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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_balance_workfn

read-write to 0xffffffff88bdf3ac of 4 bytes by task 3344 on cpu 0:
 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 0xffffffff88bdf3ac of 4 bytes by task 3265 on cpu 1:
 pcpu_alloc_noprof+0x9a7/0x10c0 mm/percpu.c:1894
 fib_nh_common_init+0x4a/0x2b0 net/ipv4/fib_semantics.c:590
 fib_nh_init+0x64/0x1b0 net/ipv4/fib_semantics.c:629
 fib_create_info+0xa1f/0x14f0 net/ipv4/fib_semantics.c:1495
 fib_table_insert+0x101/0xfa0 net/ipv4/fib_trie.c:1237
 fib_magic+0x1a1/0x1f0 net/ipv4/fib_frontend.c:1104
 fib_add_ifaddr+0xd5/0x330 net/ipv4/fib_frontend.c:1126
 fib_inetaddr_event+0xb9/0x200 net/ipv4/fib_frontend.c:1440
 notifier_call_chain kernel/notifier.c:93 [inline]
 blocking_notifier_call_chain+0x94/0x200 kernel/notifier.c:388
 __inet_insert_ifa+0x4cc/0x5e0 net/ipv4/devinet.c:571
 inet_rtm_newaddr+0x8d8/0xc30 net/ipv4/devinet.c:982
 rtnetlink_rcv_msg+0x6aa/0x710 net/core/rtnetlink.c:6646
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2550
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6664
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x599/0x670 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x5cc/0x6e0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:744
 __sys_sendto+0x1d6/0x260 net/socket.c:2209
 __do_sys_sendto net/socket.c:2221 [inline]
 __se_sys_sendto net/socket.c:2217 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2217
 x64_sys_call+0x2959/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:45
 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 -> 0xfffffffc

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3265 Comm: syz-executor Not tainted 6.12.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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