[ OK ] Started Getty on tty2. [ OK ] Started Getty on tty1. [ 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... 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 '10.128.0.235' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 28.407795] [ 28.409480] ====================================================== [ 28.415770] WARNING: possible circular locking dependency detected [ 28.422058] 4.14.207-syzkaller #0 Not tainted [ 28.426568] ------------------------------------------------------ [ 28.432857] kworker/u4:3/340 is trying to acquire lock: [ 28.438227] (sk_lock-AF_INET){+.+.}, at: [] strp_work+0x3e/0x100 [ 28.446003] [ 28.446003] but task is already holding lock: [ 28.451943] ((&strp->work)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 [ 28.460324] [ 28.460324] which lock already depends on the new lock. [ 28.460324] [ 28.468609] [ 28.468609] the existing dependency chain (in reverse order) is: [ 28.476198] [ 28.476198] -> #1 ((&strp->work)){+.+.}: [ 28.481709] flush_work+0xad/0x770 [ 28.485740] __cancel_work_timer+0x321/0x460 [ 28.490641] strp_done+0x53/0xd0 [ 28.494497] kcm_ioctl+0x828/0xfb0 [ 28.498529] sock_ioctl+0x2cc/0x4c0 [ 28.502650] do_vfs_ioctl+0x75a/0xff0 [ 28.506940] SyS_ioctl+0x7f/0xb0 [ 28.510799] do_syscall_64+0x1d5/0x640 [ 28.515178] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 28.520856] [ 28.520856] -> #0 (sk_lock-AF_INET){+.+.}: [ 28.526559] lock_acquire+0x170/0x3f0 [ 28.530852] lock_sock_nested+0xb7/0x100 [ 28.535405] strp_work+0x3e/0x100 [ 28.539362] process_one_work+0x793/0x14a0 [ 28.544088] worker_thread+0x5cc/0xff0 [ 28.548503] kthread+0x30d/0x420 [ 28.552364] ret_from_fork+0x24/0x30 [ 28.556606] [ 28.556606] other info that might help us debug this: [ 28.556606] [ 28.564715] Possible unsafe locking scenario: [ 28.564715] [ 28.570741] CPU0 CPU1 [ 28.575376] ---- ---- [ 28.580011] lock((&strp->work)); [ 28.583523] lock(sk_lock-AF_INET); [ 28.589741] lock((&strp->work)); [ 28.595767] lock(sk_lock-AF_INET); [ 28.599451] [ 28.599451] *** DEADLOCK *** [ 28.599451] [ 28.605480] 2 locks held by kworker/u4:3/340: [ 28.609943] #0: ("%s""kstrp"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 [ 28.618599] #1: ((&strp->work)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 [ 28.627414] [ 28.627414] stack backtrace: [ 28.632837] CPU: 1 PID: 340 Comm: kworker/u4:3 Not tainted 4.14.207-syzkaller #0 [ 28.640338] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.649673] Workqueue: kstrp strp_work [ 28.653543] Call Trace: [ 28.656120] dump_stack+0x1b2/0x283 [ 28.659722] print_circular_bug.constprop.0.cold+0x2d7/0x41e [ 28.665491] __lock_acquire+0x2e0e/0x3f20 [ 28.669610] ? __schedule+0x893/0x1de0 [ 28.673468] ? trace_hardirqs_on+0x10/0x10 [ 28.677673] ? lock_acquire+0x170/0x3f0 [ 28.681640] ? lock_sock_nested+0x98/0x100 [ 28.685847] lock_acquire+0x170/0x3f0 [ 28.689619] ? strp_work+0x3e/0x100 [ 28.693217] lock_sock_nested+0xb7/0x100 [ 28.697262] ? strp_work+0x3e/0x100 [ 28.700857] strp_work+0x3e/0x100 [ 28.704283] process_one_work+0x793/0x14a0 [ 28.7