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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff8688bba0 of 8 bytes by task 18495 on cpu 0:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x964/0xb60 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x610 kernel/printk/printk.c:2402
 dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4914
 dev_printk_emit+0x84/0xb0 drivers/base/core.c:4925
 __netdev_printk+0x34b/0x370 net/core/dev.c:12901
 netdev_info+0x9b/0xd0 net/core/dev.c:12956
 nsim_udp_tunnel_set_port+0x135/0x150 drivers/net/netdevsim/udp_tunnels.c:31
 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_device_sync_work+0x5d/0x580 net/ipv4/udp_tunnel_nic.c:740
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffffffff8688bba0 of 16 bytes by task 28500 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2170
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 __console_flush_and_unlock kernel/printk/printk.c:3338 [inline]
 console_unlock+0x164/0x2e0 kernel/printk/printk.c:3359
 class_console_lock_destructor include/linux/console.h:737 [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:459
 process_output drivers/tty/n_tty.c:482 [inline]
 n_tty_write+0x8d5/0xbf0 drivers/tty/n_tty.c:2377
 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
 do_iter_readv_writev+0x4a1/0x540 fs/read_write.c:-1
 vfs_writev+0x2df/0x8b0 fs/read_write.c:1057
 do_writev+0xe7/0x210 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __x64_sys_writev+0x45/0x50 fs/read_write.c:1168
 x64_sys_call+0x1ba5/0x3000 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 28500 Comm: syz.0.18953 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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