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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff868eff68 of 88 bytes by task 29367 on cpu 1:
 prb_reserve+0x695/0xaf0 kernel/printk/printk_ringbuffer.c:1651
 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
 __nla_validate_parse+0x1738/0x1d00 lib/nlattr.c:647
 __nla_parse+0x40/0x60 lib/nlattr.c:732
 nla_parse_nested_deprecated include/net/netlink.h:1379 [inline]
 tcf_gact_init+0x112/0x510 net/sched/act_gact.c:74
 tcf_action_init_1+0x36a/0x4a0 net/sched/act_api.c:1431
 tcf_action_init+0x267/0x6d0 net/sched/act_api.c:1506
 tcf_action_add net/sched/act_api.c:2104 [inline]
 tc_ctl_action+0x291/0x830 net/sched/act_api.c:2161
 rtnetlink_rcv_msg+0x65a/0x6d0 net/core/rtnetlink.c:6960
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2552
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6978
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5c0/0x690 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+0x145/0x180 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 0xffffffff868eff68 of 8 bytes by task 29310 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:483 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1892 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1940 [inline]
 _prb_read_valid+0x1c4/0x920 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_shutdown+0x4b/0x60 drivers/tty/vt/vt.c:3697
 release_tty+0x85/0x4f0 drivers/tty/tty_io.c:1580
 tty_release_struct+0x96/0xb0 drivers/tty/tty_io.c:1692
 tty_release+0x856/0xb10 drivers/tty/tty_io.c:1852
 __fput+0x29b/0x650 fs/file_table.c:468
 ____fput+0x1c/0x30 fs/file_table.c:496
 task_work_run+0x131/0x1a0 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xed/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002ff5 -> 0x0000000000004ff5

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 29310 Comm: syz.8.19277 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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