[ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... Starting Load/Save RF Kill Switch Status... [ OK ] Started Update UTMP about System Runlevel Changes. [ OK ] Started Load/Save RF Kill Switch Status. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.196' (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 syzkaller login: [ 28.869268] refcount_t: underflow; use-after-free. [ 28.874651] ------------[ cut here ]------------ [ 28.879483] WARNING: CPU: 0 PID: 8192 at lib/refcount.c:281 refcount_dec_not_one.cold+0x18/0x25 [ 28.888293] Kernel panic - not syncing: panic_on_warn set ... [ 28.888293] [ 28.895631] CPU: 0 PID: 8192 Comm: systemd-udevd Not tainted 4.14.280-syzkaller #0 [ 28.903309] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.912636] Call Trace: [ 28.915202] dump_stack+0x1b2/0x281 [ 28.918810] panic+0x1f9/0x42d [ 28.921975] ? add_taint.cold+0x16/0x16 [ 28.925925] ? refcount_dec_not_one.cold+0x18/0x25 [ 28.930835] ? refcount_dec_not_one.cold+0x18/0x25 [ 28.935736] __warn.cold+0x20/0x44 [ 28.939249] ? ist_end_non_atomic+0x10/0x10 [ 28.943549] ? refcount_dec_not_one.cold+0x18/0x25 [ 28.948453] report_bug+0x208/0x250 [ 28.952060] do_error_trap+0x195/0x2d0 [ 28.955921] ? math_error+0x2d0/0x2d0 [ 28.959700] ? ___preempt_schedule+0x16/0x18 [ 28.964085] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 28.968903] invalid_op+0x1b/0x40 [ 28.972333] RIP: 0010:refcount_dec_not_one.cold+0x18/0x25 [ 28.977839] RSP: 0018:ffff8880b3057c38 EFLAGS: 00010286 [ 28.983177] RAX: 0000000000000026 RBX: 0000000000000000 RCX: 0000000000000000 [ 28.990421] RDX: 0000000000000000 RSI: ffffffff878bc600 RDI: ffffed101660af7d [ 28.997669] RBP: ffff8880aacd9d58 R08: 0000000000000026 R09: 0000000000000000 [ 29.004915] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff [ 29.012164] R13: 0000000000000000 R14: ffffed101199ca9e R15: ffff8880aacd9d68 [ 29.019422] ? refcount_dec_not_one.cold+0x18/0x25 [ 29.024327] ? trace_hardirqs_on_caller+0x3a8/0x580 [ 29.029318] refcount_dec_and_mutex_lock+0x1a/0x60 [ 29.034220] nbd_config_put+0x506/0x810 [ 29.038167] nbd_release+0xdf/0x150 [ 29.041767] ? nbd_queue_rq+0xc50/0xc50 [ 29.045717] __blkdev_put+0x5aa/0x800 [ 29.049499] ? revalidate_disk+0x1f0/0x1f0 [ 29.053708] ? locks_remove_file+0x2cd/0x420 [ 29.058094] ? blkdev_put+0x75/0x4c0 [ 29.061785] ? blkdev_put+0x4c0/0x4c0 [ 29.065562] blkdev_close+0x86/0xb0 [ 29.069193] __fput+0x25f/0x7a0 [ 29.072465] task_work_run+0x11f/0x190 [ 29.076331] exit_to_usermode_loop+0x1ad/0x200 [ 29.080890] do_syscall_64+0x4a3/0x640 [ 29.084759] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 29.089936] RIP: 0033:0x7fea50006270 [ 29.093622] RSP: 002b:00007ffdaf5bb9b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 [ 29.101303] RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007fea50006270 [ 29.108550] RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007 [ 29.115798] RBP: 00007fea50ec0710 R08: 000055ff7d1cfd20 R09: 0000000000000018 [ 29.123041] R10: 000055ff7d1d1d78 R11: 0000000000000246 R12: 0000000000000000 [ 29.130286] R13: 000055ff7d1cb6e0 R14: 0000000000000003 R15: 000000000000000e [ 29.137903] Kernel Offset: disabled [ 29.141553] Rebooting in 86400 seconds..