INFO: task kworker/u4:8:9635 blocked for more than 140 seconds. Not tainted 4.19.211-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:8 D25496 9635 2 0x80000000 Workqueue: netns cleanup_net Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x887/0x2040 kernel/sched/core.c:3517 schedule+0x8d/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x92d/0xfe0 kernel/time/timer.c:1794 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common+0x29c/0x470 kernel/sched/completion.c:115 flush_workqueue+0x40b/0x13e0 kernel/workqueue.c:2713 flush_scheduled_work include/linux/workqueue.h:599 [inline] tipc_exit_net+0x38/0x60 net/tipc/core.c:100 ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153 cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:554 process_one_work+0x864/0x1570 kernel/workqueue.c:2153 worker_thread+0x64c/0x1130 kernel/workqueue.c:2296 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Showing all locks held in the system: 1 lock held by khungtaskd/1570: #0: 00000000f9fd7759 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4441 2 locks held by kworker/0:2/3688: #0: 0000000092faa606 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124 #1: 000000001c9d16d6 ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128 3 locks held by kworker/1:3/4701: 1 lock held by in:imklog/7819: 3 locks held by kworker/0:3/9352: 2 locks held by kworker/0:4/9357: #0: 0000000092faa606 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124 #1: 000000001db00b38 ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128 3 locks held by kworker/u4:8/9635: #0: 0000000095b8699a ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124 #1: 000000007907d734 (net_cleanup_work){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128 #2: 00000000ee158f7e (pernet_ops_rwsem){++++}, at: cleanup_net+0xa8/0x8b0 net/core/net_namespace.c:521 3 locks held by kworker/u4:10/18971: 4 locks held by syz-executor.2/28603: 1 lock held by syz-executor.3/28599: #0: 0000000090dcd23a (&type->s_umount_key#25/1){+.+.}, at: alloc_super fs/super.c:226 [inline] #0: 0000000090dcd23a (&type->s_umount_key#25/1){+.+.}, at: sget_userns+0x20b/0xcd0 fs/super.c:519 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1570 Comm: khungtaskd Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fc/0x2ef lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1a6/0x1f0 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline] watchdog+0x991/0xe60 kernel/hung_task.c:287 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 28603 Comm: syz-executor.2 Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023 RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline] RIP: 0010:__lock_acquire+0x54/0x3ff0 kernel/locking/lockdep.c:3276 Code: 84 24 d0 01 00 00 48 c7 84 24 98 00 00 00 b3 8a b5 41 48 c7 84 24 a0 00 00 00 78 29 b7 89 48 c7 84 24 a8 00 00 00 e0 f7 4a 81 <65> 4c 8b 2c 25 c0 df 01 00 48 89 04 24 48 8d 84 24 98 00 00 00 48 RSP: 0018:ffff8880488ef500 EFLAGS: 00000086 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: dffffc0000000000 RSI: 0000000000000000 RDI: ffff88809db08548 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000005 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: ffff88809db08548 R15: 0000000000000001 FS: 00007f51e9acb700(0000) GS:ffff8880ba000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020200030 CR3: 000000004467c000 CR4: 00000000003406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908 __mutex_lock_common kernel/locking/mutex.c:937 [inline] __mutex_lock+0xd7/0x1190 kernel/locking/mutex.c:1078 unix_dgram_recvmsg+0x23a/0xdb0 net/unix/af_unix.c:2142 ___sys_recvmsg+0x255/0x570 net/socket.c:2389 __sys_recvmmsg+0x254/0x6d0 net/socket.c:2501 do_sys_recvmmsg+0x172/0x190 net/socket.c:2577 __do_sys_recvmmsg net/socket.c:2595 [inline] __se_sys_recvmmsg net/socket.c:2591 [inline] __x64_sys_recvmmsg+0xba/0x150 net/socket.c:2591 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f51eb57a0f9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f51e9acb168 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007f51eb69a050 RCX: 00007f51eb57a0f9 RDX: 0000000000010106 RSI: 00000000200000c0 RDI: 0000000000000007 RBP: 00007f51eb5d5ae9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe62e4328f R14: 00007f51e9acb300 R15: 0000000000022000