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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86871ab0 of 8 bytes by task 21540 on cpu 0:
 data_alloc+0x271/0x2b0 kernel/printk/printk_ringbuffer.c:1095
 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4917
 dev_printk_emit+0x84/0xb0 drivers/base/core.c:4928
 __netdev_printk+0x35c/0x3e0 net/core/dev.c:12509
 netdev_info+0x9b/0xd0 net/core/dev.c:12564
 nsim_udp_tunnel_set_port+0x171/0x190 drivers/net/netdevsim/udp_tunnels.c:34
 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:246 [inline]
 __udp_tunnel_nic_device_sync+0x567/0x9c0 net/ipv4/udp_tunnel_nic.c:289
 udp_tunnel_nic_device_sync net/ipv4/udp_tunnel_nic.c:312 [inline]
 __udp_tunnel_nic_add_port+0x6a9/0x720 net/ipv4/udp_tunnel_nic.c:531
 udp_tunnel_nic_add_port include/net/udp_tunnel.h:365 [inline]
 udp_tunnel_notify_add_rx_port+0x12e/0x190 net/ipv4/udp_tunnel_core.c:143
 geneve_socket_create drivers/net/geneve.c:612 [inline]
 geneve_sock_add+0x3c2/0x5b0 drivers/net/geneve.c:687
 geneve_open+0x66/0xf0 drivers/net/geneve.c:723
 __dev_open+0x2d5/0x530 net/core/dev.c:1683
 __dev_change_flags+0x163/0x400 net/core/dev.c:9458
 rtnl_configure_link net/core/rtnetlink.c:3577 [inline]
 rtnl_newlink_create+0x36b/0x620 net/core/rtnetlink.c:3833
 __rtnl_newlink net/core/rtnetlink.c:3940 [inline]
 rtnl_newlink+0xf29/0x12d0 net/core/rtnetlink.c:4055
 rtnetlink_rcv_msg+0x5fe/0x6d0 net/core/rtnetlink.c:6944
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2552
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6971
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5a8/0x680 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x145/0x180 net/socket.c:727
 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2566
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2620
 __sys_sendmsg net/socket.c:2652 [inline]
 __do_sys_sendmsg net/socket.c:2657 [inline]
 __se_sys_sendmsg net/socket.c:2655 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2655
 x64_sys_call+0x2999/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:47
 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 0xffffffff86871ab0 of 16 bytes by task 21542 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2185
 printk_get_next_message+0xc8/0x510 kernel/printk/printk.c:3005
 console_emit_next_record kernel/printk/printk.c:3092 [inline]
 console_flush_all+0x290/0x730 kernel/printk/printk.c:3226
 __console_flush_and_unlock kernel/printk/printk.c:3285 [inline]
 console_unlock+0xa1/0x330 kernel/printk/printk.c:3325
 do_con_write+0x28d7/0x2940 drivers/tty/vt/vt.c:-1
 con_write+0x24/0x40 drivers/tty/vt/vt.c:3516
 do_output_char+0x49a/0x500 drivers/tty/n_tty.c:422
 __process_echoes+0x20d/0x6b0 drivers/tty/n_tty.c:701
 flush_echoes drivers/tty/n_tty.c:791 [inline]
 __receive_buf drivers/tty/n_tty.c:1626 [inline]
 n_tty_receive_buf_common+0x8e4/0xbe0 drivers/tty/n_tty.c:1723
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1769
 tty_ldisc_receive_buf+0x63/0xf0 drivers/tty/tty_buffer.c:387
 paste_selection+0x333/0x490 drivers/tty/vt/selection.c:446
 tioclinux+0x3b5/0x460 drivers/tty/vt/vt.c:3434
 vt_ioctl+0x75f/0x1880 drivers/tty/vt/vt_ioctl.c:761
 tty_ioctl+0x7de/0xb80 drivers/tty/tty_io.c:2792
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:893
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
 x64_sys_call+0x19a8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:17
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 21542 Comm: syz.1.6683 Not tainted 6.16.0-rc7-syzkaller-00034-g25fae0b93d1d #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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