====================================================== WARNING: possible circular locking dependency detected 4.19.142-syzkaller #0 Not tainted ------------------------------------------------------ kworker/u4:1/30294 is trying to acquire lock: 00000000db0c3de4 (&qdisc_tx_lock){+.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] 00000000db0c3de4 (&qdisc_tx_lock){+.-.}, at: red_adaptative_timer+0x92/0x5c0 net/sched/sch_red.c:265 but task is already holding lock: 00000000e9f33647 ((&q->adapt_timer)){+.-.}, at: lockdep_copy_map include/linux/lockdep.h:168 [inline] 00000000e9f33647 ((&q->adapt_timer)){+.-.}, at: call_timer_fn+0xc9/0x700 kernel/time/timer.c:1328 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 ((&q->adapt_timer)){+.-.}: red_destroy+0x15/0x60 net/sched/sch_red.c:182 qdisc_destroy+0x180/0x780 net/sched/sch_generic.c:983 red_change+0x514/0x1080 net/sched/sch_red.c:236 qdisc_change net/sched/sch_api.c:1239 [inline] tc_modify_qdisc+0xf6a/0x1a80 net/sched/sch_api.c:1542 rtnetlink_rcv_msg+0x453/0xb80 net/core/rtnetlink.c:4778 netlink_rcv_skb+0x160/0x440 net/netlink/af_netlink.c:2455 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x4d5/0x690 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x6bb/0xc40 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xc3/0x120 net/socket.c:632 ___sys_sendmsg+0x7bb/0x8e0 net/socket.c:2115 __sys_sendmsg net/socket.c:2153 [inline] __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x132/0x220 net/socket.c:2160 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&qdisc_tx_lock){+.-.}: __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] red_adaptative_timer+0x92/0x5c0 net/sched/sch_red.c:265 call_timer_fn+0x177/0x700 kernel/time/timer.c:1338 expire_timers+0x243/0x4e0 kernel/time/timer.c:1375 __run_timers kernel/time/timer.c:1703 [inline] run_timer_softirq+0x21c/0x670 kernel/time/timer.c:1716 __do_softirq+0x26c/0x9a0 kernel/softirq.c:292 invoke_softirq kernel/softirq.c:372 [inline] irq_exit+0x215/0x260 kernel/softirq.c:412 exiting_irq arch/x86/include/asm/apic.h:544 [inline] smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1094 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 debug_lockdep_rcu_enabled+0xac/0xe0 kernel/rcu/update.c:255 rcu_read_lock include/linux/rcupdate.h:628 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:419 [inline] batadv_nc_worker+0x132/0xd50 net/batman-adv/network-coding.c:730 process_one_work+0x864/0x1570 kernel/workqueue.c:2155 worker_thread+0x64c/0x1130 kernel/workqueue.c:2298 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((&q->adapt_timer)); lock(&qdisc_tx_lock); lock((&q->adapt_timer)); lock(&qdisc_tx_lock); *** DEADLOCK *** 4 locks held by kworker/u4:1/30294: #0: 0000000005cb5aba ((wq_completion)"%s""bat_events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2126 #1: 00000000d38aeb13 ((work_completion)(&(&bat_priv->nc.work)->work)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2130 #2: 00000000c7bd8bbe (rcu_read_lock){....}, at: batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:417 [inline] #2: 00000000c7bd8bbe (rcu_read_lock){....}, at: batadv_nc_worker+0xf3/0xd50 net/batman-adv/network-coding.c:730 #3: 00000000e9f33647 ((&q->adapt_timer)){+.-.}, at: lockdep_copy_map include/linux/lockdep.h:168 [inline] #3: 00000000e9f33647 ((&q->adapt_timer)){+.-.}, at: call_timer_fn+0xc9/0x700 kernel/time/timer.c:1328 stack backtrace: CPU: 0 PID: 30294 Comm: kworker/u4:1 Not tainted 4.19.142-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fc/0x2fe lib/dump_stack.c:118 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1221 check_prev_add kernel/locking/lockdep.c:1865 [inline] check_prevs_add kernel/locking/lockdep.c:1978 [inline] validate_chain kernel/locking/lockdep.c:2419 [inline] __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3415 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3907 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144 spin_lock include/linux/spinlock.h:329 [inline] red_adaptative_timer+0x92/0x5c0 net/sched/sch_red.c:265 call_timer_fn+0x177/0x700 kernel/time/timer.c:1338 expire_timers+0x243/0x4e0 kernel/time/timer.c:1375 __run_timers kernel/time/timer.c:1703 [inline] run_timer_softirq+0x21c/0x670 kernel/time/timer.c:1716 __do_softirq+0x26c/0x9a0 kernel/softirq.c:292 invoke_softirq kernel/softirq.c:372 [inline] irq_exit+0x215/0x260 kernel/softirq.c:412 exiting_irq arch/x86/include/asm/apic.h:544 [inline] smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1094 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894 RIP: 0010:debug_lockdep_rcu_enabled kernel/rcu/update.c:253 [inline] RIP: 0010:debug_lockdep_rcu_enabled+0xac/0xe0 kernel/rcu/update.c:251 Code: 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 32 8b 93 84 08 00 00 31 c0 5b <85> d2 0f 94 c0 c3 31 c0 5b c3 48 c7 c7 44 84 ae 89 e8 2e 58 48 00 RSP: 0018:ffff8881c6437ca0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000000 RBX: ffff888050819ee0 RCX: 0000000000000001 RDX: 0000000000000000 RSI: 0000000000000002 RDI: ffff8881c5e72b84 RBP: 0000000000000001 R08: 000000008c9d5292 R09: 0000000000000002 R10: ffff8881c5e72bd8 R11: 0000000000000000 R12: 0000000000000000 R13: dffffc0000000000 R14: 00000000000001cc R15: ffff88809a5de400 rcu_read_lock include/linux/rcupdate.h:628 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:419 [inline] batadv_nc_worker+0x132/0xd50 net/batman-adv/network-coding.c:730 process_one_work+0x864/0x1570 kernel/workqueue.c:2155 worker_thread+0x64c/0x1130 kernel/workqueue.c:2298 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 xt_nfacct: accounting object `syz0' does not exists xt_nfacct: accounting object `syz0' does not exists xt_nfacct: accounting object `syz0' does not exists