[ 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 '10.128.0.165' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 26.560318] [ 26.561950] ====================================================== [ 26.568240] WARNING: possible circular locking dependency detected [ 26.574636] 4.14.288-syzkaller #0 Not tainted [ 26.579211] ------------------------------------------------------ [ 26.585512] kworker/u4:4/2880 is trying to acquire lock: [ 26.590933] (sk_lock-AF_INET6){+.+.}, at: [] strp_work+0x3e/0x100 [ 26.598805] [ 26.598805] but task is already holding lock: [ 26.604748] ((&strp->work)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 [ 26.613131] [ 26.613131] which lock already depends on the new lock. [ 26.613131] [ 26.621417] [ 26.621417] the existing dependency chain (in reverse order) is: [ 26.629026] [ 26.629026] -> #1 ((&strp->work)){+.+.}: [ 26.634550] flush_work+0xad/0x770 [ 26.638587] __cancel_work_timer+0x321/0x460 [ 26.643492] strp_done+0x53/0xd0 [ 26.647359] kcm_ioctl+0x828/0xfb0 [ 26.651405] sock_ioctl+0x2cc/0x4c0 [ 26.655527] do_vfs_ioctl+0x75a/0xff0 [ 26.659826] SyS_ioctl+0x7f/0xb0 [ 26.663689] do_syscall_64+0x1d5/0x640 [ 26.668072] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 26.674187] [ 26.674187] -> #0 (sk_lock-AF_INET6){+.+.}: [ 26.679963] lock_acquire+0x170/0x3f0 [ 26.684259] lock_sock_nested+0xb7/0x100 [ 26.688810] strp_work+0x3e/0x100 [ 26.692768] process_one_work+0x793/0x14a0 [ 26.697495] worker_thread+0x5cc/0xff0 [ 26.701897] kthread+0x30d/0x420 [ 26.705779] ret_from_fork+0x24/0x30 [ 26.709984] [ 26.709984] other info that might help us debug this: [ 26.709984] [ 26.718099] Possible unsafe locking scenario: [ 26.718099] [ 26.724137] CPU0 CPU1 [ 26.728775] ---- ---- [ 26.733416] lock((&strp->work)); [ 26.736939] lock(sk_lock-AF_INET6); [ 26.743238] lock((&strp->work)); [ 26.749267] lock(sk_lock-AF_INET6); [ 26.753041] [ 26.753041] *** DEADLOCK *** [ 26.753041] [ 26.759072] 2 locks held by kworker/u4:4/2880: [ 26.763629] #0: ("%s""kstrp"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 [ 26.772283] #1: ((&strp->work)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 [ 26.781109] [ 26.781109] stack backtrace: [ 26.785583] CPU: 1 PID: 2880 Comm: kworker/u4:4 Not tainted 4.14.288-syzkaller #0 [ 26.793177] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022 [ 26.802517] Workqueue: kstrp strp_work [ 26.806378] Call Trace: [ 26.808969] dump_stack+0x1b2/0x281 [ 26.812569] print_circular_bug.constprop.0.cold+0x2d7/0x41e [ 26.818351] __lock_acquire+0x2e0e/0x3f20 [ 26.822473] ? __schedule+0x893/0x1de0 [ 26.826420] ? trace_hardirqs_on+0x10/0x10 [ 26.830626] ? lock_acquire+0x170/0x3f0 [ 26.834574] ? lock_sock_nested+0x98/0x100 [ 26.838792] lock_acquire+0x170/0x3f0 [ 26.842566] ? strp_work+0x3e/0x100 [ 26.846166] lock_sock_nested+0xb7/0x100 [ 26.850196] ? strp_work+0x3e/0x100 [ 26.853892] strp_work+0x3e/0x100 [ 26.857318] process_one_work+0x793/0x14a0 [