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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_free_area

read-write to 0xffffffff88be03ac of 4 bytes by task 36 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+0x186/0x1b0 net/ipv4/netfilter/ip_tables.c:654
 __ipt_unregister_table net/ipv4/netfilter/ip_tables.c:1717 [inline]
 ipt_unregister_table_exit+0x77/0x110 net/ipv4/netfilter/ip_tables.c:1805
 iptable_raw_net_exit+0x1c/0x30 net/ipv4/netfilter/iptable_raw.c:61
 ops_exit_list net/core/net_namespace.c:173 [inline]
 cleanup_net+0x475/0x810 net/core/net_namespace.c:626
 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 0xffffffff88be03ac of 4 bytes by task 5198 on cpu 1:
 pcpu_alloc_noprof+0x9b6/0x10a0 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:586
 inet_rtm_newaddr+0x8d8/0xc30 net/ipv4/devinet.c:997
 rtnetlink_rcv_msg+0x6aa/0x710 net/core/rtnetlink.c:6675
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2551
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6693
 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:2214
 __do_sys_sendto net/socket.c:2226 [inline]
 __se_sys_sendto net/socket.c:2222 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2222
 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: 0x00000083 -> 0x00000084

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5198 Comm: syz-executor Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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