[  OK  ] Started Getty on tty3.
[  OK  ] Started Getty on tty2.
[  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...
[  OK  ] Started Update UTMP about System Runlevel Changes.
         Starting Load/Save RF Kill Switch Status...
[  OK  ] Started Load/Save RF Kill Switch Status.

Debian GNU/Linux 9 syzkaller ttyS0

Warning: Permanently added '10.128.0.75' (ECDSA) to the list of known hosts.
executing program
syzkaller login: [   27.732190] 
[   27.733853] ======================================================
[   27.740180] WARNING: possible circular locking dependency detected
[   27.746481] 4.14.288-syzkaller #0 Not tainted
[   27.750962] ------------------------------------------------------
[   27.757256] kworker/u4:0/5 is trying to acquire lock:
[   27.762430]  (sk_lock-AF_INET6){+.+.}, at: [<ffffffff8681dfbe>] strp_work+0x3e/0x100
[   27.770337] 
[   27.770337] but task is already holding lock:
[   27.776284]  ((&strp->work)){+.+.}, at: [<ffffffff81364f26>] process_one_work+0x6e6/0x14a0
[   27.784665] 
[   27.784665] which lock already depends on the new lock.
[   27.784665] 
[   27.792951] 
[   27.792951] the existing dependency chain (in reverse order) is:
[   27.800566] 
[   27.800566] -> #1 ((&strp->work)){+.+.}:
[   27.806096]        flush_work+0xad/0x770
[   27.810133]        __cancel_work_timer+0x321/0x460
[   27.815048]        strp_done+0x53/0xd0
[   27.818927]        kcm_ioctl+0x828/0xfb0
[   27.822968]        sock_ioctl+0x2cc/0x4c0
[   27.827106]        do_vfs_ioctl+0x75a/0xff0
[   27.831409]        SyS_ioctl+0x7f/0xb0
[   27.835404]        do_syscall_64+0x1d5/0x640
[   27.839884]        entry_SYSCALL_64_after_hwframe+0x46/0xbb
[   27.845572] 
[   27.845572] -> #0 (sk_lock-AF_INET6){+.+.}:
[   27.851355]        lock_acquire+0x170/0x3f0
[   27.855670]        lock_sock_nested+0xb7/0x100
[   27.860232]        strp_work+0x3e/0x100
[   27.864183]        process_one_work+0x793/0x14a0
[   27.868912]        worker_thread+0x5cc/0xff0
[   27.873291]        kthread+0x30d/0x420
[   27.877155]        ret_from_fork+0x24/0x30
[   27.881366] 
[   27.881366] other info that might help us debug this:
[   27.881366] 
[   27.889498]  Possible unsafe locking scenario:
[   27.889498] 
[   27.895540]        CPU0                    CPU1
[   27.900177]        ----                    ----
[   27.904827]   lock((&strp->work));
[   27.908339]                                lock(sk_lock-AF_INET6);
[   27.914627]                                lock((&strp->work));
[   27.920660]   lock(sk_lock-AF_INET6);
[   27.924435] 
[   27.924435]  *** DEADLOCK ***
[   27.924435] 
[   27.930467] 2 locks held by kworker/u4:0/5:
[   27.934759]  #0:  ("%s""kstrp"){+.+.}, at: [<ffffffff81364ef0>] process_one_work+0x6b0/0x14a0
[   27.943582]  #1:  ((&strp->work)){+.+.}, at: [<ffffffff81364f26>] process_one_work+0x6e6/0x14a0
[   27.952398] 
[   27.952398] stack backtrace:
[   27.956881] CPU: 0 PID: 5 Comm: kworker/u4:0 Not tainted 4.14.288-syzkaller #0
[   27.964210] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
[   27.973547] Workqueue: kstrp strp_work
[   27.977843] Call Trace:
[   27.980407]  dump_stack+0x1b2/0x281
[   27.984134]  print_circular_bug.constprop.0.cold+0x2d7/0x41e
[   27.989926]  __lock_acquire+0x2e0e/0x3f20
[   27.994054]  ? __schedule+0x893/0x1de0
[   27.997923]  ? trace_hardirqs_on+0x10/0x10
[   28.002146]  ? lock_acquire+0x170/0x3f0
[   28.006104]  ? lock_sock_nested+0x98/0x100
[   28.010324]  lock_acquire+0x170/0x3f0
[   28.014101]  ? strp_work+0x3e/0x100
[   28.017709]  lock_sock_nested+0xb7/0x100
[   28.021744]  ? strp_work+0x3e/0x100
[   28.025345]  strp_work+0x3e/0x100
[   28.028773]  process_one_work+0x793/0x14a0
[   28.