BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86927060 of 88 bytes by task 29 on cpu 0:
 prb_reserve+0x696/0xaf0 kernel/printk/printk_ringbuffer.c:1635
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 kauditd_printk_skb kernel/audit.c:583 [inline]
 kauditd_hold_skb+0x1b1/0x1c0 kernel/audit.c:618
 kauditd_send_queue+0x270/0x2c0 kernel/audit.c:803
 kauditd_thread+0x421/0x630 kernel/audit.c:927
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff86927060 of 8 bytes by task 4647 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1c4/0x920 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
 con_install+0x26b/0x2a0 drivers/tty/vt/vt.c:3629
 tty_driver_install_tty drivers/tty/tty_io.c:1295 [inline]
 tty_init_dev+0x7c/0x330 drivers/tty/tty_io.c:1407
 tty_open_by_driver drivers/tty/tty_io.c:2073 [inline]
 tty_open+0x6c7/0xaf0 drivers/tty/tty_io.c:2120
 chrdev_open+0x2eb/0x3a0 fs/char_dev.c:414
 do_dentry_open+0x649/0xa20 fs/open.c:965
 vfs_open+0x37/0x1e0 fs/open.c:1095
 do_open fs/namei.c:3975 [inline]
 path_openat+0x1c5e/0x2170 fs/namei.c:4134
 do_filp_open+0x109/0x230 fs/namei.c:4161
 do_sys_openat2+0xa6/0x110 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1461
 x64_sys_call+0x2eab/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
 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: 0x0000000000003a02 -> 0x0000000000005a02

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4647 Comm: syz.8.22653 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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