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BUG: KCSAN: data-race in pcpu_alloc / pcpu_alloc

read-write to 0xffffffff86ea39bc of 4 bytes by task 9997 on cpu 1:
 pcpu_reintegrate_chunk mm/percpu.c:588 [inline]
 pcpu_alloc+0x6e2/0x1020 mm/percpu.c:1815
 __alloc_percpu_gfp+0x22/0x30 mm/percpu.c:1937
 bpf_map_alloc_percpu+0xab/0x120 kernel/bpf/syscall.c:462
 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/0x710 kernel/bpf/syscall.c:1082
 __sys_bpf+0x296/0x630 kernel/bpf/syscall.c:4899
 __do_sys_bpf kernel/bpf/syscall.c:5021 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5019 [inline]
 __x64_sys_bpf+0x3f/0x50 kernel/bpf/syscall.c:5019
 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 0xffffffff86ea39bc of 4 bytes by task 10007 on cpu 0:
 pcpu_alloc+0x9cb/0x1020 mm/percpu.c:1877
 __alloc_percpu+0x20/0x30 mm/percpu.c:1950
 ipv6_init_mibs net/ipv6/af_inet6.c:903 [inline]
 inet6_net_init+0x218/0x440 net/ipv6/af_inet6.c:979
 ops_init+0x1f1/0x240 net/core/net_namespace.c:134
 setup_net+0x2cb/0x810 net/core/net_namespace.c:325
 copy_net_ns+0x2a2/0x440 net/core/net_namespace.c:471
 create_new_namespaces+0x22c/0x450 kernel/nsproxy.c:110
 copy_namespaces+0x116/0x160 kernel/nsproxy.c:178
 copy_process+0xdc2/0x20b0 kernel/fork.c:2243
 kernel_clone+0x163/0x5c0 kernel/fork.c:2655
 __do_sys_clone kernel/fork.c:2789 [inline]
 __se_sys_clone kernel/fork.c:2773 [inline]
 __x64_sys_clone+0xc3/0xf0 kernel/fork.c:2773
 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: 0 PID: 10007 Comm: syz-executor.1 Not tainted 5.19.0-rc7-syzkaller-00139-g4ba1329cbb94-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
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