? sctp_close+0x3c6/0x980 [ 20.090709] ? inet_release+0xed/0x1c0 [ 20.091046] ? inet6_release+0x50/0x70 [ 20.091325] sctp_wfree+0x183/0x620 [ 20.091560] ? __sctp_write_space+0x910/0x910 [ 20.091868] skb_release_head_state+0x124/0x200 [ 20.092300] skb_release_all+0x15/0x60 [ 20.092709] consume_skb+0x153/0x490 [ 20.093095] ? sctp_chunk_put+0x99/0x420 [ 20.093527] ? alloc_skb_with_frags+0x750/0x750 [ 20.094004] ? sctp_chunk_hold+0x20/0x20 [ 20.094427] ? refcount_sub_and_test+0x115/0x1b0 [ 20.094915] ? refcount_inc+0x50/0x50 [ 20.095271] ? mark_held_locks+0xaf/0x100 [ 20.095652] ? sctp_datamsg_put+0x456/0x560 [ 20.096041] sctp_chunk_put+0x29c/0x420 [ 20.096372] ? sctp_chunk_hold+0x20/0x20 [ 20.096676] ? sctp_transport_dst_confirm+0x50/0x50 [ 20.097046] ? sctp_sched_fcfs_dequeue+0x198/0x290 [ 20.097740] ? sctp_sched_dequeue_common+0x5d0/0x5d0 [ 20.098138] sctp_chunk_free+0x53/0x60 [ 20.098427] __sctp_outq_teardown+0xa5b/0x1230 [ 20.098775] ? sctp_inq_set_th_handler+0x1b0/0x1b0 [ 20.099142] ? __kernel_text_address+0xd/0x40 [ 20.099474] ? unwind_get_return_address+0x61/0xa0 [ 20.099837] ? __save_stack_trace+0x7e/0xd0 [ 20.100167] ? add_lock_to_list.isra.32+0x292/0x39b [ 20.100542] ? check_noncircular+0x20/0x20 [ 20.100855] ? print_irqtrace_events+0x270/0x270 [ 20.101220] ? lock_acquire+0x1d5/0x580 [ 20.102063] ? lock_acquire+0x1d5/0x580 [ 20.102414] ? lock_timer_base+0x1a3/0x2b0 [ 20.102792] ? find_held_lock+0x35/0x1d0 [ 20.103159] ? sock_def_wakeup+0x1f9/0x350 [ 20.103541] ? lock_downgrade+0x990/0x990 [ 20.103930] ? lock_release+0xa40/0xa40 [ 20.104292] sctp_outq_free+0x15/0x20 [ 20.104638] sctp_association_free+0x2d0/0x930 [ 20.105227] ? sctp_asconf_queue_teardown+0x700/0x700 [ 20.105769] ? sock_def_wakeup+0x222/0x350 [ 20.106198] ? sk_dst_check+0x560/0x560 [ 20.106613] ? sctp_association_put+0x74/0x2f0 [ 20.107072] ? sctp_association_hold+0x20/0x20 [ 20.107664] sctp_do_sm+0x271b/0x6a30 [ 20.108069] ? sctp_do_8_2_transport_strike.isra.16+0x8a0/0x8a0 [ 20.108717] ? __free_insn_slot+0x5c0/0x5c0 [ 20.109179] ? print_irqtrace_events+0x270/0x270 [ 20.109690] ? print_irqtrace_events+0x270/0x270 [ 20.110237] ? find_held_lock+0x35/0x1d0 [ 20.110701] ? skb_dequeue+0x12a/0x180 [ 20.111154] ? lock_downgrade+0x990/0x990 [ 20.111607] ? do_raw_spin_trylock+0x190/0x190 [ 20.112101] ? mark_held_locks+0xaf/0x100 [ 20.112564] ? trace_hardirqs_on+0xd/0x10 [ 20.113044] sctp_primitive_SHUTDOWN+0xa0/0xd0 [ 20.113630] sctp_close+0x3c6/0x980 [ 20.114017] ? sctp_apply_peer_addr_params+0xf30/0xf30 [ 20.114517] ? unwind_get_return_address+0x61/0xa0 [ 20.114991] ? __save_stack_trace+0x7e/0xd0 [ 20.115449] ? check_noncircular+0x20/0x20 [ 20.115832] ? check_noncircular+0x20/0x20 [ 20.116147] ? ipv6_sock_ac_close+0x2e8/0x3e0 [ 20.116512] ? ipv6_sock_mc_close+0x148/0x1a0 [ 20.116934] ? ip_mc_drop_socket+0x1ce/0x230 [ 20.117355] ? __fsnotify_parent+0xb4/0x3a0 [ 20.117780] inet_release+0xed/0x1c0 [ 20.118136] inet6_release+0x50/0x70 [ 20.118487] sock_release+0x8d/0x1e0 [ 20.118843] ? sock_release+0x1e0/0x1e0 [ 20.119237] sock_close+0x16/0x20 [ 20.119574] __fput+0x327/0x7e0 [ 20.119887] ? fput+0x140/0x140 [ 20.120199] ? _raw_spin_unlock_irq+0x27/0x70 [ 20.120629] ____fput+0x15/0x20 [ 20.120938] task_work_run+0x199/0x270 [ 20.121293] ? task_work_cancel+0x210/0x210 [ 20.121706] ? _raw_spin_unlock+0x22/0x30 [ 20.122107] ? switch_task_namespaces+0x87/0xc0 [ 20.122551] do_exit+0x9b5/0x1ad0 [ 20.122919] ? __fd_install+0x2da/0x6a0 [ 20.123302] ? mm_update_next_owner+0x930/0x930 [ 20.123771] ? __lock_is_held+0xb6/0x140 [ 20.124168] ? __fd_install+0x2f7/0x6a0 [ 20.124554] ? get_unused_fd_flags+0x190/0x190 [ 20.124986] ? __might_sleep+0x95/0x190 [ 20.125368] ? kasan_check_read+0x11/0x20 [ 20.125752] ? _copy_to_user+0xa2/0xc0 [ 20.126122] ? fd_install+0x4d/0x60 [ 20.126464] ? SYSC_accept4+0x4ec/0x850 [ 20.126831] ? __release_sock+0x360/0x360 [ 20.127227] ? kernel_accept+0x2f0/0x2f0 [ 20.127611] ? sctp_inet_listen+0x141/0x850 [ 20.128020] ? sctp_transport_get_idx+0x70/0x70 [ 20.128442] ? selinux_socket_listen+0x36/0x40 [ 20.128721] ? security_socket_listen+0x81/0xb0 [ 20.129020] do_group_exit+0x149/0x400 [ 20.129277] ? SyS_bind+0x30/0x30 [ 20.129589] ? SyS_exit+0x30/0x30 [ 20.129800] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 20.130158] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 20.130463] SyS_exit_group+0x1d/0x20 [ 20.130751] entry_SYSCALL_64_fastpath+0x1f/0xbe [ 20.131144] RIP: 0033:0x433a89 [ 20.131385] RSP: 002b:00007ffc1a29e8c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 20.131866] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000433a89 [ 20.132362] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 20.132877] RBP: 0000000000000082 R08: 000000000000003c R09: 00000000000000e7 [ 20.133597] R10: ffffffffffffffc0 R11: 0000000000000246 R12: 0000000000000000 [ 20.134267] R13: 00000000004018c0 R14: 0000000000401950 R15: 0000000000000000 [ 20.135112] Dumping ftrace buffer: [ 20.135543] (ftrace buffer empty) [ 20.135891] Kernel Offset: disabled [ 20.136235] Rebooting in 86400 seconds..