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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86c8ea38 of 8 bytes by task 49 on cpu 0:
 data_alloc+0x2fc/0x380 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __netdev_printk+0x310/0x370 net/core/dev.c:12966
 netdev_info+0xa6/0xd0 net/core/dev.c:13013
 __dev_set_promiscuity+0x1e5/0x3c0 net/core/dev.c:9614
 __dev_set_rx_mode+0x1e4/0x220 net/core/dev_addr_lists.c:1384
 dev_uc_del+0x144/0x160 net/core/dev_addr_lists.c:845
 macsec_dev_stop+0x37b/0x3c0 drivers/net/macsec.c:3668
 __dev_close_many+0x24d/0x460 net/core/dev.c:1776
 netif_close_many+0x101/0x2d0 net/core/dev.c:1802
 unregister_netdevice_many_notify+0x500/0x1550 net/core/dev.c:12410
 unregister_netdevice_many net/core/dev.c:12501 [inline]
 default_device_exit_batch+0x5d7/0x630 net/core/dev.c:13093
 ops_exit_list net/core/net_namespace.c:205 [inline]
 ops_undo_list+0x2ca/0x420 net/core/net_namespace.c:252
 cleanup_net+0x37c/0x5b0 net/core/net_namespace.c:702
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
 worker_thread+0x569/0x750 kernel/workqueue.c:3486
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff86c8ea38 of 16 bytes by task 28830 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1934 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1982 [inline]
 _prb_read_valid+0x183/0x930 kernel/printk/printk_ringbuffer.c:2173
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 __console_flush_and_unlock kernel/printk/printk.c:3392 [inline]
 console_unlock+0x146/0x280 kernel/printk/printk.c:3413
 class_console_lock_destructor include/linux/console.h:734 [inline]
 do_con_write+0x2a1e/0x2a80 drivers/tty/vt/vt.c:3339
 con_write+0x25/0x1d0 drivers/tty/vt/vt.c:3661
 process_output_block drivers/tty/n_tty.c:557 [inline]
 n_tty_write+0x7f4/0xb00 drivers/tty/n_tty.c:2366
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write+0x397/0x690 drivers/tty/tty_io.c:1081
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1102
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57d/0x990 fs/read_write.c:687
 ksys_write+0xdc/0x1a0 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:747
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 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: 28830 Comm: syz.5.6487 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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