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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff868e70f8 of 88 bytes by task 20546 on cpu 1:
 prb_reserve+0x76a/0xb60 kernel/printk/printk_ringbuffer.c:1690
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x610 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 __netdev_printk+0x310/0x370 net/core/dev.c:12909
 netdev_info+0x9b/0xd0 net/core/dev.c:12956
 __dev_set_promiscuity+0x1fb/0x3f0 net/core/dev.c:9546
 netif_set_promiscuity+0x39/0x90 net/core/dev.c:9581
 dev_set_promiscuity+0xc1/0x170 net/core/dev_api.c:287
 macsec_dev_change_rx_flags+0xf9/0x110 drivers/net/macsec.c:3647
 dev_change_rx_flags net/core/dev.c:9517 [inline]
 __dev_set_promiscuity+0x373/0x3f0 net/core/dev.c:9561
 __dev_change_flags+0x2aa/0x3c0 net/core/dev.c:9743
 rtnl_configure_link net/core/rtnetlink.c:3594 [inline]
 rtnl_newlink_create+0x36b/0x620 net/core/rtnetlink.c:3850
 __rtnl_newlink net/core/rtnetlink.c:3957 [inline]
 rtnl_newlink+0xf5b/0x1360 net/core/rtnetlink.c:4072
 rtnetlink_rcv_msg+0x5fe/0x6d0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2550
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6985
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg+0x145/0x180 net/socket.c:733
 ____sys_sendmsg+0x31e/0x4a0 net/socket.c:2583
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2637
 __sys_sendmsg net/socket.c:2669 [inline]
 __do_sys_sendmsg net/socket.c:2674 [inline]
 __se_sys_sendmsg net/socket.c:2672 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2672
 x64_sys_call+0x17ba/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff868e70f8 of 8 bytes by task 20556 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:2014 [inline]
 _prb_read_valid+0x383/0x920 kernel/printk/printk_ringbuffer.c:2171
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 printk_get_next_message+0xc8/0x510 kernel/printk/printk.c:2999
 console_emit_next_record kernel/printk/printk.c:3083 [inline]
 console_flush_one_record kernel/printk/printk.c:3215 [inline]
 console_flush_all+0x2c8/0x6f0 kernel/printk/printk.c:3289
 __console_flush_and_unlock kernel/printk/printk.c:3319 [inline]
 console_unlock+0xa1/0x2e0 kernel/printk/printk.c:3359
 vcs_read+0x869/0xa10 drivers/tty/vt/vc_screen.c:452
 vfs_read+0x1a8/0x770 fs/read_write.c:570
 ksys_pread64 fs/read_write.c:763 [inline]
 __do_sys_pread64 fs/read_write.c:771 [inline]
 __se_sys_pread64 fs/read_write.c:768 [inline]
 __x64_sys_pread64+0xfd/0x150 fs/read_write.c:768
 x64_sys_call+0x281b/0x3000 arch/x86/include/generated/asm/syscalls_64.h:18
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000006e55 -> 0x0000000000008e55

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 20556 Comm: syz.4.20550 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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