================================================================== BUG: KCSAN: data-race in pcpu_alloc / pcpu_free_area write to 0xffffffff8455e78c of 4 bytes by task 1752 on cpu 0: pcpu_update_empty_pages mm/percpu.c:559 [inline] pcpu_block_update_hint_free mm/percpu.c:994 [inline] pcpu_free_area+0x531/0x5e0 mm/percpu.c:1254 free_percpu+0x1d2/0x690 mm/percpu.c:2102 xt_percpu_counter_free+0x5f/0x70 net/netfilter/x_tables.c:1889 cleanup_entry+0x15a/0x180 net/ipv4/netfilter/ip_tables.c:655 __do_replace+0x45e/0x580 net/ipv4/netfilter/ip_tables.c:1084 do_replace net/ipv4/netfilter/ip_tables.c:1139 [inline] do_ipt_set_ctl+0x6ac/0x1630 net/ipv4/netfilter/ip_tables.c:1629 nf_setsockopt+0x1a6/0x1c0 net/netfilter/nf_sockopt.c:101 ip_setsockopt+0x2602/0x2a20 net/ipv4/ip_sockglue.c:1435 tcp_setsockopt+0x8c/0xa0 net/ipv4/tcp.c:3655 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3257 __sys_setsockopt+0x18f/0x200 net/socket.c:2117 __do_sys_setsockopt net/socket.c:2128 [inline] __se_sys_setsockopt net/socket.c:2125 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2125 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffffffff8455e78c of 4 bytes by task 21533 on cpu 1: pcpu_alloc+0x9d6/0x1170 mm/percpu.c:1835 __alloc_percpu+0x20/0x30 mm/percpu.c:1907 alloc_vfsmnt+0xcf/0x2e0 fs/namespace.c:212 clone_mnt+0x40/0x8e0 fs/namespace.c:1054 copy_tree+0x30e/0x910 fs/namespace.c:1875 copy_mnt_ns+0x11d/0x870 fs/namespace.c:3345 create_new_namespaces+0x89/0x560 kernel/nsproxy.c:78 unshare_nsproxy_namespaces+0xe2/0x120 kernel/nsproxy.c:226 ksys_unshare+0x381/0x710 kernel/fork.c:3003 __do_sys_unshare kernel/fork.c:3071 [inline] __se_sys_unshare kernel/fork.c:3069 [inline] __x64_sys_unshare+0x1b/0x20 kernel/fork.c:3069 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 21533 Comm: syz-executor.4 Tainted: G W 5.12.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ==================================================================