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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff868f3b40 of 88 bytes by task 10965 on cpu 0:
 prb_reserve+0x695/0xaf0 kernel/printk/printk_ringbuffer.c:1651
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299
 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399
 dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4914
 dev_printk_emit+0x84/0xb0 drivers/base/core.c:4925
 __netdev_printk+0x35c/0x3e0 net/core/dev.c:12716
 netdev_info+0x9b/0xd0 net/core/dev.c:12771
 nsim_udp_tunnel_unset_port+0x18a/0x1b0 drivers/net/netdevsim/udp_tunnels.c:59
 udp_tunnel_nic_device_sync_one net/ipv4/udp_tunnel_nic.c:-1 [inline]
 udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:249 [inline]
 __udp_tunnel_nic_device_sync+0x567/0x9c0 net/ipv4/udp_tunnel_nic.c:292
 udp_tunnel_nic_flush+0x21b/0x300 net/ipv4/udp_tunnel_nic.c:694
 udp_tunnel_nic_unregister net/ipv4/udp_tunnel_nic.c:901 [inline]
 udp_tunnel_nic_netdevice_event+0x8ea/0xdd0 net/ipv4/udp_tunnel_nic.c:942
 notifier_call_chain kernel/notifier.c:85 [inline]
 raw_notifier_call_chain+0x6f/0x1b0 kernel/notifier.c:453
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:2229
 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
 call_netdevice_notifiers net/core/dev.c:2281 [inline]
 unregister_netdevice_many_notify+0xe76/0x1690 net/core/dev.c:12284
 unregister_netdevice_many net/core/dev.c:12347 [inline]
 unregister_netdevice_queue+0x1f5/0x220 net/core/dev.c:12161
 unregister_netdevice include/linux/netdevice.h:3389 [inline]
 nsim_destroy+0xfa/0x2f0 drivers/net/netdevsim/netdev.c:1178
 __nsim_dev_port_del+0xcf/0x110 drivers/net/netdevsim/dev.c:1473
 nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1485 [inline]
 nsim_dev_reload_destroy+0x1a3/0x2c0 drivers/net/netdevsim/dev.c:1707
 nsim_drv_remove+0x3e/0x110 drivers/net/netdevsim/dev.c:1722
 nsim_bus_remove+0x15/0x20 drivers/net/netdevsim/bus.c:419
 device_remove drivers/base/dd.c:569 [inline]
 __device_release_driver drivers/base/dd.c:1274 [inline]
 device_release_driver_internal+0x2be/0x4e0 drivers/base/dd.c:1297
 device_release_driver+0x19/0x20 drivers/base/dd.c:1320
 bus_remove_device+0x26d/0x290 drivers/base/bus.c:579
 device_del+0x36a/0x790 drivers/base/core.c:3878
 device_unregister+0x15/0x40 drivers/base/core.c:3919
 nsim_bus_dev_del drivers/net/netdevsim/bus.c:483 [inline]
 del_device_store+0x1c1/0x220 drivers/net/netdevsim/bus.c:244
 bus_attr_store+0x57/0x80 drivers/base/bus.c:172
 sysfs_kf_write+0xfe/0x120 fs/sysfs/file.c:142
 kernfs_fop_write_iter+0x1eb/0x300 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x52a/0x960 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2802/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 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 0xffffffff868f3b40 of 8 bytes by task 11253 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:483 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1892 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1940 [inline]
 _prb_read_valid+0x1c4/0x920 kernel/printk/printk_ringbuffer.c:2131
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2203
 __console_flush_and_unlock kernel/printk/printk.c:3277 [inline]
 console_unlock+0x164/0x2e0 kernel/printk/printk.c:3298
 class_console_lock_destructor include/linux/console.h:669 [inline]
 do_con_write+0x28df/0x2940 drivers/tty/vt/vt.c:3243
 con_put_char+0x38/0x60 drivers/tty/vt/vt.c:3573
 tty_put_char+0x68/0xc0 drivers/tty/tty_io.c:3153
 do_output_char+0x4de/0x500 drivers/tty/n_tty.c:463
 process_output drivers/tty/n_tty.c:486 [inline]
 n_tty_write+0x869/0xb40 drivers/tty/n_tty.c:2388
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write+0x378/0x690 drivers/tty/tty_io.c:1081
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1102
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x52a/0x960 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2802/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 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

value changed: 0x00000000000030a6 -> 0x00000000000050a6

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 11253 Comm: syz.8.11287 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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