[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 40.636996][ T26] audit: type=1800 audit(1555822739.665:25): pid=7819 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 40.673157][ T26] audit: type=1800 audit(1555822739.665:26): pid=7819 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 40.695315][ T26] audit: type=1800 audit(1555822739.665:27): pid=7819 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 res=0 [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.1.4' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 54.634573][ T8016] ------------[ cut here ]------------ [ 54.640291][ T8016] percpu_ref_kill_and_confirm called more than once on io_ring_ctx_ref_free! [ 54.640674][ T8016] WARNING: CPU: 1 PID: 8016 at lib/percpu-refcount.c:335 percpu_ref_kill_and_confirm+0x341/0x3b0 [ 54.659911][ T8016] Kernel panic - not syncing: panic_on_warn set ... [ 54.666505][ T8016] CPU: 1 PID: 8016 Comm: syz-executor541 Not tainted 5.1.0-rc5+ #78 [ 54.674479][ T8016] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 54.684538][ T8016] Call Trace: [ 54.687932][ T8016] dump_stack+0x172/0x1f0 [ 54.692295][ T8016] ? percpu_ref_kill_and_confirm+0x340/0x3b0 [ 54.698284][ T8016] panic+0x2cb/0x65c [ 54.702167][ T8016] ? __warn_printk+0xf3/0xf3 [ 54.706747][ T8016] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 54.712713][ T8016] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 54.718939][ T8016] ? __warn.cold+0x5/0x45 [ 54.723277][ T8016] ? __warn+0xe8/0x1d0 [ 54.727351][ T8016] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 54.733359][ T8016] __warn.cold+0x20/0x45 [ 54.737625][ T8016] ? vprintk_emit+0x1ce/0x6d0 [ 54.742302][ T8016] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 54.748267][ T8016] report_bug+0x263/0x2b0 [ 54.752585][ T8016] do_error_trap+0x11b/0x200 [ 54.757161][ T8016] do_invalid_op+0x37/0x50 [ 54.761562][ T8016] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 54.767525][ T8016] invalid_op+0x14/0x20 [ 54.771667][ T8016] RIP: 0010:percpu_ref_kill_and_confirm+0x341/0x3b0 [ 54.778233][ T8016] Code: 42 e0 2a 06 01 48 89 fa 48 c1 ea 03 80 3c 02 00 75 76 49 8b 54 24 10 48 c7 c6 a0 71 a1 87 48 c7 c7 40 71 a1 87 e8 ad 92 13 fe <0f> 0b 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 80 3c 02 [ 54.797825][ T8016] RSP: 0018:ffff888091197cf0 EFLAGS: 00010082 [ 54.803896][ T8016] RAX: 0000000000000000 RBX: 0000607f5142d9b3 RCX: 0000000000000000 [ 54.811981][ T8016] RDX: 0000000000000000 RSI: ffffffff815afcf6 RDI: ffffed1012232f90 [ 54.823911][ T8016] RBP: ffff888091197d20 R08: ffff8880862cc100 R09: fffffbfff1133639 [ 54.831873][ T8016] R10: fffffbfff1133638 R11: ffffffff8899b1c3 R12: ffff8880a672eac0 [ 54.839848][ T8016] R13: ffff8880a672eac8 R14: 0000000000000286 R15: 0000000000000000 [ 54.847843][ T8016] ? vprintk_func+0x86/0x189 [ 54.852425][ T8016] __io_uring_register+0xa7/0x1fe0 [ 54.857520][ T8016] ? __mutex_lock+0x3cd/0x1310 [ 54.862266][ T8016] ? __x64_sys_io_uring_register+0x182/0x1f0 [ 54.868231][ T8016] ? mutex_trylock+0x1e0/0x1e0 [ 54.872987][ T8016] ? io_sq_wq_submit_work+0x10f0/0x10f0 [ 54.878518][ T8016] ? __x64_sys_futex+0x404/0x590 [ 54.883440][ T8016] __x64_sys_io_uring_register+0x193/0x1f0 [ 54.889236][ T8016] do_syscall_64+0x103/0x610 [ 54.893824][ T8016] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 54.899702][ T8016] RIP: 0033:0x4467c9 [ 54.903575][ T8016] Code: e8 5c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 0b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 54.923161][ T8016] RSP: 002b:00007fab6566edb8 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab [ 54.931561][ T8016] RAX: ffffffffffffffda RBX: 00000000006dbc38 RCX: 00000000004467c9 [ 54.939515][ T8016] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000003 [ 54.947472][ T8016] RBP: 00000000006dbc30 R08: 0000000000000000 R09: 0000000000000000 [ 54.955433][ T8016] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc3c [ 54.964522][ T8016] R13: 00007ffda48136df R14: 00007fab6566f9c0 R15: 20c49ba5e353f7cf [ 54.973309][ T8016] Kernel Offset: disabled [ 54.977716][ T8016] Rebooting in 86400 seconds..