[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [ 52.784548][ T27] audit: type=1800 audit(1582996741.982:25): pid=8622 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="cron" dev="sda1" ino=2414 res=0 [ 52.803588][ T27] audit: type=1800 audit(1582996741.992:26): pid=8622 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="mcstrans" dev="sda1" ino=2457 res=0 [ 52.844130][ T27] audit: type=1800 audit(1582996741.992:27): pid=8622 uid=0 auid=4294967295 ses=4294967295 subj=_ 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 '10.128.0.25' (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 executing program executing program executing program executing program syzkaller login: [ 65.481856][ T2801] ------------[ cut here ]------------ [ 65.487873][ T2801] refcount_t: underflow; use-after-free. [ 65.503124][ T2801] WARNING: CPU: 1 PID: 2801 at lib/refcount.c:28 refcount_warn_saturate+0x165/0x1b0 [ 65.512526][ T2801] Kernel panic - not syncing: panic_on_warn set ... [ 65.519113][ T2801] CPU: 1 PID: 2801 Comm: kworker/1:12 Not tainted 5.6.0-rc3-syzkaller #0 [ 65.527523][ T2801] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 65.537590][ T2801] Workqueue: events do_enable_set [ 65.542612][ T2801] Call Trace: [ 65.545909][ T2801] dump_stack+0x1fb/0x318 [ 65.550276][ T2801] panic+0x264/0x7a9 [ 65.554225][ T2801] ? __warn+0x105/0x210 [ 65.558388][ T2801] ? refcount_warn_saturate+0x165/0x1b0 [ 65.563945][ T2801] __warn+0x209/0x210 [ 65.567949][ T2801] ? refcount_warn_saturate+0x165/0x1b0 [ 65.573513][ T2801] report_bug+0x1b6/0x2f0 [ 65.577855][ T2801] ? refcount_warn_saturate+0x165/0x1b0 [ 65.583412][ T2801] do_error_trap+0xcf/0x1c0 [ 65.587929][ T2801] do_invalid_op+0x36/0x40 [ 65.592369][ T2801] ? refcount_warn_saturate+0x165/0x1b0 [ 65.597930][ T2801] invalid_op+0x23/0x30 [ 65.602106][ T2801] RIP: 0010:refcount_warn_saturate+0x165/0x1b0 [ 65.608257][ T2801] Code: c7 24 e3 f0 88 31 c0 e8 b9 2d a8 fd 0f 0b eb 83 e8 f0 67 d6 fd c6 05 aa 31 c5 05 01 48 c7 c7 50 e3 f0 88 31 c0 e8 9b 2d a8 fd <0f> 0b e9 62 ff ff ff e8 cf 67 d6 fd c6 05 8a 31 c5 05 01 48 c7 c7 [ 65.627965][ T2801] RSP: 0018:ffffc9000871fbf0 EFLAGS: 00010246 [ 65.634036][ T2801] RAX: 25994bc5ee083f00 RBX: 0000000000000003 RCX: ffff88809f34a440 [ 65.642025][ T2801] RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 [ 65.650003][ T2801] RBP: ffffc9000871fc00 R08: ffffffff81600324 R09: ffffed1015d66618 [ 65.657978][ T2801] R10: ffffed1015d66618 R11: 0000000000000000 R12: ffff8880a6985018 [ 65.665969][ T2801] R13: dffffc0000000000 R14: 0000000000000003 R15: ffff88809f2e9280 [ 65.673979][ T2801] ? vprintk_emit+0x2d4/0x3a0 [ 65.678680][ T2801] l2cap_chan_put+0x18d/0x190 [ 65.683373][ T2801] do_enable_set+0x66c/0x900 [ 65.688296][ T2801] process_one_work+0x7f5/0x10f0 [ 65.693276][ T2801] worker_thread+0xbbc/0x1630 [ 65.697997][ T2801] kthread+0x332/0x350 [ 65.702133][ T2801] ? rcu_lock_release+0x30/0x30 [ 65.707003][ T2801] ? kthread_blkcg+0xe0/0xe0 [ 65.711613][ T2801] ret_from_fork+0x24/0x30 [ 65.717211][ T2801] Kernel Offset: disabled [ 65.721584][ T2801] Rebooting in 86400 seconds..