syzbot

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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_balance_workfn

read-write to 0xffffffff88bec32c of 4 bytes by task 3381 on cpu 1:
 pcpu_update_empty_pages mm/percpu.c:602 [inline]
 pcpu_chunk_populated mm/percpu.c:1531 [inline]
 pcpu_balance_populated mm/percpu.c:2062 [inline]
 pcpu_balance_workfn+0x94e/0xa60 mm/percpu.c:2212
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffffff88bec32c of 4 bytes by task 3315 on cpu 0:
 pcpu_alloc_noprof+0x9b6/0x10a0 mm/percpu.c:1894
 xt_percpu_counter_alloc+0x79/0x110 net/netfilter/x_tables.c:1931
 find_check_entry net/ipv4/netfilter/ip_tables.c:526 [inline]
 translate_table+0x921/0xf70 net/ipv4/netfilter/ip_tables.c:716
 do_replace net/ipv4/netfilter/ip_tables.c:1137 [inline]
 do_ipt_set_ctl+0x7bd/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:4029
 sock_common_setsockopt+0x64/0x80 net/core/sock.c:3809
 do_sock_setsockopt net/socket.c:2311 [inline]
 __sys_setsockopt+0x187/0x200 net/socket.c:2336
 __do_sys_setsockopt net/socket.c:2342 [inline]
 __se_sys_setsockopt net/socket.c:2339 [inline]
 __x64_sys_setsockopt+0x66/0x80 net/socket.c:2339
 x64_sys_call+0x282e/0x2dc0 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

value changed: 0x00000001 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3315 Comm: syz-executor Not tainted 6.12.0-syzkaller-01782-gbf9aa14fc523 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
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EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000.