executing program syzkaller login: [ 22.015557] refcount_t: underflow; use-after-free. [ 22.016086] ------------[ cut here ]------------ [ 22.016429] WARNING: CPU: 0 PID: 3030 at lib/refcount.c:186 refcount_sub_and_test+0x167/0x1b0 [ 22.017431] Kernel panic - not syncing: panic_on_warn set ... [ 22.017431] [ 22.018097] CPU: 0 PID: 3030 Comm: syzkaller919576 Not tainted 4.13.0-rc6-next-20170825+ #9 [ 22.018822] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 22.019536] Call Trace: [ 22.019770] dump_stack+0x194/0x257 [ 22.020099] ? arch_local_irq_restore+0x53/0x53 [ 22.020484] panic+0x1e4/0x41c [ 22.020746] ? refcount_error_report+0x214/0x214 [ 22.021165] ? show_regs_print_info+0x65/0x65 [ 22.021575] ? refcount_sub_and_test+0x167/0x1b0 [ 22.021999] __warn+0x1c4/0x1e0 [ 22.022294] ? refcount_sub_and_test+0x167/0x1b0 [ 22.022624] report_bug+0x211/0x2d0 [ 22.022882] fixup_bug+0x40/0x90 [ 22.023117] do_trap+0x260/0x390 [ 22.023359] do_error_trap+0x120/0x390 [ 22.023697] ? do_trap+0x390/0x390 [ 22.023957] ? refcount_sub_and_test+0x167/0x1b0 [ 22.024397] ? vprintk_emit+0x3ea/0x590 [ 22.025271] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 22.025679] do_invalid_op+0x1b/0x20 [ 22.025943] invalid_op+0x18/0x20 [ 22.026194] RIP: 0010:refcount_sub_and_test+0x167/0x1b0 [ 22.026568] RSP: 0018:ffff88006bf76300 EFLAGS: 00010282 [ 22.026932] RAX: 0000000000000026 RBX: 0000000000000001 RCX: 0000000000000000 [ 22.027427] RDX: 0000000000000026 RSI: 1ffff1000d7eec20 RDI: ffffed000d7eec54 [ 22.027917] RBP: ffff88006bf76390 R08: ffff88006bf759f0 R09: 0000000000000000 [ 22.028525] R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1000d7eec61 [ 22.029016] R13: 00000000ffffff01 R14: 0000000000000100 R15: ffff88006af27324 [ 22.029605] ? refcount_inc+0x50/0x50 [ 22.029942] ? __sctp_outq_teardown+0xc7d/0x15a0 [ 22.030366] ? sctp_association_free+0x2d0/0x930 [ 22.030783] ? sctp_do_sm+0x28e7/0x6dd0 [ 22.031137] ? sctp_primitive_SHUTDOWN+0xa0/0xd0 [ 22.031543] ? sctp_close+0x3c6/0x980 [ 22.031804] ? inet_release+0xed/0x1c0 [ 22.032082] sctp_wfree+0x183/0x620 [ 22.032339] ? __sctp_write_space+0x910/0x910 [ 22.032736] skb_release_head_state+0x124/0x200 [ 22.033148] skb_release_all+0x15/0x60 [ 22.033494] consume_skb+0x153/0x490 [ 22.033818] ? sctp_chunk_put+0x99/0x420 [ 22.034191] ? alloc_skb_with_frags+0x710/0x710 [ 22.034604] ? sctp_chunk_hold+0x20/0x20 [ 22.034963] ? refcount_sub_and_test+0x115/0x1b0 [ 22.035383] ? refcount_inc+0x50/0x50 [ 22.035719] ? mark_held_locks+0xb2/0x100 [ 22.036090] ? sctp_datamsg_put+0x456/0x560 [ 22.036479] sctp_chunk_put+0x29c/0x420 [ 22.036833] ? sctp_chunk_hold+0x20/0x20 [ 22.037195] ? sctp_transport_dst_confirm+0x50/0x50 [ 22.037648] sctp_chunk_free+0x53/0x60 [ 22.038001] __sctp_outq_teardown+0xc7d/0x15a0 [ 22.038315] ? inet6_release+0x50/0x70 [ 22.038621] ? sctp_inq_set_th_handler+0x1b0/0x1b0 [ 22.039048] ? unwind_next_frame.part.6+0x1ae/0xc70 [ 22.039495] ? unwind_next_frame.part.6+0x1ae/0xc70 [ 22.039937] ? unwind_dump+0x4c0/0x4c0 [ 22.040284] ? unwind_dump+0x4c0/0x4c0 [ 22.040635] ? copy_trace+0x1d0/0x1d0 [ 22.040976] ? check_noncircular+0x20/0x20 [ 22.041352] ? check_noncircular+0x20/0x20 [ 22.041728] ? unwind_get_return_address+0x61/0xa0 [ 22.042175] ? __save_stack_trace+0x61/0xd0 [ 22.042558] ? check_noncircular+0x20/0x20 [ 22.042951] ? print_usage_bug+0x480/0x480 [ 22.043334] ? find_held_lock+0x39/0x1d0 [ 22.043706] ? lock_downgrade+0x990/0x990 [ 22.044076] ? sk_dst_check+0x560/0x560 [ 22.044427] ? rcu_read_lock_sched_held+0x108/0x120 [ 22.044870] ? lock_release+0xd70/0xd70 [ 22.045225] sctp_outq_free+0x15/0x20 [ 22.045562] sctp_association_free+0x2d0/0x930 [ 22.046574] ? sctp_asconf_queue_teardown+0x700/0x700 [ 22.047031] ? sock_def_wakeup+0x222/0x350 [ 22.047433] ? sk_dst_check+0x560/0x560 [ 22.047789] ? sctp_association_put+0x74/0x2f0 [ 22.048191] ? sctp_association_hold+0x20/0x20 [ 22.048616] ? __unwind_start+0x169/0x330 [ 22.048986] ? sctp_sm_lookup_event+0x95/0x3c0 [ 22.049391] sctp_do_sm+0x28e7/0x6dd0 [ 22.049761] ? sctp_do_8_2_transport_strike.isra.16+0x8a0/0x8a0 [ 22.050286] ? print_usage_bug+0x480/0x480 [ 22.050650] ? print_usage_bug+0x480/0x480 [ 22.050987] ? find_held_lock+0x39/0x1d0 [ 22.051353] ? lock_downgrade+0x990/0x990 [ 22.051723] ? skb_dequeue+0x22/0x180 [ 22.052003] ? do_raw_spin_trylock+0x190/0x190 [ 22.052355] ? mark_held_locks+0xb2/0x100 [ 22.052645] ? trace_hardirqs_on+0xd/0x10 [ 22.052940] sctp_primitive_SHUTDOWN+0xa0/0xd0 [ 22.053342] sctp_close+0x3c6/0x980 [ 22.053666] ? sctp_apply_peer_addr_params+0xf30/0xf30 [ 22.054110] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 22.054502] ? trace_hardirqs_on+0xd/0x10 [ 22.054791] ? rcu_eqs_enter_common.constprop.73+0x270/0x270 [ 22.055193] ? ipv6_sock_ac_close+0x2e8/0x3e0 [ 22.055542] ? ipv6_sock_mc_close+0x148/0x1a0 [ 22.055852] ? ipv6_sock_ac_drop+0x580/0x580 [ 22.056106] ? ip_mc_drop_socket+0x1ce/0x230 [ 22.056360] ? __fsnotify_parent+0xb4/0x3a0 [ 22.056612] inet_release+0xed/0x1c0 [ 22.056838] inet6_release+0x50/0x70 [ 22.057055] sock_release+0x8d/0x1e0 [ 22.057272] ? sock_release+0x1e0/0x1e0 [ 22.057502] sock_close+0x16/0x20 [ 22.057703] __fput+0x333/0x7f0 [ 22.057901] ? fput+0x140/0x140 [ 22.058142] ? check_same_owner+0x320/0x320 [ 22.058506] ____fput+0x15/0x20 [ 22.058797] task_work_run+0x199/0x270 [ 22.059142] ? task_work_cancel+0x210/0x210 [ 22.059522] ? free_nsproxy+0x185/0x1f0 [ 22.059872] ? switch_task_namespaces+0xa2/0xc0 [ 22.060284] do_exit+0xa52/0x1b40 [ 22.060596] ? print_usage_bug+0x480/0x480 [ 22.060979] ? mm_update_next_owner+0x930/0x930 [ 22.061389] ? find_held_lock+0x39/0x1d0 [ 22.061750] ? check_noncircular+0x20/0x20 [ 22.062152] ? check_noncircular+0x20/0x20 [ 22.062528] ? lock_downgrade+0x990/0x990 [ 22.062904] ? reacquire_held_locks+0x205/0x3d0 [ 22.063335] ? check_noncircular+0x20/0x20 [ 22.063704] ? find_held_lock+0x39/0x1d0 [ 22.064069] ? lock_downgrade+0x990/0x990 [ 22.064429] ? lock_downgrade+0x990/0x990 [ 22.064795] ? find_held_lock+0x39/0x1d0 [ 22.065164] ? lock_downgrade+0x990/0x990 [ 22.065525] ? recalc_sigpending_tsk+0x117/0x150 [ 22.065942] ? recalc_sigpending+0x103/0x160 [ 22.066331] ? recalc_sigpending_tsk+0x150/0x150 [ 22.066743] ? get_signal+0x397/0x17e0 [ 22.067089] do_group_exit+0x149/0x400 [ 22.067678] ? __lock_is_held+0xbc/0x140 [ 22.068329] ? SyS_exit+0x30/0x30 [ 22.068633] ? _raw_spin_unlock_irq+0x27/0x70 [ 22.069027] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 22.069468] get_signal+0x7e8/0x17e0 [ 22.069825] ? ptrace_notify+0x130/0x130 [ 22.070197] ? __local_bh_enable_ip+0x9d/0x160 [ 22.070596] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 22.070957] ? release_sock+0x1d4/0x2a0 [ 22.071292] ? trace_hardirqs_on+0xd/0x10 [ 22.071589] ? __local_bh_enable_ip+0x9d/0x160 [ 22.071912] ? _raw_spin_unlock_bh+0x30/0x40 [ 22.072202] ? release_sock+0x1d4/0x2a0 [ 22.072479] ? trace_hardirqs_on+0xd/0x10 [ 22.072775] do_signal+0x94/0x1ee0 [ 22.073024] ? inet_sendmsg+0x11f/0x5e0 [ 22.073287] ? inet_sendmsg+0x126/0x5e0 [ 22.073553] ? __might_sleep+0x95/0x190 [ 22.073839] ? setup_sigcontext+0x7d0/0x7d0 [ 22.074199] ? selinux_socket_sendmsg+0x36/0x40 [ 22.074603] ? security_socket_sendmsg+0x89/0xb0 [ 22.074970] ? inet_recvmsg+0x5f0/0x5f0 [ 22.075245] ? sock_sendmsg+0x4f/0x110 [ 22.075514] ? fput+0xd2/0x140 [ 22.075745] ? SYSC_sendto+0x413/0x5a0 [ 22.076037] ? SYSC_connect+0x480/0x480 [ 22.076342] ? exit_to_usermode_loop+0x98/0x300 [ 22.076710] exit_to_usermode_loop+0x224/0x300 [ 22.077045] ? trace_event_raw_event_sys_exit+0x260/0x260 [ 22.077483] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 22.077918] syscall_return_slowpath+0x42f/0x500 [ 22.078308] ? finish_task_switch+0x1aa/0x740 [ 22.078697] ? prepare_exit_to_usermode+0x2c0/0x2c0 [ 22.079083] ? entry_SYSCALL_64_fastpath+0x91/0xbe [ 22.079505] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 22.079894] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 22.080262] entry_SYSCALL_64_fastpath+0xbc/0xbe [ 22.080583] RIP: 0033:0x43b279 [ 22.080800] RSP: 002b:00007f5cbc107db8 EFLAGS: 00000206 ORIG_RAX: 000000000000002c [ 22.081346] RAX: 0000000000000001 RBX: 0000000000000000 RCX: 000000000043b279 [ 22.081881] RDX: 0000000000000001 RSI: 0000000020018fff RDI: 0000000000000003 [ 22.082449] RBP: 0000000000000000 R08: 00000000206e4000 R09: 000000000000001c [ 22.083037] R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 [ 22.083579] R13: 0000000000000000 R14: 00007f5cbc1089c0 R15: 00007f5cbc108700 [ 22.084316] Dumping ftrace buffer: [ 22.084679] (ftrace buffer empty) [ 22.084929] Kernel Offset: disabled [ 22.085199] Rebooting in 86400 seconds..