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BUG: KCSAN: data-race in copy_mm / percpu_counter_destroy_many

write to 0xffff88810ce9cb78 of 8 bytes by task 14900 on cpu 0:
 __list_del include/linux/list.h:226 [inline]
 __list_del_entry include/linux/list.h:249 [inline]
 list_del include/linux/list.h:260 [inline]
 percpu_counter_destroy_many+0xbd/0x320 lib/percpu_counter.c:244
 __mmdrop+0x1ef/0x370 kernel/fork.c:740
 mmdrop include/linux/sched/mm.h:55 [inline]
 mmdrop_sched include/linux/sched/mm.h:83 [inline]
 mmdrop_lazy_tlb_sched include/linux/sched/mm.h:110 [inline]
 finish_task_switch+0x294/0x340 kernel/sched/core.c:5392
 context_switch kernel/sched/core.c:5513 [inline]
 __schedule+0x799/0xd10 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x5a/0xa0 kernel/sched/core.c:7326
 schedule_timeout+0x53/0x180 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common kernel/sched/completion.c:121 [inline]
 wait_for_common+0xef/0x1d0 kernel/sched/completion.c:132
 wait_for_completion_state+0x15/0x40 kernel/sched/completion.c:269
 call_usermodehelper_exec+0x270/0x2c0 kernel/umh.c:441
 call_modprobe kernel/module/kmod.c:103 [inline]
 __request_module+0x283/0x3c0 kernel/module/kmod.c:173
 dev_load+0x61/0xc0 net/core/dev_ioctl.c:674
 dev_ioctl+0x4fe/0x960 net/core/dev_ioctl.c:741
 sock_do_ioctl+0x1aa/0x230 net/socket.c:1314
 sock_ioctl+0x439/0x610 net/socket.c:1421
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810ce9c600 of 1728 bytes by task 15081 on cpu 1:
 dup_mm kernel/fork.c:1537 [inline]
 copy_mm+0xd6/0x340 kernel/fork.c:1595
 copy_process+0x108c/0x2310 kernel/fork.c:2289
 kernel_clone+0x1c0/0x5f0 kernel/fork.c:2748
 __do_sys_clone kernel/fork.c:2889 [inline]
 __se_sys_clone kernel/fork.c:2873 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2873
 x64_sys_call+0x1222/0x3020 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 15081 Comm: dhcpcd-run-hook Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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