[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 66.745861][ T27] audit: type=1800 audit(1576628110.260:25): pid=9169 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 66.774933][ T27] audit: type=1800 audit(1576628110.260:26): pid=9169 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 66.824930][ T27] audit: type=1800 audit(1576628110.270:27): pid=9169 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 '10.128.10.38' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 79.502018][ T9321] ------------[ cut here ]------------ [ 79.507625][ T9321] refcount_t: underflow; use-after-free. [ 79.513502][ T9321] WARNING: CPU: 0 PID: 9321 at lib/refcount.c:28 refcount_warn_saturate+0x1dc/0x1f0 [ 79.522975][ T9321] Kernel panic - not syncing: panic_on_warn set ... [ 79.529552][ T9321] CPU: 0 PID: 9321 Comm: syz-executor338 Not tainted 5.5.0-rc2-next-20191217-syzkaller #0 [ 79.539416][ T9321] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 79.549456][ T9321] Call Trace: [ 79.552732][ T9321] dump_stack+0x197/0x210 [ 79.557046][ T9321] ? refcount_warn_saturate+0x140/0x1f0 [ 79.562587][ T9321] panic+0x2e3/0x75c [ 79.566476][ T9321] ? add_taint.cold+0x16/0x16 [ 79.571146][ T9321] ? __kasan_check_write+0x14/0x20 [ 79.576249][ T9321] ? __warn.cold+0x14/0x3e [ 79.580663][ T9321] ? __warn+0xd9/0x1cf [ 79.584815][ T9321] ? refcount_warn_saturate+0x1dc/0x1f0 [ 79.590360][ T9321] __warn.cold+0x2f/0x3e [ 79.594585][ T9321] ? refcount_warn_saturate+0x1dc/0x1f0 [ 79.600124][ T9321] report_bug+0x289/0x300 [ 79.604435][ T9321] do_error_trap+0x11b/0x200 [ 79.609031][ T9321] do_invalid_op+0x37/0x50 [ 79.613560][ T9321] ? refcount_warn_saturate+0x1dc/0x1f0 [ 79.619117][ T9321] invalid_op+0x23/0x30 [ 79.623299][ T9321] RIP: 0010:refcount_warn_saturate+0x1dc/0x1f0 [ 79.629520][ T9321] Code: e9 d8 fe ff ff 48 89 df e8 31 3d 23 fe e9 85 fe ff ff e8 d7 4f e5 fd 48 c7 c7 20 d9 6f 88 c6 05 38 8a ec 06 01 e8 23 de b5 fd <0f> 0b e9 ac fe ff ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 [ 79.649106][ T9321] RSP: 0018:ffffc90001dd7bf0 EFLAGS: 00010282 [ 79.655163][ T9321] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 79.663114][ T9321] RDX: 0000000000000000 RSI: ffffffff815e9766 RDI: fffff520003baf70 [ 79.671078][ T9321] RBP: ffffc90001dd7c00 R08: ffff8880a0bb2340 R09: ffffed1015d045c9 [ 79.679044][ T9321] R10: ffffed1015d045c8 R11: ffff8880ae822e43 R12: 0000000000000003 [ 79.687018][ T9321] R13: ffff8880a0109c58 R14: ffff8880a0109c00 R15: ffffffff8a023580 [ 79.694990][ T9321] ? vprintk_func+0x86/0x189 [ 79.699564][ T9321] put_watch+0xa2/0xb0 [ 79.703611][ T9321] watch_queue_release+0x34b/0xc40 [ 79.708723][ T9321] __fput+0x2ff/0x890 [ 79.712702][ T9321] ? __post_watch_notification+0x840/0x840 [ 79.718503][ T9321] ____fput+0x16/0x20 [ 79.722467][ T9321] task_work_run+0x145/0x1c0 [ 79.727059][ T9321] do_exit+0x909/0x2f20 [ 79.731201][ T9321] ? mm_update_next_owner+0x7c0/0x7c0 [ 79.736569][ T9321] ? __x64_sys_watch_devices+0x1e4/0x290 [ 79.742193][ T9321] ? rcu_read_lock_sched_held+0x9c/0xd0 [ 79.747729][ T9321] ? rcu_read_lock_any_held.part.0+0x50/0x50 [ 79.755008][ T9321] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 79.760461][ T9321] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 79.765976][ T9321] do_group_exit+0x135/0x360 [ 79.770593][ T9321] __x64_sys_exit_group+0x44/0x50 [ 79.775603][ T9321] do_syscall_64+0xfa/0x790 [ 79.780189][ T9321] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 79.786234][ T9321] RIP: 0033:0x43f168 [ 79.790117][ T9321] Code: Bad RIP value. [ 79.794163][ T9321] RSP: 002b:00007fffdf5554d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 79.802610][ T9321] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043f168 [ 79.810617][ T9321] RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000 [ 79.818597][ T9321] RBP: 00000000004be848 R08: 00000000000000e7 R09: ffffffffffffffd4 [ 79.826624][ T9321] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 [ 79.834590][ T9321] R13: 00000000006d0180 R14: 0000000000000000 R15: 0000000000000000 [ 79.844167][ T9321] Kernel Offset: disabled [ 79.848573][ T9321] Rebooting in 86400 seconds..