syzbot

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BUG: KCSAN: data-race in ktime_get_real_seconds / timekeeping_update_from_shadow

write to 0xffffffff893a8488 of 304 bytes by interrupt on cpu 0:
 timekeeping_update_from_shadow+0x40d/0x440 kernel/time/timekeeping.c:829
 __timekeeping_advance+0xa5d/0xc10 kernel/time/timekeeping.c:2532
 timekeeping_advance kernel/time/timekeeping.c:2540 [inline]
 update_wall_time+0x21/0x50 kernel/time/timekeeping.c:2550
 tick_do_update_jiffies64+0x169/0x1c0 kernel/time/tick-sched.c:149
 tick_sched_do_timer kernel/time/tick-sched.c:253 [inline]
 tick_nohz_handler+0x8d/0x3d0 kernel/time/tick-sched.c:312
 __run_hrtimer kernel/time/hrtimer.c:1930 [inline]
 __hrtimer_run_queues+0x276/0x4f0 kernel/time/hrtimer.c:1994
 hrtimer_interrupt+0x261/0x850 kernel/time/hrtimer.c:2113
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1c0 arch/x86/kernel/apic/apic.c:1067
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0x32/0x80 arch/x86/kernel/apic/apic.c:1061
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 check_access kernel/kcsan/core.c:747 [inline]
 __tsan_read8+0xb7/0x190 kernel/kcsan/core.c:1025
 ifname_compare_aligned include/linux/netfilter/x_tables.h:414 [inline]
 ip_packet_match net/ipv4/netfilter/ip_tables.c:57 [inline]
 ipt_do_table+0x3d8/0xb20 net/ipv4/netfilter/ip_tables.c:283
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0x78/0x180 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK include/linux/netfilter.h:316 [inline]
 ip_local_deliver+0x199/0x1e0 net/ipv4/ip_input.c:262
 dst_input include/net/dst.h:480 [inline]
 ip_rcv_finish+0x188/0x1a0 net/ipv4/ip_input.c:492
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip_rcv+0x62/0x160 net/ipv4/ip_input.c:612
 __netif_receive_skb_one_core net/core/dev.c:6202 [inline]
 __netif_receive_skb net/core/dev.c:6315 [inline]
 process_backlog+0x341/0x670 net/core/dev.c:6666
 __napi_poll+0x61/0x300 net/core/dev.c:7733
 napi_poll net/core/dev.c:7796 [inline]
 net_rx_action+0x452/0x930 net/core/dev.c:7953
 handle_softirqs+0xb9/0x280 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+0x658/0x690 net/core/skbuff.c:697
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:819 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
 nsim_dev_trap_report_work+0x18a/0x640 drivers/net/netdevsim/dev.c:922
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3397
 worker_thread+0x58a/0x780 kernel/workqueue.c:3478
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff893a84c0 of 8 bytes by task 26222 on cpu 1:
 ktime_get_real_seconds+0x15/0x30 kernel/time/timekeeping.c:1156
 xfrm_lookup_with_ifid+0x1327/0x1590 net/xfrm/xfrm_policy.c:3282
 xfrm_lookup net/xfrm/xfrm_policy.c:3336 [inline]
 xfrm_lookup_route+0x3a/0x110 net/xfrm/xfrm_policy.c:3347
 ip_route_output_flow+0xdb/0x110 net/ipv4/route.c:2939
 udp_sendmsg+0x1308/0x1500 net/ipv4/udp.c:1409
 inet_sendmsg+0xac/0xd0 net/ipv4/af_inet.c:866
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 ____sys_sendmsg+0x519/0x5b0 net/socket.c:2698
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2752
 __sys_sendmmsg+0x185/0x320 net/socket.c:2841
 __do_sys_sendmmsg net/socket.c:2868 [inline]
 __se_sys_sendmmsg net/socket.c:2865 [inline]
 __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2865
 x64_sys_call+0x27aa/0x3020 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000006a105d61 -> 0x000000006a105d62

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 26222 Comm: syz.4.7655 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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