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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_block_update_hint_alloc

read-write to 0xffffffff88be03ac of 4 bytes by task 3531 on cpu 0:
 pcpu_update_empty_pages mm/percpu.c:602 [inline]
 pcpu_block_update_hint_alloc+0x5db/0x6a0 mm/percpu.c:923
 pcpu_alloc_area+0x488/0x4b0 mm/percpu.c:1258
 pcpu_alloc_noprof+0x4bb/0x10a0 mm/percpu.c:1834
 sock_inuse_init_net+0x28/0x60 net/core/sock.c:3889
 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

read to 0xffffffff88be03ac of 4 bytes by task 3530 on cpu 1:
 pcpu_alloc_noprof+0x9b6/0x10a0 mm/percpu.c:1894
 sock_inuse_init_net+0x28/0x60 net/core/sock.c:3889
 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: 0x00000002 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3530 Comm: syz-executor Not tainted 6.12.0-rc5-syzkaller-00047-g4236f913808c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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