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BUG: KCSAN: data-race in serial8250_do_startup / serial8250_modem_status

write to 0xffffffff88ea59d6 of 1 bytes by task 10204 on cpu 1:
 serial8250_do_startup+0x165e/0x1eb0 drivers/tty/serial/8250/8250_port.c:2460
 serial8250_startup+0x41/0x50 drivers/tty/serial/8250/8250_port.c:2482
 uart_port_startup drivers/tty/serial/serial_core.c:324 [inline]
 uart_startup+0x465/0x8e0 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:764
 uart_open+0x30/0x40 drivers/tty/serial/serial_core.c:1973
 tty_open+0x3d1/0xaf0 drivers/tty/tty_io.c:2137
 chrdev_open+0x2eb/0x3a0 fs/char_dev.c:414
 do_dentry_open+0x649/0xa20 fs/open.c:964
 vfs_open+0x37/0x1e0 fs/open.c:1094
 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: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+0x1af/0x2fb0 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 0xffffffff88ea59d6 of 1 bytes by interrupt on cpu 0:
 serial8250_modem_status+0x6a/0x1e0 drivers/tty/serial/8250/8250_port.c:1859
 serial8250_handle_irq+0x3d6/0x660 drivers/tty/serial/8250/8250_port.c:1943
 serial8250_default_handle_irq+0x8e/0x120 drivers/tty/serial/8250/8250_port.c:1966
 serial8250_interrupt+0x63/0x110 drivers/tty/serial/8250/8250_core.c:86
 __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+0x188/0x4f0 kernel/irq/chip.c:789
 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:266 [inline]
 __common_interrupt+0x60/0x100 arch/x86/kernel/irq.c:292
 common_interrupt+0x7e/0x90 arch/x86/kernel/irq.c:285
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
 kcsan_setup_watchpoint+0x415/0x430 kernel/kcsan/core.c:705
 jhash2 include/linux/jhash.h:126 [inline]
 hash_stack lib/stackdepot.c:514 [inline]
 stack_depot_save_flags+0x99/0xb60 lib/stackdepot.c:615
 stack_depot_save+0xe/0x20 lib/stackdepot.c:690
 ref_tracker_free+0xa3/0x3e0 lib/ref_tracker.c:240
 netdev_tracker_free include/linux/netdevice.h:4361 [inline]
 netdev_put include/linux/netdevice.h:4378 [inline]
 netdev_queue_release+0x47/0xa0 net/core/net-sysfs.c:1910
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0xef/0x190 lib/kobject.c:737
 netdev_queue_update_kobjects+0x45f/0x4d0 net/core/net-sysfs.c:2052
 remove_queue_kobjects net/core/net-sysfs.c:2149 [inline]
 netdev_unregister_kobject+0xcc/0x270 net/core/net-sysfs.c:2304
 unregister_netdevice_many_notify+0x1292/0x1690 net/core/dev.c:12112
 unregister_netdevice_many+0x19/0x20 net/core/dev.c:12140
 ops_exit_rtnl_list net/core/net_namespace.c:188 [inline]
 ops_undo_list+0x213/0x410 net/core/net_namespace.c:249
 cleanup_net+0x2de/0x4d0 net/core/net_namespace.c:686
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3321
 worker_thread+0x582/0x770 kernel/workqueue.c:3402
 kthread+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00 -> 0x05

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 1811 Comm: kworker/u8:6 Not tainted 6.16.0-rc1-syzkaller-00004-gaef17cb3d3c4 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: netns cleanup_net
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