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BUG: KCSAN: data-race in pcpu_alloc / pcpu_free_area

read-write to 0xffffffff884054dc of 4 bytes by task 3097 on cpu 0:
 pcpu_update_empty_pages mm/percpu.c:602 [inline]
 pcpu_block_update_hint_free mm/percpu.c:1044 [inline]
 pcpu_free_area+0x4e2/0x570 mm/percpu.c:1302
 free_percpu+0x1c6/0xb30 mm/percpu.c:2303
 xt_percpu_counter_free+0x63/0x80 net/netfilter/x_tables.c:1951
 cleanup_entry+0x186/0x1b0 net/ipv4/netfilter/ip_tables.c:654
 __do_replace+0x46e/0x570 net/ipv4/netfilter/ip_tables.c:1082
 do_replace net/ipv4/netfilter/ip_tables.c:1141 [inline]
 do_ipt_set_ctl+0x811/0x8b0 net/ipv4/netfilter/ip_tables.c:1635
 nf_setsockopt+0x195/0x1b0 net/netfilter/nf_sockopt.c:101
 ip_setsockopt+0xea/0x100 net/ipv4/ip_sockglue.c:1424
 tcp_setsockopt+0x93/0xb0 net/ipv4/tcp.c:3737
 sock_common_setsockopt+0x64/0x80 net/core/sock.c:3727
 do_sock_setsockopt net/socket.c:2311 [inline]
 __sys_setsockopt+0x1d8/0x250 net/socket.c:2334
 __do_sys_setsockopt net/socket.c:2343 [inline]
 __se_sys_setsockopt net/socket.c:2340 [inline]
 __x64_sys_setsockopt+0x66/0x80 net/socket.c:2340
 x64_sys_call+0x1159/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:55
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff884054dc of 4 bytes by task 906 on cpu 1:
 pcpu_alloc+0x9aa/0x10d0 mm/percpu.c:1868
 __alloc_percpu_gfp+0x26/0x30 mm/percpu.c:1930
 fib_nh_common_init+0x48/0x2b0 net/ipv4/fib_semantics.c:591
 fib6_nh_init+0xdc3/0x15c0 net/ipv6/route.c:3620
 ip6_route_info_create+0x7b7/0xba0 net/ipv6/route.c:3807
 ip6_route_add+0x26/0x120 net/ipv6/route.c:3851
 addrconf_add_mroute net/ipv6/addrconf.c:2548 [inline]
 addrconf_add_dev+0x1c6/0x240 net/ipv6/addrconf.c:2566
 addrconf_dev_config net/ipv6/addrconf.c:3480 [inline]
 addrconf_init_auto_addrs+0x497/0x6b0 net/ipv6/addrconf.c:3568
 addrconf_notify+0x7ae/0x950 net/ipv6/addrconf.c:3741
 notifier_call_chain kernel/notifier.c:93 [inline]
 raw_notifier_call_chain+0x6f/0x1d0 kernel/notifier.c:461
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:1950
 netdev_state_change+0x80/0xc0 net/core/dev.c:1332
 linkwatch_do_dev+0xb9/0xf0 net/core/link_watch.c:177
 __linkwatch_run_queue+0x284/0x510 net/core/link_watch.c:234
 linkwatch_event+0x40/0x50 net/core/link_watch.c:277
 process_one_work kernel/workqueue.c:3267 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3348
 worker_thread+0x526/0x730 kernel/workqueue.c:3429
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x0000001d -> 0x0000001e

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 906 Comm: kworker/1:2 Not tainted 6.9.0-rc6-syzkaller-00131-gf03359bca01b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: events linkwatch_event
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