[ OK ] Listening on Load/Save RF Kill Switch Status /dev/rfkill Watch. [ OK ] Started Getty on tty6. [ OK ] Started Getty on tty5. [ OK ] Started Getty on tty4. [ OK ] Started Getty on tty3. [ OK ] Started Getty on tty2. [ OK ] Started Getty on tty1. [ OK ] Started Serial Getty on ttyS0. [ OK ] Reached target Login Prompts. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... Starting Load/Save RF Kill Switch Status... [ OK ] Started Load/Save RF Kill Switch Status. [ OK ] Started Update UTMP about System Runlevel Changes. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.176' (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 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 executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 31.356329] refcount_t: underflow; use-after-free. [ 31.361676] ------------[ cut here ]------------ [ 31.366659] WARNING: CPU: 0 PID: 8303 at lib/refcount.c:281 refcount_dec_not_one.cold+0x18/0x25 [ 31.375738] Kernel panic - not syncing: panic_on_warn set ... [ 31.375738] [ 31.383588] CPU: 0 PID: 8303 Comm: systemd-udevd Not tainted 4.14.237-syzkaller #0 [ 31.391287] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 31.400763] Call Trace: [ 31.403339] dump_stack+0x1b2/0x281 [ 31.406972] panic+0x1f9/0x42d [ 31.410171] ? add_taint.cold+0x16/0x16 [ 31.414236] ? refcount_dec_not_one.cold+0x18/0x25 [ 31.419146] ? refcount_dec_not_one.cold+0x18/0x25 [ 31.424136] __warn.cold+0x20/0x44 [ 31.427705] ? ist_end_non_atomic+0x10/0x10 [ 31.432282] ? refcount_dec_not_one.cold+0x18/0x25 [ 31.437213] report_bug+0x208/0x250 [ 31.440911] do_error_trap+0x195/0x2d0 [ 31.444778] ? math_error+0x2d0/0x2d0 [ 31.448569] ? ___preempt_schedule+0x16/0x18 [ 31.452980] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 31.457816] invalid_op+0x1b/0x40 [ 31.461254] RIP: 0010:refcount_dec_not_one.cold+0x18/0x25 [ 31.466774] RSP: 0018:ffff888092417c38 EFLAGS: 00010286 [ 31.472206] RAX: 0000000000000026 RBX: 0000000000000000 RCX: 0000000000000000 [ 31.479485] RDX: 0000000000000000 RSI: ffffffff878bbbc0 RDI: ffffed1012482f7d [ 31.486849] RBP: ffff8880aaa2c698 R08: 0000000000000026 R09: 0000000000000000 [ 31.494394] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff [ 31.501655] R13: 0000000000000000 R14: ffffed10116acf1e R15: ffff8880aaa2c6a8 [ 31.508924] ? refcount_dec_not_one.cold+0x18/0x25 [ 31.513841] ? trace_hardirqs_on_caller+0x3a8/0x580 [ 31.518878] refcount_dec_and_mutex_lock+0x1a/0x60 [ 31.523855] nbd_config_put+0x506/0x810 [ 31.528015] nbd_release+0xdf/0x150 [ 31.531622] ? nbd_queue_rq+0xc50/0xc50 [ 31.535985] __blkdev_put+0x5aa/0x800 [ 31.539987] ? revalidate_disk+0x1f0/0x1f0 [ 31.544327] ? locks_remove_file+0x2cd/0x420 [ 31.548956] ? blkdev_put+0x75/0x4c0 [ 31.552974] ? blkdev_put+0x4c0/0x4c0 [ 31.556852] blkdev_close+0x86/0xb0 [ 31.560500] __fput+0x25f/0x7a0 [ 31.563944] task_work_run+0x11f/0x190 [ 31.568047] exit_to_usermode_loop+0x1ad/0x200 [ 31.572639] do_syscall_64+0x4a3/0x640 [ 31.576593] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 31.581789] RIP: 0033:0x7f07fff5d270 [ 31.585528] RSP: 002b:00007ffde151a618 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 [ 31.593669] RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f07fff5d270 [ 31.601023] RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007 [ 31.608453] RBP: 00007f0800e17710 R08: 000055783a0d6cd0 R09: 0000000000000018 [ 31.615707] R10: 000055783a0d51d8 R11: 0000000000000246 R12: 0000000000000000 [ 31.623668] R13: 000055783a0d06e0 R14: 0000000000000003 R15: 000000000000000e [ 31.632008] Kernel Offset: disabled [ 31.635664] Rebooting in 86400 seconds..