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BUG: KCSAN: data-race in desc_read_finalized_seq / prb_reserve

write to 0xffffffff866d6760 of 8 bytes by task 25760 on cpu 0:
 prb_reserve+0x740/0xb60
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x168/0x690 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 __netdev_printk+0x2d1/0x3e0 net/core/dev.c:12224
 netdev_info+0x99/0xc0 net/core/dev.c:12271
 __tun_chr_ioctl+0xc17/0x1800 drivers/net/tun.c:3160
 tun_chr_ioctl+0x27/0x30 drivers/net/tun.c:3418
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff866d6760 of 8 bytes by task 25757 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq+0x157/0x280 kernel/printk/printk_ringbuffer.c:1874
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x140/0x6c0 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3d/0x60 kernel/printk/printk_ringbuffer.c:2182
 printk_get_next_message+0xd8/0x530 kernel/printk/printk.c:2989
 console_emit_next_record kernel/printk/printk.c:3076 [inline]
 console_flush_all+0x2a7/0x790 kernel/printk/printk.c:3210
 __console_flush_and_unlock kernel/printk/printk.c:3269 [inline]
 console_unlock+0xb6/0x340 kernel/printk/printk.c:3309
 do_con_write+0x2582/0x25f0
 con_write+0x26/0x40 drivers/tty/vt/vt.c:3432
 process_output_block drivers/tty/n_tty.c:574 [inline]
 n_tty_write+0x843/0xb80 drivers/tty/n_tty.c:2389
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write+0x37a/0x680 drivers/tty/tty_io.c:1090
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1111
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x77b/0x920 fs/read_write.c:679
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002bd6 -> 0x0000000000004bd6

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 25757 Comm: syz.7.7856 Tainted: G        W          6.14.0-rc3-syzkaller-00012-g2408a807bfc3 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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