syzbot

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BUG: KCSAN: data-race in pcpu_alloc / pcpu_block_update_hint_alloc

read-write to 0xffffffff8842949c of 4 bytes by task 24407 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+0x49f/0x4d0 mm/percpu.c:1258
 pcpu_alloc+0x4b3/0x10d0 mm/percpu.c:1808
 __alloc_percpu_gfp+0x26/0x30 mm/percpu.c:1930
 bpf_map_alloc_percpu+0xab/0x200 kernel/bpf/syscall.c:466
 prealloc_init+0x19f/0x470 kernel/bpf/hashtab.c:341
 htab_map_alloc+0x637/0x8f0 kernel/bpf/hashtab.c:576
 map_create+0x83c/0xb90 kernel/bpf/syscall.c:1333
 __sys_bpf+0x667/0x7a0 kernel/bpf/syscall.c:5669
 __do_sys_bpf kernel/bpf/syscall.c:5794 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5792 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5792
 x64_sys_call+0x86c/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8842949c of 4 bytes by task 24409 on cpu 1:
 pcpu_alloc+0x9aa/0x10d0 mm/percpu.c:1868
 __alloc_percpu_gfp+0x26/0x30 mm/percpu.c:1930
 bpf_map_alloc_percpu+0xab/0x200 kernel/bpf/syscall.c:466
 prealloc_init+0x19f/0x470 kernel/bpf/hashtab.c:341
 htab_map_alloc+0x637/0x8f0 kernel/bpf/hashtab.c:576
 map_create+0x83c/0xb90 kernel/bpf/syscall.c:1333
 __sys_bpf+0x667/0x7a0 kernel/bpf/syscall.c:5669
 __do_sys_bpf kernel/bpf/syscall.c:5794 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5792 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5792
 x64_sys_call+0x86c/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000002 -> 0xfffffffa

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24409 Comm: syz-executor.4 Not tainted 6.9.0-syzkaller-08414-g7ee332c9f12b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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