syzbot

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BUG: KCSAN: data-race in pcpu_alloc / pcpu_balance_workfn

read-write to 0xffffffff86f8615c of 4 bytes by task 3067 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:2088 [inline]
 pcpu_balance_workfn+0x96f/0xa80 mm/percpu.c:2238
 process_one_work+0x434/0x860 kernel/workqueue.c:2597
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2748
 kthread+0x1d7/0x210 kernel/kthread.c:389
 ret_from_fork+0x2e/0x40 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:296

read to 0xffffffff86f8615c of 4 bytes by task 4000 on cpu 0:
 pcpu_alloc+0xa59/0x1280 mm/percpu.c:1870
 __alloc_percpu_gfp+0x26/0x30 mm/percpu.c:1930
 bpf_map_alloc_percpu+0xaa/0x200 kernel/bpf/syscall.c:464
 htab_map_alloc+0x37b/0xde0 kernel/bpf/hashtab.c:521
 map_create+0x713/0xa60 kernel/bpf/syscall.c:1206
 __sys_bpf+0x62a/0x780 kernel/bpf/syscall.c:5119
 __do_sys_bpf kernel/bpf/syscall.c:5241 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5239 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5239
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000 -> 0xfffffffc

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4000 Comm: syz-executor.3 Not tainted 6.5.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023
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