syzbot

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BUG: KCSAN: data-race in serial8250_do_startup / serial8250_handle_irq

write to 0xffffffff88e8dae6 of 1 bytes by task 20735 on cpu 1:
 serial8250_do_startup+0x13de/0x1b10 drivers/tty/serial/8250/8250_port.c:2366
 serial8250_startup+0x41/0x50 drivers/tty/serial/8250/8250_port.c:2388
 uart_port_startup drivers/tty/serial/serial_core.c:324 [inline]
 uart_startup+0x468/0x8e0 drivers/tty/serial/serial_core.c:368
 uart_port_activate+0x67/0xc0 drivers/tty/serial/serial_core.c:1993
 tty_port_open+0x145/0x1d0 drivers/tty/tty_port.c:763
 uart_open+0x30/0x40 drivers/tty/serial/serial_core.c:1973
 tty_open+0x3d1/0xaf0 drivers/tty/tty_io.c:2137
 chrdev_open+0x2e8/0x3a0 fs/char_dev.c:414
 do_dentry_open+0x649/0xa20 fs/open.c:965
 vfs_open+0x37/0x1e0 fs/open.c:1095
 do_open fs/namei.c:3887 [inline]
 path_openat+0x1c5e/0x2170 fs/namei.c:4046
 do_filp_open+0x109/0x230 fs/namei.c:4073
 do_sys_openat2+0xa6/0x110 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1461
 x64_sys_call+0x2e9c/0x2ff0 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 0xffffffff88e8dae6 of 1 bytes by interrupt on cpu 0:
 serial8250_handle_irq+0x3f9/0x660 drivers/tty/serial/8250/8250_port.c:1834
 serial8250_default_handle_irq+0x8e/0x140 drivers/tty/serial/8250/8250_port.c:1856
 serial8250_interrupt+0x63/0x110 drivers/tty/serial/8250/8250_core.c:82
 __handle_irq_event_percpu+0x90/0x440 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0x64/0xf0 kernel/irq/handle.c:210
 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:693
 arch_atomic64_read arch/x86/include/asm/atomic64_64.h:15 [inline]
 raw_atomic64_read include/linux/atomic/atomic-arch-fallback.h:2583 [inline]
 raw_atomic_long_read include/linux/atomic/atomic-long.h:38 [inline]
 atomic_long_read include/linux/atomic/atomic-instrumented.h:3189 [inline]
 find_watchpoint kernel/kcsan/core.c:131 [inline]
 check_access kernel/kcsan/core.c:737 [inline]
 __tsan_read8+0x39/0x190 kernel/kcsan/core.c:1025
 folio_mapping+0xa1/0x120 mm/util.c:702
 folio_needs_release mm/internal.h:521 [inline]
 truncate_cleanup_folio+0x8d/0x1f0 mm/truncate.c:159
 truncate_inode_folio+0x3a/0x50 mm/truncate.c:175
 shmem_undo_range+0x244/0xa80 mm/shmem.c:1153
 shmem_truncate_range mm/shmem.c:1269 [inline]
 shmem_evict_inode+0x134/0x520 mm/shmem.c:1397
 evict+0x2e0/0x550 fs/inode.c:810
 iput_final fs/inode.c:1897 [inline]
 iput+0x447/0x5b0 fs/inode.c:1923
 dentry_unlink_inode+0x24f/0x260 fs/dcache.c:466
 __dentry_kill+0x18d/0x4b0 fs/dcache.c:669
 dput+0x5e/0xd0 fs/dcache.c:911
 __fput+0x444/0x650 fs/file_table.c:476
 ____fput+0x1c/0x30 fs/file_table.c:496
 task_work_run+0x12e/0x1a0 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x483/0x15c0 kernel/exit.c:961
 do_group_exit+0xff/0x140 kernel/exit.c:1102
 get_signal+0xe59/0xf70 kernel/signal.c:3034
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:40 [inline]
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 irqentry_exit_to_user_mode+0x5e/0xa0 kernel/entry/common.c:73
 irqentry_exit+0x12/0x50 kernel/entry/common.c:177
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

value changed: 0x00 -> 0x05

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 20619 Comm: syz.1.4928 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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