syzbot

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BUG: KCSAN: data-race in wq_worker_tick / wq_worker_tick

read-write to 0xffff8881000738b8 of 8 bytes by interrupt on cpu 1:
 wq_worker_tick+0x60/0x230 kernel/workqueue.c:1474
 sched_tick+0xd7/0x220 kernel/sched/core.c:5546
 update_process_times+0x15f/0x190 kernel/time/timer.c:2479
 tick_sched_handle kernel/time/tick-sched.c:298 [inline]
 tick_nohz_handler+0x276/0x3d0 kernel/time/tick-sched.c:319
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x20f/0x5a0 kernel/time/hrtimer.c:1841
 hrtimer_interrupt+0x21a/0x460 kernel/time/hrtimer.c:1903
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1d0 arch/x86/kernel/apic/apic.c:1062
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0x32/0x80 arch/x86/kernel/apic/apic.c:1056
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 is_atomic kernel/kcsan/core.c:260 [inline]
 should_watch kernel/kcsan/core.c:277 [inline]
 check_access kernel/kcsan/core.c:752 [inline]
 __tsan_read1+0xf8/0x180 kernel/kcsan/core.c:1022
 __nf_ct_ext_exist include/net/netfilter/nf_conntrack_extend.h:47 [inline]
 nf_ct_ext_find include/net/netfilter/nf_conntrack_extend.h:61 [inline]
 nfct_nat include/net/netfilter/nf_nat.h:51 [inline]
 nf_nat_inet_fn+0x10d/0x690 net/netfilter/nf_nat_core.c:922
 nf_nat_ipv4_fn net/netfilter/nf_nat_proto.c:602 [inline]
 nf_nat_ipv4_pre_routing+0x124/0x210 net/netfilter/nf_nat_proto.c:612
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0x78/0x180 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK include/linux/netfilter.h:316 [inline]
 ip_rcv+0xfe/0x140 net/ipv4/ip_input.c:573
 __netif_receive_skb_one_core net/core/dev.c:6139 [inline]
 __netif_receive_skb+0xff/0x270 net/core/dev.c:6252
 process_backlog+0x228/0x420 net/core/dev.c:6604
 __napi_poll+0x5f/0x300 net/core/dev.c:7668
 napi_poll net/core/dev.c:7731 [inline]
 net_rx_action+0x425/0x8c0 net/core/dev.c:7883
 handle_softirqs+0xba/0x290 kernel/softirq.c:622
 do_softirq+0x45/0x60 kernel/softirq.c:523
 __local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 __alloc_skb+0x476/0x4b0 net/core/skbuff.c:674
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:818 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:875 [inline]
 nsim_dev_trap_report_work+0x18a/0x630 drivers/net/netdevsim/dev.c:921
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read-write to 0xffff8881000738b8 of 8 bytes by interrupt on cpu 0:
 wq_worker_tick+0x60/0x230 kernel/workqueue.c:1474
 sched_tick+0xd7/0x220 kernel/sched/core.c:5546
 update_process_times+0x15f/0x190 kernel/time/timer.c:2479
 tick_sched_handle kernel/time/tick-sched.c:298 [inline]
 tick_nohz_handler+0x276/0x3d0 kernel/time/tick-sched.c:319
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x20f/0x5a0 kernel/time/hrtimer.c:1841
 hrtimer_interrupt+0x21a/0x460 kernel/time/hrtimer.c:1903
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1d0 arch/x86/kernel/apic/apic.c:1062
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0x32/0x80 arch/x86/kernel/apic/apic.c:1056
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 kcsan_setup_watchpoint+0x406/0x420 kernel/kcsan/core.c:705
 ipt_do_table+0x1d3/0xab0 net/ipv4/netfilter/ip_tables.c:263
 ipt_mangle_out net/ipv4/netfilter/iptable_mangle.c:53 [inline]
 iptable_mangle_hook+0xd6/0x260 net/ipv4/netfilter/iptable_mangle.c:79
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0x78/0x180 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 __ip_local_out+0x2cb/0x2f0 net/ipv4/ip_output.c:120
 ip_local_out+0x2a/0xe0 net/ipv4/ip_output.c:129
 synproxy_send_tcp+0x2ae/0x2f0 net/netfilter/nf_synproxy_core.c:439
 synproxy_send_client_synack+0x57c/0x5d0 net/netfilter/nf_synproxy_core.c:484
 nft_synproxy_eval_v4+0x22a/0x280 net/netfilter/nft_synproxy.c:59
 nft_synproxy_do_eval+0x1cf/0x270 net/netfilter/nft_synproxy.c:141
 nft_synproxy_eval+0x29/0x40 net/netfilter/nft_synproxy.c:247
 expr_call_ops_eval net/netfilter/nf_tables_core.c:237 [inline]
 nft_do_chain+0x1e2/0xc90 net/netfilter/nf_tables_core.c:285
 nft_do_chain_inet+0x1eb/0x220 net/netfilter/nft_chain_filter.c:161
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0x78/0x180 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK include/linux/netfilter.h:316 [inline]
 ip_local_deliver+0x178/0x1c0 net/ipv4/ip_input.c:262
 dst_input include/net/dst.h:474 [inline]
 ip_rcv_finish+0x194/0x1c0 net/ipv4/ip_input.c:453
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip_rcv+0x62/0x140 net/ipv4/ip_input.c:573
 __netif_receive_skb_one_core net/core/dev.c:6139 [inline]
 __netif_receive_skb+0xff/0x270 net/core/dev.c:6252
 process_backlog+0x228/0x420 net/core/dev.c:6604
 __napi_poll+0x5f/0x300 net/core/dev.c:7668
 napi_poll net/core/dev.c:7731 [inline]
 net_rx_action+0x425/0x8c0 net/core/dev.c:7883
 handle_softirqs+0xba/0x290 kernel/softirq.c:622
 do_softirq+0x45/0x60 kernel/softirq.c:523
 __local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 __alloc_skb+0x476/0x4b0 net/core/skbuff.c:674
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:818 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:875 [inline]
 nsim_dev_trap_report_work+0x18a/0x630 drivers/net/netdevsim/dev.c:921
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x00000000053aa750 -> 0x00000000053ace60

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 41 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound nsim_dev_trap_report_work
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