[ OK ] Started OpenBSD Secure Shell server. [ OK ] Started getty on tty2-tty6 if dbus and logind are not available. [ 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 Serial Getty on ttyS0. [ OK ] Started Getty on tty1. [ OK ] Reached target Login Prompts. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... [ OK ] Started Update UTMP about System Runlevel Changes. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.1.27' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 61.213944][ T6854] [ 61.216468][ T6854] ============================================ [ 61.222706][ T6854] WARNING: possible recursive locking detected [ 61.228984][ T6854] 5.9.0-rc2-syzkaller #0 Not tainted [ 61.234519][ T6854] -------------------------------------------- [ 61.240775][ T6854] syz-executor567/6854 is trying to acquire lock: [ 61.247218][ T6854] ffff88809abf8298 (&sighand->siglock){....}-{2:2}, at: __lock_task_sighand+0x106/0x2d0 [ 61.256924][ T6854] [ 61.256924][ T6854] but task is already holding lock: [ 61.264275][ T6854] ffff88809abf8298 (&sighand->siglock){....}-{2:2}, at: force_sig_info_to_task+0x6c/0x3a0 [ 61.274200][ T6854] [ 61.274200][ T6854] other info that might help us debug this: [ 61.282332][ T6854] Possible unsafe locking scenario: [ 61.282332][ T6854] [ 61.289766][ T6854] CPU0 [ 61.293063][ T6854] ---- [ 61.296376][ T6854] lock(&sighand->siglock); [ 61.301037][ T6854] lock(&sighand->siglock); [ 61.305675][ T6854] [ 61.305675][ T6854] *** DEADLOCK *** [ 61.305675][ T6854] [ 61.313811][ T6854] May be due to missing lock nesting notation [ 61.313811][ T6854] [ 61.322151][ T6854] 3 locks held by syz-executor567/6854: [ 61.327675][ T6854] #0: ffff88809abf8298 (&sighand->siglock){....}-{2:2}, at: force_sig_info_to_task+0x6c/0x3a0 [ 61.337998][ T6854] #1: ffff88809abf82e0 (&sighand->signalfd_wqh){....}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 [ 61.348779][ T6854] #2: ffffffff89bd6900 (rcu_read_lock){....}-{1:2}, at: __lock_task_sighand+0x0/0x2d0 [ 61.358398][ T6854] [ 61.358398][ T6854] stack backtrace: [ 61.364361][ T6854] CPU: 1 PID: 6854 Comm: syz-executor567 Not tainted 5.9.0-rc2-syzkaller #0 [ 61.373140][ T6854] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 61.383258][ T6854] Call Trace: [ 61.386581][ T6854] dump_stack+0x18f/0x20d [ 61.391051][ T6854] __lock_acquire.cold+0x115/0x396 [ 61.396205][ T6854] ? lockdep_hardirqs_on_prepare+0x530/0x530 [ 61.402176][ T6854] ? lockdep_hardirqs_on_prepare+0x530/0x530 [ 61.408145][ T6854] lock_acquire+0x1f1/0xad0 [ 61.412672][ T6854] ? __lock_task_sighand+0x106/0x2d0 [ 61.417960][ T6854] ? lock_release+0x8e0/0x8e0 [ 61.422659][ T6854] ? lock_release+0x8e0/0x8e0 [ 61.427406][ T6854] ? lockdep_hardirqs_on_prepare+0x530/0x530 [ 61.433399][ T6854] ? __lock_acquire+0x2e85/0x5640 [ 61.438497][ T6854] _raw_spin_lock_irqsave+0x8c/0xc0 [ 61.443678][ T6854] ? __lock_task_sighand+0x106/0x2d0 [ 61.448946][ T6854] __lock_task_sighand+0x106/0x2d0 [ 61.454076][ T6854] ? __io_async_wake+0x34f/0x980 [ 61.459029][ T6854] task_work_add+0x1d7/0x290 [ 61.463812][ T6854] ? cpumask_weight.constprop.0+0x3f/0x3f [ 61.469518][ T6854] ? lock_is_held_type+0xbb/0xf0 [ 61.474524][ T6854] __io_async_wake+0x415/0x980 [ 61.479288][ T6854] ? do_raw_spin_lock+0x120/0x2b0 [ 61.484296][ T6854] ? io_async_task_func+0x990/0x990 [ 61.489516][ T6854] ? lock_is_held_type+0xbb/0xf0 [ 61.494613][ T6854] ? rwlock_bug.part.0+0x90/0x90 [ 61.499539][ T6854] __wake_up_common+0x147/0x650 [ 61.504415][ T6854] __wake_up_common_lock+0xd0/0x130 [ 61.509606][ T6854] ? __wake_up_common+0x650/0x650 [ 61.514689][ T6854] ? __sigqueue_alloc+0x236/0x550 [ 61.519820][ T6854] ? rcu_read_lock_sched_held+0x3a/0xb0 [ 61.525348][ T6854] ? __sigqueue_alloc+0x2e4/0x550 [ 61.530489][ T6854] __send_signal+0x75b/0xf90 [ 61.535116][ T6854] force_sig_info_to_task+0x2a0/0x3a0 [ 61.540473][ T6854] force_sig_fault+0xb0/0xf0 [ 61.545047][ T6854] ? force_sig_fault_to_task+0xe0/0xe0 [ 61.550487][ T6854] ? arch_local_irq_disable+0x50/0x50 [ 61.555928][ T6854] ? _down_write_nest_lock+0x150/0x150 [ 61.561373][ T6854] __bad_area_nosemaphore+0x32a/0x480 [ 61.566775][ T6854] do_user_addr_fault+0x852/0xbf0 [ 61.571872][ T6854] ? rcu_read_lock_sched_held+0x3a/0xb0 [ 61.577403][ T6854] exc_page_fault+0xa8/0x160 [ 61.581974][ T6854] ? asm_exc_page_fault+0x8/0x30 [ 61.586906][ T6854] asm_exc_page_fault+0x1e/0x30 [ 61.591786][ T6854] RIP: 0033:0x400d4d [ 61.595674][ T6854] Code: 48 8b 54 24 e0 8b 86 0c 01 00 00 44 8b 86 08 01 00 00 c1 e0 04 8d b8 7f 01 00 00 83 e7 c0 45 85 c0 74 07 89 d0 31 d2 41 f7 f0 <4c> 8b 01 89 d0 c1 e0 06 4c 01 c8 4c 89 00 4c 8b 41 08 4c 89 40 08 [ 61.615583][ T6854] RSP: 002b:00007ffe74828db8 EFLAGS: 00010246 [ 61.621827][ T6854] RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000000000 [ 61.630064][ T6854] RDX: 0000000000000005 RSI: 0000000020ee7000 RDI: 0000000000002140 [ 61.638612][ T6854] RBP: 00000000006ca018 R08: 0000000000000100 R09: 0000000000000000 [ 61.646573][ T6854] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401d20 [ 61.654644][ T6854] R13: 0000000000401db0 R14: 0000000000000000 R15: 0000000000000000