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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff8686cb70 of 8 bytes by task 16915 on cpu 0:
 data_alloc+0x274/0x2e0 kernel/printk/printk_ringbuffer.c:1101
 prb_reserve+0x807/0xaf0 kernel/printk/printk_ringbuffer.c:1685
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299
 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2448
 vlan_check_real_dev+0x19d/0x1f0 net/8021q/vlan.c:135
 vlan_newlink+0x23d/0x370 net/8021q/vlan_netlink.c:176
 rtnl_newlink_create+0x1bc/0x620 net/core/rtnetlink.c:3833
 __rtnl_newlink net/core/rtnetlink.c:3950 [inline]
 rtnl_newlink+0xf29/0x12d0 net/core/rtnetlink.c:4065
 rtnetlink_rcv_msg+0x5fb/0x6d0 net/core/rtnetlink.c:6954
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2552
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6981
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5bd/0x690 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x142/0x180 net/socket.c:742
 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2630
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2684
 __sys_sendmsg net/socket.c:2716 [inline]
 __do_sys_sendmsg net/socket.c:2721 [inline]
 __se_sys_sendmsg net/socket.c:2719 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2719
 x64_sys_call+0x191e/0x3000 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 0xffffffff8686cb70 of 16 bytes by task 16931 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:479 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1892 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1940 [inline]
 _prb_read_valid+0x1bc/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]
 con_flush_chars+0xb2/0x1b0 drivers/tty/vt/vt.c:3636
 n_tty_write+0x93a/0xb40 drivers/tty/n_tty.c:2393
 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+0x527/0x960 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 16931 Comm: syz.0.4595 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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