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BUG: KCSAN: data-race in copy_mm / percpu_counter_destroy_many

write to 0xffff88811e8e9a78 of 8 bytes by task 28641 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+0x222/0x320 kernel/sched/core.c:5386
 context_switch kernel/sched/core.c:5507 [inline]
 __schedule+0x799/0xd10 kernel/sched/core.c:7228
 preempt_schedule_irq+0x2d/0x50 kernel/sched/core.c:7552
 raw_irqentry_exit_cond_resched+0x4b/0x60 kernel/entry/common.c:145
 irqentry_exit_to_kernel_mode_preempt+0x2b/0x40 include/linux/irq-entry-common.h:468
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x7d/0x610 kernel/entry/common.c:167
 sysvec_apic_timer_interrupt+0x44/0x80 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
 check_access kernel/kcsan/core.c:752 [inline]
 __tsan_unaligned_write1+0x14d/0x180 kernel/kcsan/core.c:1022
 mas_dup_build+0x38c/0xe80 lib/maple_tree.c:6119
 __mt_dup+0x109/0x1d0 lib/maple_tree.c:6159
 dup_mmap+0x277/0x10b0 mm/mmap.c:1757
 dup_mm kernel/fork.c:1538 [inline]
 copy_mm+0xfa/0x340 kernel/fork.c:1590
 copy_process+0x10cd/0x2350 kernel/fork.c:2288
 kernel_clone+0x1c0/0x5f0 kernel/fork.c:2746
 __do_sys_clone kernel/fork.c:2887 [inline]
 __se_sys_clone kernel/fork.c:2871 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2871
 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

read to 0xffff88811e8e9500 of 1728 bytes by task 28647 on cpu 1:
 dup_mm kernel/fork.c:1532 [inline]
 copy_mm+0xd6/0x340 kernel/fork.c:1590
 copy_process+0x10cd/0x2350 kernel/fork.c:2288
 kernel_clone+0x1c0/0x5f0 kernel/fork.c:2746
 __do_sys_clone kernel/fork.c:2887 [inline]
 __se_sys_clone kernel/fork.c:2871 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2871
 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: 28647 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 05/09/2026
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