syzbot

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BUG: KCSAN: data-race in pcpu_alloc / pcpu_balance_workfn

read-write to 0xffffffff86f545d4 of 4 bytes by task 883 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+0x3e6/0x750 kernel/workqueue.c:2390
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2537
 kthread+0x1d7/0x210 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

read to 0xffffffff86f545d4 of 4 bytes by task 26167 on cpu 0:
 pcpu_alloc+0xa59/0x1280 mm/percpu.c:1870
 __alloc_percpu_gfp+0x26/0x30 mm/percpu.c:1930
 __percpu_counter_init+0x47/0x130 lib/percpu_counter.c:162
 mm_init+0x44a/0x5e0 kernel/fork.c:1300
 dup_mm kernel/fork.c:1680 [inline]
 copy_mm+0x11c/0xf80 kernel/fork.c:1732
 copy_process+0x1008/0x21b0 kernel/fork.c:2498
 kernel_clone+0x169/0x560 kernel/fork.c:2908
 __do_sys_clone kernel/fork.c:3051 [inline]
 __se_sys_clone kernel/fork.c:3035 [inline]
 __x64_sys_clone+0xe8/0x120 kernel/fork.c:3035
 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: 0x00000001 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26167 Comm: syz-executor.4 Not tainted 6.3.0-syzkaller-10620-g33afd4b76393 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
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EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000.