[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 37.505132][ T26] audit: type=1800 audit(1555804619.101:25): pid=7633 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 37.541409][ T26] audit: type=1800 audit(1555804619.101:26): pid=7633 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 37.569578][ T26] audit: type=1800 audit(1555804619.101:27): pid=7633 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 '10.128.0.52' (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 syzkaller login: [ 51.751627][ T7815] ------------[ cut here ]------------ [ 51.757352][ T7815] percpu_ref_kill_and_confirm called more than once on io_ring_ctx_ref_free! [ 51.757556][ T7815] WARNING: CPU: 1 PID: 7815 at lib/percpu-refcount.c:335 percpu_ref_kill_and_confirm+0x341/0x3b0 [ 51.776862][ T7815] Kernel panic - not syncing: panic_on_warn set ... [ 51.783458][ T7815] CPU: 1 PID: 7815 Comm: syz-executor269 Not tainted 5.1.0-rc5+ #77 [ 51.791432][ T7815] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 51.801471][ T7815] Call Trace: [ 51.804839][ T7815] dump_stack+0x172/0x1f0 [ 51.809158][ T7815] ? percpu_ref_kill_and_confirm+0x340/0x3b0 [ 51.815282][ T7815] panic+0x2cb/0x65c [ 51.819188][ T7815] ? __warn_printk+0xf3/0xf3 [ 51.823771][ T7815] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 51.829769][ T7815] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 51.836028][ T7815] ? __warn.cold+0x5/0x45 [ 51.840352][ T7815] ? __warn+0xe8/0x1d0 [ 51.844442][ T7815] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 51.850440][ T7815] __warn.cold+0x20/0x45 [ 51.854761][ T7815] ? vprintk_emit+0x1ce/0x6d0 [ 51.859464][ T7815] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 51.865431][ T7815] report_bug+0x263/0x2b0 [ 51.869759][ T7815] do_error_trap+0x11b/0x200 [ 51.874365][ T7815] do_invalid_op+0x37/0x50 [ 51.878770][ T7815] ? percpu_ref_kill_and_confirm+0x341/0x3b0 [ 51.884754][ T7815] invalid_op+0x14/0x20 [ 51.888924][ T7815] RIP: 0010:percpu_ref_kill_and_confirm+0x341/0x3b0 [ 51.895521][ T7815] 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 [ 51.915548][ T7815] RSP: 0018:ffff8880a96cfce0 EFLAGS: 00010086 [ 51.921606][ T7815] RAX: 0000000000000000 RBX: 0000607f5142e35b RCX: 0000000000000000 [ 51.929628][ T7815] RDX: 0000000000000000 RSI: ffffffff815afcf6 RDI: ffffed10152d9f8e [ 51.937585][ T7815] RBP: ffff8880a96cfd10 R08: ffff8880a85c40c0 R09: fffffbfff1133639 [ 51.945543][ T7815] R10: fffffbfff1133638 R11: ffffffff8899b1c3 R12: ffff88809ee571c0 [ 51.953523][ T7815] R13: ffff88809ee571c8 R14: 0000000000000286 R15: 0000000000000000 [ 51.961504][ T7815] ? vprintk_func+0x86/0x189 [ 51.966089][ T7815] __io_uring_register+0xa7/0x1fe0 [ 51.971218][ T7815] ? __mutex_lock+0x3cd/0x1310 [ 51.975995][ T7815] ? __ia32_sys_io_uring_register+0x182/0x1f0 [ 51.982061][ T7815] ? mutex_trylock+0x1e0/0x1e0 [ 51.986825][ T7815] ? io_sq_wq_submit_work+0x10f0/0x10f0 [ 51.992373][ T7815] ? calculate_sigpending+0x87/0xa0 [ 51.997606][ T7815] __ia32_sys_io_uring_register+0x193/0x1f0 [ 52.003529][ T7815] do_fast_syscall_32+0x281/0xc98 [ 52.008552][ T7815] entry_SYSENTER_compat+0x70/0x7f [ 52.013671][ T7815] RIP: 0023:0xf7f16869 [ 52.017739][ T7815] Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 [ 52.037421][ T7815] RSP: 002b:00000000f7ef11ec EFLAGS: 00000296 ORIG_RAX: 00000000000001ab [ 52.045824][ T7815] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000 [ 52.053784][ T7815] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 52.061763][ T7815] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 52.069767][ T7815] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 52.077729][ T7815] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 52.086662][ T7815] Kernel Offset: disabled [ 52.091063][ T7815] Rebooting in 86400 seconds..