syzbot

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BUG: KCSAN: data-race in pcpu_alloc / pcpu_alloc

read-write to 0xffffffff870c39b4 of 4 bytes by task 24285 on cpu 0:
 pcpu_reintegrate_chunk mm/percpu.c:588 [inline]
 pcpu_alloc+0x6e2/0x1040 mm/percpu.c:1815
 __alloc_percpu_gfp+0x22/0x30 mm/percpu.c:1937
 bpf_map_alloc_percpu+0xbd/0x200 kernel/bpf/syscall.c:481
 prealloc_init kernel/bpf/hashtab.c:346 [inline]
 htab_map_alloc+0x76e/0xc00 kernel/bpf/hashtab.c:558
 find_and_alloc_map kernel/bpf/syscall.c:131 [inline]
 map_create+0x38a/0x6f0 kernel/bpf/syscall.c:1102
 __sys_bpf+0x296/0x630 kernel/bpf/syscall.c:4936
 __do_sys_bpf kernel/bpf/syscall.c:5058 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5056 [inline]
 __x64_sys_bpf+0x3f/0x50 kernel/bpf/syscall.c:5056
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffffff870c39b4 of 4 bytes by task 24274 on cpu 1:
 pcpu_alloc+0x9c6/0x1040 mm/percpu.c:1877
 __alloc_percpu_gfp+0x22/0x30 mm/percpu.c:1937
 bpf_map_alloc_percpu+0xbd/0x200 kernel/bpf/syscall.c:481
 prealloc_init kernel/bpf/hashtab.c:346 [inline]
 htab_map_alloc+0x76e/0xc00 kernel/bpf/hashtab.c:558
 find_and_alloc_map kernel/bpf/syscall.c:131 [inline]
 map_create+0x38a/0x6f0 kernel/bpf/syscall.c:1102
 __sys_bpf+0x296/0x630 kernel/bpf/syscall.c:4936
 __do_sys_bpf kernel/bpf/syscall.c:5058 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5056 [inline]
 __x64_sys_bpf+0x3f/0x50 kernel/bpf/syscall.c:5056
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000 -> 0xfffffff8

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24274 Comm: syz-executor.3 Not tainted 5.19.0-syzkaller-13215-geb555cb5b794-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
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