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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_free_area

read-write to 0xffffffff88bdd3ac of 4 bytes by task 10459 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+0x4dc/0x570 mm/percpu.c:1302
 free_percpu+0x1c6/0xb30 mm/percpu.c:2246
 xt_percpu_counter_free+0x63/0x80 net/netfilter/x_tables.c:1951
 cleanup_entry+0x195/0x1c0 net/ipv6/netfilter/ip6_tables.c:671
 __do_replace+0x470/0x580 net/ipv6/netfilter/ip6_tables.c:1099
 do_replace net/ipv6/netfilter/ip6_tables.c:1158 [inline]
 do_ip6t_set_ctl+0x820/0x8c0 net/ipv6/netfilter/ip6_tables.c:1644
 nf_setsockopt+0x195/0x1b0 net/netfilter/nf_sockopt.c:101
 ipv6_setsockopt+0x10f/0x130 net/ipv6/ipv6_sockglue.c:998
 tcp_setsockopt+0x93/0xb0 net/ipv4/tcp.c:4029
 sock_common_setsockopt+0x64/0x80 net/core/sock.c:3803
 do_sock_setsockopt net/socket.c:2329 [inline]
 __sys_setsockopt+0x1cc/0x240 net/socket.c:2352
 __do_sys_setsockopt net/socket.c:2361 [inline]
 __se_sys_setsockopt net/socket.c:2358 [inline]
 __x64_sys_setsockopt+0x66/0x80 net/socket.c:2358
 x64_sys_call+0x278d/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:55
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88bdd3ac of 4 bytes by task 12463 on cpu 1:
 pcpu_alloc_noprof+0x9a7/0x10c0 mm/percpu.c:1894
 gro_cells_init+0x31/0x170 net/core/gro_cells.c:74
 ip_tunnel_init+0x8b/0x180 net/ipv4/ip_tunnel.c:1322
 ipgre_tunnel_init+0x388/0x3b0 net/ipv4/ip_gre.c:1049
 register_netdevice+0x293/0xe30 net/core/dev.c:10418
 __ip_tunnel_create+0x1c5/0x270 net/ipv4/ip_tunnel.c:267
 ip_tunnel_init_net+0x18a/0x3e0 net/ipv4/ip_tunnel.c:1160
 ipgre_init_net+0x30/0x40 net/ipv4/ip_gre.c:1059
 ops_init+0x1c9/0x260 net/core/net_namespace.c:139
 setup_net+0x14d/0x600 net/core/net_namespace.c:356
 copy_net_ns+0x290/0x430 net/core/net_namespace.c:494
 create_new_namespaces+0x228/0x430 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xe6/0x120 kernel/nsproxy.c:228
 ksys_unshare+0x3c9/0x6e0 kernel/fork.c:3311
 __do_sys_unshare kernel/fork.c:3382 [inline]
 __se_sys_unshare kernel/fork.c:3380 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3380
 x64_sys_call+0x2c8d/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:273
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000041 -> 0x00000042

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12463 Comm: syz.2.3059 Tainted: G        W          6.12.0-rc1-syzkaller-00257-g2f91ff27b0ee #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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