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BUG: KCSAN: data-race in desc_read_finalized_seq / prb_reserve

write to 0xffffffff86702668 of 8 bytes by task 17669 on cpu 0:
 prb_reserve+0x740/0xb60
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x168/0x690 kernel/printk/printk.c:2408
 dev_vprintk_emit+0x23c/0x2a0 drivers/base/core.c:4891
 dev_printk_emit+0x82/0xb0 drivers/base/core.c:4902
 __netdev_printk+0x352/0x3e0 net/core/dev.c:12299
 netdev_info+0x99/0xc0 net/core/dev.c:12354
 nsim_udp_tunnel_unset_port+0x1bc/0x1e0 drivers/net/netdevsim/udp_tunnels.c:64
 udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:246 [inline]
 __udp_tunnel_nic_device_sync+0x57b/0x9e0 net/ipv4/udp_tunnel_nic.c:289
 udp_tunnel_nic_flush+0x22c/0x320 net/ipv4/udp_tunnel_nic.c:670
 udp_tunnel_nic_unregister net/ipv4/udp_tunnel_nic.c:864 [inline]
 udp_tunnel_nic_netdevice_event+0x7b9/0xc80 net/ipv4/udp_tunnel_nic.c:904
 notifier_call_chain kernel/notifier.c:85 [inline]
 raw_notifier_call_chain+0x6f/0x1d0 kernel/notifier.c:453
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:2206
 call_netdevice_notifiers_extack net/core/dev.c:2244 [inline]
 call_netdevice_notifiers net/core/dev.c:2258 [inline]
 unregister_netdevice_many_notify+0x98a/0x1280 net/core/dev.c:11887
 unregister_netdevice_many net/core/dev.c:11951 [inline]
 unregister_netdevice_queue+0x1f4/0x220 net/core/dev.c:11821
 unregister_netdevice include/linux/netdevice.h:3337 [inline]
 nsim_destroy+0xbd/0x330 drivers/net/netdevsim/netdev.c:1021
 __nsim_dev_port_del+0xcd/0x100 drivers/net/netdevsim/dev.c:1428
 nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1440 [inline]
 nsim_dev_reload_destroy+0x1a6/0x2d0 drivers/net/netdevsim/dev.c:1661
 nsim_dev_reload_down+0x77/0xa0 drivers/net/netdevsim/dev.c:968
 devlink_reload+0xab/0x5a0 net/devlink/dev.c:461
 devlink_pernet_pre_exit+0xd7/0x220 net/devlink/core.c:509
 ops_pre_exit_list net/core/net_namespace.c:162 [inline]
 cleanup_net+0x34e/0x890 net/core/net_namespace.c:632
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4db/0xa20 kernel/workqueue.c:3319
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3400
 kthread+0x4ae/0x520 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffffff86702668 of 8 bytes by task 7912 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq+0x157/0x280 kernel/printk/printk_ringbuffer.c:1874
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x140/0x6c0 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3d/0x60 kernel/printk/printk_ringbuffer.c:2182
 printk_get_next_message+0xd8/0x530 kernel/printk/printk.c:2989
 console_emit_next_record kernel/printk/printk.c:3076 [inline]
 console_flush_all+0x2a7/0x790 kernel/printk/printk.c:3210
 __console_flush_and_unlock kernel/printk/printk.c:3269 [inline]
 console_unlock+0xb6/0x340 kernel/printk/printk.c:3309
 con_flush_chars+0xb0/0x1b0 drivers/tty/vt/vt.c:3503
 con_write+0x30/0x40 drivers/tty/vt/vt.c:3433
 process_output_block drivers/tty/n_tty.c:574 [inline]
 n_tty_write+0x843/0xb80 drivers/tty/n_tty.c:2389
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write+0x37a/0x680 drivers/tty/tty_io.c:1090
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1111
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x77b/0x920 fs/read_write.c:679
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000033d1 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7912 Comm: syz.2.12125 Tainted: G        W          6.14.0-rc7-syzkaller-00196-g88d324e69ea9 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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