syzbot

IPVS: ftp: loaded support on port[0] = 21
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BUG: KCSAN: data-race in pcpu_alloc / pcpu_balance_workfn

write to 0xffffffff8952501c of 4 bytes by task 12 on cpu 0:
 pcpu_update_empty_pages mm/percpu.c:558 [inline]
 pcpu_chunk_populated mm/percpu.c:1492 [inline]
 __pcpu_balance_workfn mm/percpu.c:2033 [inline]
 pcpu_balance_workfn+0xc6c/0xe30 mm/percpu.c:2069
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffffffff8952501c of 4 bytes by task 15306 on cpu 1:
 pcpu_alloc+0xb36/0x1370 mm/percpu.c:1835
 __alloc_percpu+0x20/0x30 mm/percpu.c:1907
 ipv6_init_mibs net/ipv6/af_inet6.c:900 [inline]
 inet6_net_init+0x284/0x440 net/ipv6/af_inet6.c:958
 ops_init+0x1e8/0x230 net/core/net_namespace.c:151
 setup_net+0x11b/0x630 net/core/net_namespace.c:341
 copy_net_ns+0x24c/0x390 net/core/net_namespace.c:482
 create_new_namespaces+0x216/0x520 kernel/nsproxy.c:110
 copy_namespaces+0x114/0x180 kernel/nsproxy.c:179
 copy_process+0x12ce/0x2dc0 kernel/fork.c:2072
 _do_fork+0x14a/0x6c0 kernel/fork.c:2428
 __do_sys_clone kernel/fork.c:2545 [inline]
 __se_sys_clone kernel/fork.c:2529 [inline]
 __x64_sys_clone+0xc8/0xf0 kernel/fork.c:2529
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15306 Comm: syz-executor.2 Not tainted 5.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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