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BUG: KCSAN: data-race in serial8250_do_startup / serial8250_handle_irq

write to 0xffffffff88ec1e66 of 1 bytes by task 1426 on cpu 1:
 serial8250_do_startup+0x1491/0x1c10 drivers/tty/serial/8250/8250_port.c:2327
 serial8250_startup+0x41/0x50 drivers/tty/serial/8250/8250_port.c:2347
 uart_port_startup drivers/tty/serial/serial_core.c:321 [inline]
 uart_startup+0x468/0x8e0 drivers/tty/serial/serial_core.c:365
 uart_port_activate+0x67/0xc0 drivers/tty/serial/serial_core.c:1974
 tty_port_open+0x196/0x270 drivers/tty/tty_port.c:747
 uart_open+0x30/0x40 drivers/tty/serial/serial_core.c:1954
 tty_open+0x3d4/0xaf0 drivers/tty/tty_io.c:2137
 chrdev_open+0x2eb/0x3a0 fs/char_dev.c:414
 do_dentry_open+0x649/0xa20 fs/open.c:965
 vfs_open+0x37/0x1e0 fs/open.c:1097
 do_open fs/namei.c:3975 [inline]
 path_openat+0x1c5e/0x2170 fs/namei.c:4134
 do_filp_open+0x109/0x230 fs/namei.c:4161
 do_sys_openat2+0xa6/0x110 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1463
 x64_sys_call+0x2eab/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88ec1e66 of 1 bytes by interrupt on cpu 0:
 serial8250_handle_irq+0x3f9/0x660 drivers/tty/serial/8250/8250_port.c:1825
 serial8250_default_handle_irq+0x8e/0x170 drivers/tty/serial/8250/8250_port.c:1846
 serial8250_interrupt+0x63/0x130 drivers/tty/serial/8250/8250_core.c:82
 __handle_irq_event_percpu+0x9d/0x540 kernel/irq/handle.c:203
 handle_irq_event_percpu kernel/irq/handle.c:240 [inline]
 handle_irq_event+0x64/0xf0 kernel/irq/handle.c:257
 handle_edge_irq+0x154/0x470 kernel/irq/chip.c:855
 generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
 handle_irq arch/x86/kernel/irq.c:254 [inline]
 call_irq_handler arch/x86/kernel/irq.c:-1 [inline]
 __common_interrupt+0x60/0xb0 arch/x86/kernel/irq.c:325
 common_interrupt+0x7e/0x90 arch/x86/kernel/irq.c:318
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
 check_kcov_mode kernel/kcov.c:185 [inline]
 __sanitizer_cov_trace_pc+0x37/0x70 kernel/kcov.c:217
 folios_put_refs+0x1fb/0x2d0 mm/swap.c:957
 free_pages_and_swap_cache+0x278/0x400 mm/swap_state.c:355
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
 tlb_flush_mmu+0x2dc/0x450 mm/mmu_gather.c:404
 zap_pte_range mm/memory.c:1894 [inline]
 zap_pmd_range mm/memory.c:1947 [inline]
 zap_pud_range mm/memory.c:1976 [inline]
 zap_p4d_range mm/memory.c:1997 [inline]
 unmap_page_range+0x22c8/0x25c0 mm/memory.c:2018
 unmap_single_vma mm/memory.c:2061 [inline]
 unmap_vmas+0x23d/0x3a0 mm/memory.c:2105
 exit_mmap+0x1b0/0x6c0 mm/mmap.c:1280
 __mmput+0x28/0x1c0 kernel/fork.c:1133
 mmput+0x40/0x50 kernel/fork.c:1156
 exit_mm+0xe4/0x180 kernel/exit.c:582
 do_exit+0x417/0x15c0 kernel/exit.c:954
 do_group_exit+0xff/0x140 kernel/exit.c:1107
 get_signal+0xe58/0xf70 kernel/signal.c:3034
 arch_do_signal_or_restart+0x96/0x440 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x77/0x110 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0x05

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 1411 Comm: syz.0.10484 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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