syzbot

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BUG: KCSAN: data-race in copy_mm / percpu_counter_destroy_many

write to 0xffff8881059dd608 of 8 bytes by task 10641 on cpu 1:
 __list_del include/linux/list.h:203 [inline]
 __list_del_entry include/linux/list.h:226 [inline]
 list_del include/linux/list.h:237 [inline]
 percpu_counter_destroy_many+0xc7/0x2b0 lib/percpu_counter.c:244
 __mmdrop+0x25d/0x3f0 kernel/fork.c:735
 mmdrop include/linux/sched/mm.h:55 [inline]
 io_ring_ctx_free+0x414/0x460 io_uring/io_uring.c:2170
 io_ring_exit_work+0x508/0x530 io_uring/io_uring.c:2395
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0x4de/0x9e0 kernel/workqueue.c:3358
 worker_thread+0x581/0x770 kernel/workqueue.c:3439
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881059dd100 of 1664 bytes by task 15858 on cpu 0:
 dup_mm kernel/fork.c:1524 [inline]
 copy_mm+0xe1/0x370 kernel/fork.c:1582
 copy_process+0xe22/0x20d0 kernel/fork.c:2223
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2654
 __do_sys_clone kernel/fork.c:2795 [inline]
 __se_sys_clone kernel/fork.c:2779 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2779
 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+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 15858 Comm: dhcpcd-run-hook Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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