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BUG: KCSAN: data-race in copy_mm / percpu_counter_destroy_many

write to 0xffff8881034e8be8 of 8 bytes by task 10804 on cpu 0:
 __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]
 mmdrop_sched include/linux/sched/mm.h:83 [inline]
 mmdrop_lazy_tlb_sched include/linux/sched/mm.h:110 [inline]
 finish_task_switch+0x184/0x280 kernel/sched/core.c:5180
 context_switch kernel/sched/core.c:5301 [inline]
 __schedule+0x93c/0xd40 kernel/sched/core.c:6911
 preempt_schedule_common+0x11/0x30 kernel/sched/core.c:7095
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 vprintk_emit+0x5cb/0x600 kernel/printk/printk.c:2480
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __ext4_msg+0x1aa/0x1c0 fs/ext4/super.c:995
 ext4_print_free_blocks fs/ext4/inode.c:1788 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2513 [inline]
 ext4_do_writepages+0x1ed1/0x2840 fs/ext4/inode.c:2935
 ext4_writepages+0x18f/0x320 fs/ext4/inode.c:3029
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2575
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 file_write_and_wait_range+0x178/0x2f0 mm/filemap.c:786
 generic_buffers_fsync_noflush+0x45/0x130 fs/buffer.c:606
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x1e4/0x710 fs/ext4/fsync.c:159
 vfs_fsync_range+0xc5/0xe0 fs/sync.c:186
 generic_write_sync include/linux/fs.h:2640 [inline]
 ext4_buffered_write_iter+0x34f/0x3c0 fs/ext4/file.c:306
 ext4_file_write_iter+0x380/0xfa0 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x5a6/0x9f0 fs/read_write.c:688
 ksys_write+0xdc/0x1a0 fs/read_write.c:740
 __do_sys_write fs/read_write.c:751 [inline]
 __se_sys_write fs/read_write.c:748 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:748
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 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

read to 0xffff8881034e86c0 of 1664 bytes by task 10825 on cpu 1:
 dup_mm kernel/fork.c:1525 [inline]
 copy_mm+0xe1/0x370 kernel/fork.c:1583
 copy_process+0xe22/0x20b0 kernel/fork.c:2223
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2653
 __do_sys_clone kernel/fork.c:2794 [inline]
 __se_sys_clone kernel/fork.c:2778 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2778
 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: 1 UID: 0 PID: 10825 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 03/18/2026
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