[ 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 '10.128.0.109' (ECDSA) to the list of known hosts. syzkaller login: [ 35.027019] IPVS: ftp: loaded support on port[0] = 21 executing program [ 35.102690] IPVS: ftp: loaded support on port[0] = 21 [ 35.181679] [ 35.183338] ====================================================== [ 35.189647] WARNING: possible circular locking dependency detected [ 35.195947] 4.19.156-syzkaller #0 Not tainted [ 35.200418] ------------------------------------------------------ [ 35.206711] kworker/1:2/4382 is trying to acquire lock: [ 35.212049] 000000009041c4f3 (&sb->s_type->i_mutex_key#13){+.+.}, at: __sock_release+0x86/0x2a0 [ 35.220879] [ 35.220879] but task is already holding lock: [ 35.226827] 00000000caacd63b ((delayed_fput_work).work){+.+.}, at: process_one_work+0x79c/0x1570 [ 35.235736] [ 35.235736] which lock already depends on the new lock. [ 35.235736] [ 35.244032] [ 35.244032] the existing dependency chain (in reverse order) is: [ 35.251627] [ 35.251627] -> #3 ((delayed_fput_work).work){+.+.}: [ 35.258383] worker_thread+0x64c/0x1130 [ 35.262857] kthread+0x33f/0x460 [ 35.266745] ret_from_fork+0x24/0x30 [ 35.270952] [ 35.270952] -> #2 ((wq_completion)"events"){+.+.}: [ 35.277345] tipc_exit_net+0x38/0x60 [ 35.281559] ops_exit_list+0xa5/0x150 [ 35.285860] cleanup_net+0x3b4/0x8b0 [ 35.290089] process_one_work+0x864/0x1570 [ 35.294824] worker_thread+0x64c/0x1130 [ 35.299311] kthread+0x33f/0x460 [ 35.303179] ret_from_fork+0x24/0x30 [ 35.307385] [ 35.307385] -> #1 (pernet_ops_rwsem){++++}: [ 35.313172] unregister_netdevice_notifier+0x7b/0x330 [ 35.318859] raw_release+0x58/0x820 [ 35.322987] __sock_release+0xcd/0x2a0 [ 35.327384] sock_close+0x15/0x20 [ 35.331357] __fput+0x2ce/0x890 [ 35.335139] task_work_run+0x148/0x1c0 [ 35.339526] exit_to_usermode_loop+0x251/0x2a0 [ 35.344609] do_syscall_64+0x538/0x620 [ 35.348996] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 35.354679] [ 35.354679] -> #0 (&sb->s_type->i_mutex_key#13){+.+.}: [ 35.361423] down_write+0x34/0x90 [ 35.365376] __sock_release+0x86/0x2a0 [ 35.369761] sock_close+0x15/0x20 [ 35.373716] __fput+0x2ce/0x890 [ 35.377496] delayed_fput+0x56/0x70 [ 35.381625] process_one_work+0x864/0x1570 [ 35.386358] worker_thread+0x64c/0x1130 [ 35.390831] kthread+0x33f/0x460 [ 35.394700] ret_from_fork+0x24/0x30 [ 35.398922] [ 35.398922] other info that might help us debug this: [ 35.398922] [ 35.407044] Chain exists of: [ 35.407044] &sb->s_type->i_mutex_key#13 --> (wq_completion)"events" --> (delayed_fput_work).work [ 35.407044] [ 35.420486] Possible unsafe locking scenario: [ 35.420486] [ 35.426520] CPU0 CPU1 [ 35.431176] ---- ---- [ 35.435822] lock((delayed_fput_work).work); [ 35.440293] lock((wq_completion)"events"); [ 35.447208] lock((delayed_fput_work).work); [ 35.454198] lock(&sb->s_type->i_mutex_key#13); [ 35.458931] [ 35.458931] *** DEADLOCK *** [ 35.458931] [ 35.464982] 2 locks held by kworker/1:2/4382: [ 35.469448] #0: 00000000138532ef ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 [ 35.478709] #1: 00000000caacd63b ((delayed_fput_work).work){+.+.}, at: process_one_work+0x79c/0x1570 [ 35.488051] [ 35.488051] stack backtrace: [ 35.492586] CPU: 1 PID: 4382 Comm: kworker/1:2 Not tainted 4.19.156-syzkaller #0 [ 35.500096] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 35.509437] Workqueue: events delayed_fput [ 35.513647] Call Trace: [ 35.516232] dump_stack+0x1fc/0x2fe [ 35.519843] print_circular_bug.constprop.0.cold+0x2d7/0x41e [ 35.525634] __lock_acquire+0x30c9/0x3ff0 [ 35.529764] ? mark_held_locks+0xf0/0xf0 [ 35.533827] ? mark_held_locks+0xf0/0xf0 [ 35.537890] ? __lock_acquire+0x6de/0x3ff0 [ 35.542131] ? update_curr+0x3b9/0x870 [ 35.546009] ? mark_held_locks+0xf0/0xf0 [ 35.550057] lock_acquire+0x170/0x3c0 [ 35.554109] ? __sock_release+0x86/0x2a0 [ 35.558679] down_write+0x34/0x90 [ 35.562117] ? __sock_release+0x86/0x2a0 [ 35.566159] __sock_release+0x86/0x2a0 [ 35.570027] ? __sock_release+0x2a0/0x2a0 [ 35.574152] sock_close+0x15/0x20 [ 35.577587] __fput+0x2ce/0x890 [ 35.581040] delayed_fput+