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BUG: KCSAN: data-race in pcpu_alloc / pcpu_balance_workfn

read-write to 0xffffffff86e8f9bc of 4 bytes by task 34 on cpu 0:
 pcpu_update_empty_pages mm/percpu.c:606 [inline]
 pcpu_chunk_populated mm/percpu.c:1534 [inline]
 pcpu_balance_populated mm/percpu.c:2094 [inline]
 pcpu_balance_workfn+0xb27/0xce0 mm/percpu.c:2245
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

read to 0xffffffff86e8f9bc of 4 bytes by task 1821 on cpu 1:
 pcpu_alloc+0x9bb/0xfb0 mm/percpu.c:1877
 __alloc_percpu+0x20/0x30 mm/percpu.c:1949
 xt_percpu_counter_alloc+0x6e/0x110 net/netfilter/x_tables.c:1930
 find_check_entry net/ipv4/netfilter/ip_tables.c:528 [inline]
 translate_table+0x96c/0xfb0 net/ipv4/netfilter/ip_tables.c:718
 ipt_register_table+0x95/0x3d0 net/ipv4/netfilter/ip_tables.c:1737
 iptable_filter_table_init+0x84/0xb0 net/ipv4/netfilter/iptable_filter.c:49
 xt_find_table_lock+0x1c9/0x2d0 net/netfilter/x_tables.c:1259
 xt_request_find_table_lock+0x22/0xa0 net/netfilter/x_tables.c:1284
 get_info net/ipv4/netfilter/ip_tables.c:965 [inline]
 do_ipt_get_ctl+0x53b/0xbd0 net/ipv4/netfilter/ip_tables.c:1654
 nf_getsockopt+0x18f/0x1b0 net/netfilter/nf_sockopt.c:116
 ip_getsockopt+0xc33/0xe20 net/ipv4/ip_sockglue.c:1786
 tcp_getsockopt+0xe8/0x18d0 net/ipv4/tcp.c:4295
 sock_common_getsockopt+0x53/0x60 net/core/sock.c:3478
 __sys_getsockopt+0x17a/0x1e0 net/socket.c:2224
 __do_sys_getsockopt net/socket.c:2239 [inline]
 __se_sys_getsockopt net/socket.c:2236 [inline]
 __x64_sys_getsockopt+0x62/0x70 net/socket.c:2236
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000001 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1821 Comm: syz-executor.0 Not tainted 5.18.0-rc5-syzkaller-00163-g4b97bac0756a-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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