[ OK ] Started Serial Getty on ttyS0. [ OK ] Started Getty on tty4. [ OK ] Started Getty on tty3. [ OK ] Started Getty on tty2. [ OK ] Started getty on tty2-tty6 if dbus and logind are not available. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.224' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 45.345951][ T6816] [ 45.348474][ T6816] ============================================ [ 45.354614][ T6816] WARNING: possible recursive locking detected [ 45.360773][ T6816] 5.8.0-syzkaller #0 Not tainted [ 45.365677][ T6816] -------------------------------------------- [ 45.371822][ T6816] syz-executor287/6816 is trying to acquire lock: [ 45.378200][ T6816] ffff888093cdb4d8 (&ctx->completion_lock){....}-{2:2}, at: __io_queue_deferred+0x36a/0x790 [ 45.388247][ T6816] [ 45.388247][ T6816] but task is already holding lock: [ 45.395578][ T6816] ffff888093cdb4d8 (&ctx->completion_lock){....}-{2:2}, at: io_cqring_overflow_flush+0xc6/0xab0 [ 45.405970][ T6816] [ 45.405970][ T6816] other info that might help us debug this: [ 45.414007][ T6816] Possible unsafe locking scenario: [ 45.414007][ T6816] [ 45.421443][ T6816] CPU0 [ 45.424703][ T6816] ---- [ 45.427952][ T6816] lock(&ctx->completion_lock); [ 45.432853][ T6816] lock(&ctx->completion_lock); [ 45.437766][ T6816] [ 45.437766][ T6816] *** DEADLOCK *** [ 45.437766][ T6816] [ 45.445922][ T6816] May be due to missing lock nesting notation [ 45.445922][ T6816] [ 45.454243][ T6816] 1 lock held by syz-executor287/6816: [ 45.459694][ T6816] #0: ffff888093cdb4d8 (&ctx->completion_lock){....}-{2:2}, at: io_cqring_overflow_flush+0xc6/0xab0 [ 45.470518][ T6816] [ 45.470518][ T6816] stack backtrace: [ 45.476379][ T6816] CPU: 1 PID: 6816 Comm: syz-executor287 Not tainted 5.8.0-syzkaller #0 [ 45.484663][ T6816] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 45.494686][ T6816] Call Trace: [ 45.497961][ T6816] dump_stack+0x1f0/0x31e [ 45.502263][ T6816] validate_chain+0x69a4/0x88a0 [ 45.507084][ T6816] ? select_task_rq_fair+0x51c/0x2c50 [ 45.512422][ T6816] ? mark_lock+0x102/0x1b00 [ 45.516894][ T6816] ? update_load_avg+0x53b/0x11d0 [ 45.521886][ T6816] __lock_acquire+0x1161/0x2ab0 [ 45.526705][ T6816] ? do_raw_spin_unlock+0x134/0x8d0 [ 45.531871][ T6816] lock_acquire+0x160/0x730 [ 45.536344][ T6816] ? __io_queue_deferred+0x36a/0x790 [ 45.541598][ T6816] _raw_spin_lock_irq+0x67/0x80 [ 45.546428][ T6816] ? __io_queue_deferred+0x36a/0x790 [ 45.551680][ T6816] __io_queue_deferred+0x36a/0x790 [ 45.556760][ T6816] io_cqring_overflow_flush+0x774/0xab0 [ 45.562274][ T6816] io_ring_ctx_wait_and_kill+0x2a1/0x570 [ 45.567884][ T6816] io_uring_release+0x59/0x70 [ 45.572564][ T6816] ? io_uring_flush+0xb50/0xb50 [ 45.577380][ T6816] __fput+0x34f/0x7b0 [ 45.581346][ T6816] task_work_run+0x137/0x1c0 [ 45.585904][ T6816] do_exit+0x5f3/0x1f20 [ 45.590048][ T6816] ? __se_sys_io_uring_enter+0x10cc/0x1300 [ 45.595822][ T6816] do_group_exit+0x161/0x2d0 [ 45.600384][ T6816] ? syscall_enter_from_user_mode+0x24/0x190 [ 45.606344][ T6816] __do_sys_exit_group+0x13/0x20 [ 45.611261][ T6816] __se_sys_exit_group+0x10/0x10 [ 45.616213][ T6816] __x64_sys_exit_group+0x37/0x40 [ 45.621205][ T6816] do_syscall_64+0x31/0x70 [ 45.625589][ T6816] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 45.631447][ T6816] RIP: 0033:0x43f598 [ 45.635304][ T6816] Code: Bad RIP value. [ 45.639354][ T6816] RSP: 002b:00007fffdac2bf58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 45.647731][ T6816] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043f598 [ 45.655672][ T6816] RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000 [ 45.663610][ T6816] RBP: 00000000004beda8 R08: 00000000000000e7 R09: ffffffffffffffd0 [ 45.671548][ T6816] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 [ 45.679484][ T6816] R13: 00000000006d11a0 R14: 0000000000000000 R15: 0000000000000000