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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_block_update_hint_alloc

read-write to 0xffffffff88bdf3ac of 4 bytes by task 8940 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
 bpf_map_alloc_percpu+0xad/0x210 kernel/bpf/syscall.c:466
 prealloc_init+0x19f/0x470 kernel/bpf/hashtab.c:341
 htab_map_alloc+0x630/0x8e0 kernel/bpf/hashtab.c:579
 map_create+0x850/0xb70 kernel/bpf/syscall.c:1341
 __sys_bpf+0x667/0x7a0 kernel/bpf/syscall.c:5635
 __do_sys_bpf kernel/bpf/syscall.c:5760 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5758 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5758
 x64_sys_call+0x2625/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:322
 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 0xffffffff88bdf3ac of 4 bytes by task 3316 on cpu 1:
 pcpu_alloc_noprof+0x9b6/0x10a0 mm/percpu.c:1894
 mm_alloc_cid_noprof include/linux/mm_types.h:1199 [inline]
 mm_init+0x47f/0x730 kernel/fork.c:1301
 dup_mm kernel/fork.c:1671 [inline]
 copy_mm+0x11e/0x10e0 kernel/fork.c:1723
 copy_process+0xd5b/0x1f90 kernel/fork.c:2372
 kernel_clone+0x167/0x5e0 kernel/fork.c:2784
 __do_sys_clone kernel/fork.c:2927 [inline]
 __se_sys_clone kernel/fork.c:2911 [inline]
 __x64_sys_clone+0xe8/0x120 kernel/fork.c:2911
 x64_sys_call+0x2d23/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:57
 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: 0x00000005 -> 0xfffffffd

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3316 Comm: syz-executor Not tainted 6.12.0-rc4-syzkaller-00161-gae90f6a6170d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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